Operation and repair of cable lines. Repair of power cable and installation of cable boxes Definition of reconstruction of cable lines

Monitoring the technical condition of cable lines

The operation of cable lines has its own characteristics, since it is not always possible to detect defects in it by simple inspection. Therefore, the condition of the insulation is checked, the load and temperature of the cable are monitored.

From the point of view of insulation testing, cables are the most difficult element of electrical equipment. This is due to the possible long length of cable lines, the heterogeneity of the soil along the length of the line, the heterogeneity of the cable insulation.

To detect gross defects in cable lines, they are produced at a voltage of 2500 V. However, the readings of the megohmmeter cannot serve as the basis for the final assessment of the state of insulation, since they are largely dependent on the length of the cable line and the defects of the terminations.

This is due to the fact that the capacitance of the power cable is large and during the time of measuring the resistance it does not have time to fully charge, so the megohmmeter readings will be determined not only by the steady leakage current, but also by the charging current, and the measured insulation resistance value will be significantly underestimated.

The main method for monitoring the condition of cable line insulation is. The purpose of testing is to identify and timely eliminate developing defects in cable insulation, sleeves and terminations in order to prevent damage during operation. At the same time, cables with voltages up to 1 kV are not tested with increased voltage, but the insulation resistance is measured with a megohmmeter with a voltage of 2500 V for 1 min. It must be at least 0.5 MΩ.

Checking short cable lines within one switchgear is carried out no more than once a year, since they are less susceptible to mechanical damage and their condition is more often monitored by personnel. The high voltage test of cable lines over 1 kV is carried out at least once every 3 years.

The main method for testing the insulation of cable lines is DC overvoltage test. This is due to the fact that the installation on alternating current, under equal conditions, has a much greater power.

The test setup includes: transformer, rectifier, voltage regulator, kilovoltmeter, microammeter.

When checking the insulation, the voltage from a megohmmeter or test facility is supplied to one of the cable cores, while the remaining cable cores are securely connected to each other and grounded. The voltage gradually rises to the normalized value and the required time is maintained.

The condition of the cable is determined by the leakage current. If it is in a satisfactory condition, the rise in voltage is accompanied by a sharp increase in the leakage current due to the charging of the capacitance, then it decreases to 10 - 20% of the maximum value. The cable line is considered serviceable if during the tests there was no breakdown or overlap on the surface of the end sleeve, there are no sharp surges of current and a noticeable increase in leakage current.

Cable overloads that are systematic, lead to a deterioration in insulation and a reduction in the duration of the line. Underloads are associated with underutilization of the conductor material. Therefore, during the operation of the cable line, it is periodically checked that the current load in them corresponds to that established when the facility was put into operation. The maximum allowable cable loads are determined by the requirements.

The loads of cable lines are monitored within the time limits determined by the chief power engineer of the enterprise, but at least 2 times a year. In this case, once the specified control is carried out during the period of the autumn-winter maximum load. Control is carried out by monitoring the readings of ammeters at supply substations, and in their absence, using portable devices or.

Permissible current loads for long-term normal operation of cable lines are determined using the tables given in electrical reference books. These loads depend on the cable laying method and the type of cooling medium (earth, air).

For cables laid in the ground, the long-term permissible load is taken from the calculation of laying one cable in a trench at a depth of 0.7 - 1 m at an earth temperature of 15 ° C. For cables laid outdoors, the ambient temperature is assumed to be 25°C. If the calculated ambient temperature differs from the accepted conditions, a correction factor is entered.

The highest average monthly temperature of all months of the year at the depth of the cable laying is taken as the design ground temperature.

The highest average daily temperature, repeated at least three times a year, is taken as the design air temperature.

The long-term permissible load of the cable line is determined by sections of lines with the worst cooling conditions, if the length of this section is at least 10 m. Cable lines up to 10 kV with a preload factor of not more than 0.6 - 0.8 can be overloaded for a short time. Permissible overload rates, taking into account their duration, are given in the technical literature.

For a more accurate determination of the load capacity, as well as when changing the temperature conditions of operation, cable line temperature control. It is impossible to directly control the temperature of the conductor on a working cable, since the conductors are energized. Therefore, at the same time, the temperature of the sheath (armor) of the cable and the load current are measured, and then the core temperature and the maximum allowable current load are determined by recalculation.

Measurement of the temperature of the metal sheaths of an openly laid cable is carried out with conventional thermometers, which are mounted on the armor or lead sheath of the cable. If the cable is laid in the ground, the measurement is made using thermocouples. It is recommended to install at least two sensors. Wires from thermocouples are laid in a pipe and removed to a convenient and safe place from mechanical damage.

The temperature of the conductor must not exceed:

for cables with paper insulation up to 1 kV - 80 ° C, up to 10 kV - 60 ° C;

for cables with rubber insulation - 65 ° С;

for cables in a PVC sheath - 65 ° C.

In the event that the current-carrying conductors of the cable are heated above the permissible temperature, measures are taken to eliminate overheating - reduce the load, improve ventilation, replace the cable with a cable of a larger cross section, increase the distance between the cables.

When laying cable lines in soil that is aggressive towards their metal sheaths (salt marshes, swamps, construction waste), soil corrosion of lead sheaths and metal cladding. In such cases, periodically check corrosivity soil by taking water and soil samples. If at the same time it is established that the degree of soil corrosion threatens the integrity of the cable, then appropriate measures are taken - the pollution is eliminated, the soil is replaced, etc.

Determination of cable line damage points

Determining the places of damage to cable lines is a rather difficult task and requires the use of special equipment. Work on the elimination of damage to the cable line begins with determining the type of damage. In many cases, this can be done with a megohmmeter. For this purpose, from both ends of the cable, the condition of the insulation of each core with respect to the ground, the serviceability of the insulation between the individual phases, and the absence of breaks in the cores are checked.

Determining the location of the damage is usually carried out in two stages - first, the damage zone is determined with an accuracy of 10 - 40 m, and then the location of the defect on the route is specified.

When determining the zone of damage, the causes of its occurrence and the consequences of failure are taken into account. Most often, there is a break in one or more conductors with or without grounding them; During preventive tests, most often there is a short circuit of the current-carrying core to the ground, as well as a floating breakdown.

To determine the damage zone, several methods are used: pulsed, oscillatory discharge, loop, capacitive.

Pulse method it is used for single-phase and interphase short circuits, as well as for wire breakage. The method of oscillatory discharge is resorted to with a floating breakdown (occurs at high voltage, disappears at low). The loop method is used for one-, two- and three-phase short circuits and the presence of at least one intact core. The capacitive method is used for wire breaks. In practice, the first two methods are most widely used.

When using the pulse method, fairly simple devices are used. To determine the zone of damage from them, short-term pulses of alternating current are sent to the cable. Having reached the place of damage, they are reflected and returned back. The nature of the cable damage is judged by the image on the screen of the device. The distance to the damage site can be determined by knowing the pulse travel time and the speed of its propagation.

The use of the pulse method requires a decrease in the contact resistance at the fault site to tens and even fractions of an ohm. For this purpose, the insulation is burned through by converting the electrical energy supplied to the damage site into thermal energy. Burning is carried out by direct or alternating current from special installations.

Oscillatory discharge method is that the damaged core of the cable is charged from the rectifier device to the breakdown voltage. At the moment of breakdown, an oscillatory process occurs in the cable. The oscillation period of this discharge corresponds to the time of a two-fold wave travel to the damage site and back.

The duration of the oscillatory discharge is measured with an oscilloscope or an electronic millisecond meter. The error of measurements by this method is 5%.

Specify the location of cable damage directly on the route using an acoustic or induction method.

acoustic method is based on fixing ground vibrations above the place of damage to the cable, caused by a spark discharge in the place of insulation failure. The method is used for damages of the "floating breakdown" type and breakage of the cores. In this case, damage is determined in the cable located at a depth of up to 3 m and under water up to 6 m.

As a pulse generator, a high-voltage direct current installation is usually used, from which pulses are sent to the cable. Ground vibrations are monitored by a special device. The disadvantage of the method is the need to use mobile DC installations.

Induction method Finding places of cable damage is based on fixing the nature of changes in the electromagnetic field above the cable, through the veins of which a high-frequency current is passed. The operator, moving along the route and using a loop antenna, amplifier and headphones, determines the location of the damage. The accuracy of determining the location of the damage is quite high and is 0.5 m. The same method can be used to establish the route of the cable line and the depth of the cables.

Cable repair

Repair of cable lines is carried out according to the results of inspections and tests. A feature of the work is the fact that the cables to be repaired may be energized, and in addition, they may be located close to the active cables under voltage. Therefore, personal safety must be observed, nearby cables must not be damaged.

Repair of cable lines may be associated with excavations. To avoid damage to nearby cables and utilities at a depth of more than 0.4 m, earthworks are carried out only with a shovel. If any cables or underground communications are found, work is stopped and the person responsible for the work is notified. After opening, care must be taken not to damage the cable and couplings. For this purpose, a solid board is placed under it.

The main types of work in case of damage to the cable line are: repair of armor cover, repair of shells, couplings and end fittings.

If there are local breaks in the armor, its ends are cut off at the defect site, soldered with a lead sheath and covered with an anti-corrosion coating (bitumen-based varnish).

When repairing the lead sheath, the possibility of moisture ingress into the cable is taken into account. To check the damaged area is immersed in paraffin heated to 150 ° C. In the presence of moisture, the dive will be accompanied by crackling and the release of yen. If the presence of moisture is established, then the damaged area is cut out and two couplings are mounted, otherwise the lead sheath is restored by applying a cut lead pipe to the damaged area and then sealing it.

For cables up to 1 kV, cast-iron couplings were previously used. They are bulky, expensive, and lack reliability. On 6 and 10 kV cable lines, epoxy and lead sleeves are mainly used. Currently, when repairing cable lines, they are actively used modern heat-shrink sleeves. There is a well developed technology for installing cable glands. The work is carried out by qualified personnel who have undergone appropriate training.

End couplings are divided into couplings installed indoors and outdoors. In the premises, dry cutting is more often done, it is more reliable and convenient to use. End sleeves in the open air are made in the form of a funnel made of roofing iron and filled with mastic. When carrying out current repairs, the condition of the end funnel is checked, the absence of leakage of the filling mass, it is topped up.

During the operation of cable lines (KL), damage may occur in cables, couplings or terminations. Damage is in the nature of an electrical breakdown.

During the current repair, KL perform the following work: inspection and cleaning of cable channels, tunnels, routes of openly laid cables, end funnels, couplings, straightening of cables, restoration of lost markings, determination of cable heating temperature and control of cable sheath corrosion; grounding check and elimination of detected defects; checking access to cable wells and serviceability of well covers and constipation on them; relocation of individual sections of the cable network, testing with increased voltage (for cables with voltages above 1 kV or checking insulation with a megohmmeter for cables below 1 kV), topping up funnels and couplings with cable mastic, repairing cable channels.

During the overhaul of cable lines, they perform: partial or complete replacement (as necessary) of sections of the cable network, coloring of cable structures, re-cutting of individual end funnels, cable couplings, replacement of identification marks, additional mechanical protection in places of possible damage to the cable.

Repair of cables laid in trenches. If it is necessary to replace the CL or part of it, the opening of improved coatings is carried out with S-850 electric concrete or S-849 electric hammer, S-329 motoconcrete, S-358 pneumoconcrete.

The coating material is dropped onto one side of the trench at a distance of at least 500 mm from the edge, and the soil on the other side - at a distance of at least 500 mm from the edge. The trench is dug straight, and at the corners - expanded to ensure the laying of cables with the required radius of curvature.

Trenches, in the absence of groundwater and underground structures, are dug without attaching vertical walls to the depth indicated below (in m):

In sandy soils ............................................................... .............................................1

In sandy loam .................................................. ................................................. .........1.25

In loams, clays ............................................... ...............................................1.5

In particularly dense soils .............................................. ................................................2

Trenches in places of movement of people and vehicles are fenced off and warning signs are installed near them, and at night - additional signal lighting. The distance between the fence and the axis of the nearest rail of the normal gauge railway track must be at least 2.5 m, and for narrow gauge - at least 2 m.

Before laying new cables in a trench, the following work is performed: pipes are fixed in a trench at the intersections and convergences of the route with roads, underground utilities and structures; remove water, stones and other objects from the trench and level its bottom; make a backfill 100 mm thick at the bottom of the trench with fine earth and prepare fine earth along the route for powdering the cable after laying; prepare bricks or reinforced concrete slabs along the route to protect the cable when such protection is needed. Materials subject to decay and decomposition in the ground (wood, sand-lime brick, etc.) cannot be used to protect cables.

In places of intersection and convergence with engineering structures, concrete, reinforced concrete, ceramic, cast iron or plastic pipes are used. Steel pipes are used only for the passage of a section of the route by the pound puncture method.

The laying depth for cables with voltage up to 10 kV from the planning mark should be 0.7 m. Before laying the cable, an external inspection of the upper turns of the cable on the drum is carried out. In case of detection of damage (dents, punctures on the turns, cracks in the “kappa”, etc.), cable laying is allowed only after cutting out the damaged places, checking the insulation for the absence of moisture and soldering new kappas to the ends of the cable. During repair work, the rolling of the cable from the drum is most often performed using a winch.

Cables are laid with a margin equal to 1-3% of its length (snake), in order to eliminate dangerous mechanical stresses during soil displacements and temperature deformations, cable laying with a snake when pulled by a winch is performed after the end of rolling from the drum in the process of laying the cable to the bottom of the trench. When cables are laid in parallel in a trench, their ends, intended for subsequent installation of couplings, are located with a shift of the joints by at least 2 m. , protecting the couplings from damage in case of possible displacements of the soil and temperature deformations of the cable, as well as in case of redistribution of the couplings if they are damaged.

In cramped conditions with large flows of existing cables, expansion joints can be placed in a vertical plane, placing the couplings below the cable laying level. The number of couplings per 1 km of replaced cable lines should be no more than 4 pcs of three-core cables 1-10 kV with a cross section of up to 3 x 95 mm2, and 5 pcs with a cross section of 3 x 95 * 2 x 240 mm2.

6. REPAIR OF CABLE LINES

6.1. General repair instructions

During the operation of cable lines, for certain reasons, cables, as well as couplings and terminations, fail. The main causes of damage to cable lines with a voltage of 1 ... 10 kV are as follows:

Previous mechanical damage - 43%;

Direct mechanical damage by construction and other organizations - 16%;

Defects in couplings and terminations during installation - 10%;

Damage to the cable and couplings as a result of soil settlement - 8%;

Corrosion of metal sheaths of cables - 7%;

Defects in cable manufacturing at the factory - 5%;

Violations during cable laying - 3%;

Insulation aging due to long-term operation or overloads - 1%;

Other and unidentified causes - 7%.

In accordance with the requirements of the Operating Instructions for power cable lines, maintenance or overhaul of cable lines with voltage up to 35 kV is provided. Current repairs can be emergency, urgent and planned.

Emergency repair is necessary when, after disconnecting the cable line, consumers of all categories are left without voltage and it is not possible to supply voltage through high or low voltage cables, including temporary hose cables, or when the backup line to which the load is transferred is unacceptably overloaded and consumption restrictions are required. Emergency repairs are started immediately and carried out continuously in order to turn on the cable line in the shortest possible time.

In large urban cable networks and at large industrial enterprises, for this purpose, emergency recovery services have been formed from a brigade or several teams that are on duty around the clock and, at the direction of the dispatch service, immediately go to the accident site.

Urgent repair is required if category 1 or 2 receivers lose automatic backup power and the remaining cable lines are overloaded, leading to a limitation in consumption. At the direction of the management of the energy service, repair teams begin urgent repairs of cable lines during the work shift.

Scheduled repairs are carried out according to the schedule approved by the management of the energy service. The schedule for repairing cable lines is compiled monthly based on entries in the logs of rounds and inspections, test and measurement results, as well as data from dispatch services.

Overhaul of cable lines is carried out according to the annual plan, developed annually in the summer for the next year based on operating data. When drawing up a major overhaul plan, the need to introduce new, more modern types of cables and cable accessories is taken into account. It is planned to repair cable structures and eliminate malfunctions in lighting, ventilation, fire fighting equipment, and water pumping devices. It also takes into account the need for partial replacement of cables in individual sections that limit the capacity of the lines or do not meet the requirements for thermal stability in the changed conditions of the network with increased short-circuit currents.

Repair of cable lines in operation is carried out directly by the operating personnel themselves or by personnel of specialized electrical installation organizations. During the repair of operated cable lines, the following work is performed:

Disconnection of the cable line and its grounding, familiarization with the documentation and clarification of the brand and section of the cable, issuance of a work permit for safety, loading of materials and tools, delivery of the team to the place of work;

Excavation of pits, excavation of pits and trenches, determination of the cable to be repaired, fencing of the workplace and excavation sites, determination of the cable in the RP (TP) or in cable structures, checking the absence of flammable and explosive gases, obtaining a permit for hot work;

Crew approval, cable puncture, cutting the cable or opening the sleeve, checking the insulation for moisture, cutting off sections of damaged cable, setting up a tent;

Laying a repair cable insert;

Repair of the cable sleeve - cutting the ends of the cable, phasing cables, installation of couplings (or couplings and terminations);

Completion of work - closing the doors of the switchgear, transformer substation, cable structures, handing over keys, backfilling pits and trenches, cleaning and loading tools, delivering the team to the base, drawing up an executive sketch and making changes to the cable line documentation, report on the completion of repairs;

Cable line measurements and tests.

In order to speed up repair work on cable lines, pneumatic jackhammers, electric hammers, concrete breakers, excavators, and means for thawing frozen soil should be used.

Repair work of cable lines can be simple, not requiring much labor and time, and complex, lasting several days. Simple repairs include, for example, such as repair of external covers (jute cover, PVC hose), painting and repair of armored tapes, repair of metal shells, repair of end fittings without dismantling the hull, etc. Simple repairs are performed in one shift by one team (link ).

More difficult repairs involve the replacement of a large length of cable in cable structures with the preliminary dismantling of a failed cable or the laying of a new cable in the ground in a section several tens of meters long (in rare cases, hundreds of meters). Repairs are hindered by the laying of a cable route through complex sections with many turns, with the intersection of highways and utilities, the large depth of the cable, and the need to warm the earth in winter. When performing complex repairs, a new section of the cable (insert) is laid and two couplings are mounted.

Complicated repairs are carried out by one or more teams, and if necessary - around the clock and with the use of earthmoving mechanisms and other mechanization. Complex repairs are carried out either by the energy service of the enterprise (city networks), or with the involvement of specialized organizations for the installation and repair of cable lines.

6.2. Repair of protective covers

Repair of the outer jute cover. The frayed impregnated cable yarn of the cable pulled through pipes, blocks or other obstacles must be restored. The repair is carried out by winding with resin tape in two layers with a 50% overlap, followed by lubrication of this area with heated MB-70 (MB-90) bituminous mastic.

Repair of PVC hose and sheaths. Repair of a PVC hose or sheaths is carried out by welding, in a stream of hot air (at a temperature of 170 ... ... 200 ° C) using a welding gun with electric air heating, as shown in fig. 6.1, gas-air - in fig. 6.2. Compressed air is supplied at a pressure of 0.98×10 4 Pa ​​from a compressor, a cylinder of compressed air or a portable unit with a hand pump.

Figure 6.1. Welding gun PS-1 with electric heating:

1 2 - heating air chamber;

3 - fitting for compressed air supply; 4 - electric wire

Rice. 6.2. Air gun:

1 - a nozzle for an exit of hot air; 2 - heating air

camera; 3 - rubber tube; 4- faucet for air;

5- faucet for propane-butane; 6 - fitting for compressed air supply;

7 - fitting for supplying propane-butane

As an additive in welding, a PVC rod with a diameter of 4 ... 6 mm is used.

Before welding, the places to be repaired must be cleaned and degreased with gasoline, cut out foreign inclusions with a cable knife and cut off protruding edges and burrs in places where the hose is damaged.

To repair punctures of small holes and shells, the damaged area in the hose or sheath and the end of the filler rod are heated for 10 ... After cooling, making sure that the welding of the rod is strong by lightly twitching it, the rod is cut off. To seal and level the weld, the repair site is heated until signs of melting appear, after which a piece of cable paper folded in 3-4 layers is pressed against the heated area by hand. For reliability, the operation is repeated 3-4 times. To repair a hose that has slots, slots and cutouts, the end of the filler rod is welded to the whole place of the hose at a distance of 1 - 2 mm from the damage site. After making sure that the weld is strong, direct the air stream so that the lower part of the filler rod and both sides of the slot or slot are simultaneously heated. By lightly pressing on the bar, the latter is laid and welded along the slot or slot. The welding of the rod is completed on the whole place at a distance of 1 - 2 mm from the damage. Then, the protruding surfaces of the bar are cut off with a knife and the welded seam is aligned.

Hose or sheath ruptures are repaired with PVC patches or cut cuffs. The patch is made of plastic so that its edges overlap the gap by 1.5 - 2 mm. The patch along the entire perimeter is welded to the hose, and then a filler rod is welded along the formed seam, and the protruding surfaces of the rod are cut off and level the seam at the welding site.

To repair a hose or sheath using a split cuff, a piece of PVC tube is cut off by 35 ...
... 40 mm above the damaged area, cut the tube lengthwise and put it on the cable symmetrically to the damaged area. The cuff is temporarily fixed with a PVC or calico tape with a pitch of 20 ... 25 mm, the end of the bar is welded at the junction of the cuff with the hose (sheath), and then the bar is laid and welded around the end of the cuff. After welding both ends of the cuff to the hose (sheath), the temporary fastening tapes are removed, the rod is welded along the cut of the cuff, the protruding surfaces of the rod are cut off and all welds are finally aligned.

Repair of PVC hoses and cable sheaths can also be carried out using epoxy compound and glass tape. The surface of the hose or sheath is pre-treated as above and roughened with a bastard file. Location of damage
and beyond its edges at a distance of 50 ... 60 mm in both directions, they are lubricated with an epoxy compound with a hardener introduced into it. 4-5 five layers of glass tape are applied over the epoxy compound layer, each of which is also smeared with a compound layer.

Temporary repair of hoses and sheaths in order to prevent the penetration of moisture under the cable sheath, as well as the leakage of bituminous composition from under the hose, is allowed to be carried out using a sticky PVC tape with a 50% overlap in three layers with the top layer being smeared with PVC varnish No. 1. According to the second method, temporary repair is performed with LETSAR tape in three layers with a 50% overlap.

Painting armored tapes. If the cable armor is destroyed by corrosion, it is painted. It is recommended to use heat-resistant pentaphthalic varnishes PF-170 or PF-171 or heat-resistant oil-bitumen paint BT-577. Painting is carried out using a paint sprayer, and in its absence - with a brush.

Armor repair. The sections of destroyed armor tapes found on openly laid cables are cut off and removed.
In places of cut tapes, temporary bandages are performed. Next to the temporary bandages, both tapes are carefully cleaned to a metallic sheen and tinned with POSSu 30-2 solder, after which the ground wire is fixed with bandages made of galvanized wire with a diameter of 1 - 1.4 mm and soldered with the same solder. The cross section of the ground conductor is selected depending on the cross section of the cable cores, but it must be at least 6 mm 2.

When tinning and soldering armored tapes, soldering fat is used. The duration of each soldering should be no more than 3 minutes. Temporary bandages are removed. An anti-corrosion coating is applied to the exposed area of ​​the shell.

In those cases when mechanical impacts on the repaired section of the cable are possible, one layer of armored tape is additionally wound on it along the layer, which is previously dismantled from the cable section with intact armor. The tape is wound with a 50% overlap and secured with bandages made of galvanized wire. In this case, the ground conductor must be fluffed along the entire length of the jumper in order to create a tight fit of the armor around the repaired cable section.

6.3. Repair of metal shells

If, when the cable sheath is damaged (cracks, punctures), a leak of the oil-rosin composition is detected in this area, the sheath is removed from both sides at a distance of 150 mm from the damage site. The top layer of belt insulation is removed and checked for moisture in heated paraffin.

In the event that moisture is absent and the insulation is not destroyed, the lead or aluminum sheath is repaired.

From sheet lead 2 ... 2.5 mm thick, a strip is cut out 70 ... 80 mm wide above the bare section of the cable and 30 ... 40 mm long more than the circumference of the cable along the sheath.
Two filling holes are made in the strip so that they are located above the separated part of the cable. The strip is thoroughly cleaned of dust and dirt with a rag soaked in gasoline.

The removed semi-conductive layer of paper and the upper tape of the belt insulation are restored and secured with bandages made of cotton threads. The site is scalded with MP-1 cable mass.

A strip of lead is wrapped around the exposed area of ​​the cable so that it goes evenly onto the edges of the cable sheath, and the edges of the formed lead pipe overlap each other by at least 15 ... 20 mm. First, the longitudinal seam is soldered with POSSU 30-2 solder, and then the ends of the pipe are bent to the cable sheath and soldered to it.

For cables with an aluminum sheath, at the place where the lead pipe is soldered, the cable sheath is tinned with solder
ki A. The coupling is filled with hot cable mass MP-1. After cooling and topping up, seal the filling holes. On the place soldered at the ends, a bandage of copper wire is applied coil to coil with a diameter of 1 mm with an exit of 10 mm on the cable sheath and soldered to the sheath. The repaired area is covered with resin tape in two layers with a 50% overlap.

In the event that moisture has penetrated under the sheath or the belt insulation is damaged, as well as the core insulation, the cable section is cut out along the entire length where moisture or insulation damage is found. Then insert a piece of cable of the required length and carry out the installation of two couplings. The cross section and voltage of the cable must correspond to the cut section.

The cable brand for insertion may be different, but similar to the cut section.

6.4. Restoration of paper insulation

In cases where it is not the conductive cores that are damaged, but the insulation of the cores and the belt insulation, and there is no moisture in it, the insulation is restored with the subsequent installation of a split lead coupling.

The cable is opened to such a length that it is possible to create sufficient slack in it for breeding the cores among themselves. After dilution of the cores and removal of the old insulation, the insulation of the cores is restored by applying paper rollers or LETSAR tape with pre-treatment with MP-1 scalding mass. A split lead sleeve is installed and the longitudinal seam is first soldered, and then the sleeve is soldered to the cable sheath.

Such repairs can be performed on horizontal sections of cable routes, where there is no increased oil pressure, since the sleeve with longitudinal soldering has a lower mechanical strength.

6.5. Repair of conductive wires

If the rupture of the cable cores occurred at an insignificant length and it can be pulled up due to the “snake” made during laying, the usual repair of the connecting lead or epoxy coupling is carried out. If there is no reserve cable length, you can use extended connector sleeves and couplings. Repair in this case is carried out with one connecting lead coupling. In all other cases, when repairing the conductive cable cores, a cable insert is used and two connecting lead or epoxy couplings are installed.

6.6. Coupling repair

Repair of the coupling or installation of a cable insert and two couplings is carried out after inspection of the coupling and its disassembly.

If the breakdown occurred from the place of soldering of the core or from the sleeve to the body of the lead coupling and the destruction is insignificant and the insulation is not moistened, the coupling and the damaged part of the insulation are sequentially disassembled. Then the insulation is restored with paper rollers or LETSAR tape and scalded with MP-1 mass. A split coupling housing is installed and all further operations for mounting the coupling are performed.

If a breakdown occurs in the neck of the coupling from the core to the edge of the sheath and the insulation is not moistened, the coupling is disassembled, then a section of the armor and sheath is cut off to the length necessary for convenient breeding of the cores. The insulation of the damaged core is restored and scalded. An elongated split body of the lead coupling is installed and all operations for mounting the coupling are performed.

If the damage is significant, then a cable insertion is used with the installation of two couplings according to the technology provided for by the technical documentation.

In most cases, damage to couplings occurs during preventive tests with increased voltage. And if the repair is not started immediately after determining the location of the damage, moisture will begin to flow into the coupling. In this case, the defective sleeve and cable sections are cut out. As a rule, the longer a damaged and unrepaired sleeve is in the ground, the longer the cable insertion will be when repairing the cable line.

6.7. Repair of outdoor terminations

Outdoor terminations generally fail during rainy periods of the year or high relative humidity. The damaged sleeve must be cut off, the cable insulation must be checked for moisture and, if the paper insulation is not moistened, the sleeve must be installed in accordance with the requirements of the technical documentation. If the length of the cable at the end of the line has sufficient margin, then the repair is limited to the installation of only the termination. If the supply of the cable is not enough, then at the end of the cable line, insert the cable of the required length. In this case, it is necessary to mount the connecting and end sleeves.

In outdoor terminations with a metal case, once a year during the entire operation period, the seals are checked and the nuts are tightened. At the same time, the contact connections are inspected and, if necessary, the contact surfaces are cleaned and the bolts are tightened.

Soldering points, reinforcement seams and seals are systematically painted with enamel. The surface of outdoor epoxy end sleeves must be painted with air-drying enamels during operation (once every 3…5 years, depending on local conditions). Painting is carried out in dry weather, having previously cleaned the surface of the coupling and insulators.

The insulators of the terminations of outdoor and indoor installations, as well as the insulating surfaces of the terminations, must be periodically cleaned of dust and dirt with a lint-free cloth soaked in gasoline. More frequent cleaning should be carried out on cable terminations in industrial workshops and areas with conductive dust. The frequency of wiping and cleaning the end cable fittings at this electrical installation is established by the chief engineer of the local power company.

6.8. End termination repair

In case of destruction of the body of the seal and burnout of the cores in the spine, they are repaired in the same way as the end couplings. In this case, the termination body and parts cannot be reused.

Repair of terminations in steel funnels in case of destruction of the insulation of the cores is carried out in the following sequence: the destroyed or worn out insulation of the cores (contamination, moisture) is removed, one layer of paper insulation is wound up, winding up in five layers with a 50% overlap with adhesive PVC tape or three layers of rubberized tape, followed by coating with insulating tapes or paints. Repairs can also be made using LETSAR tapes (two layers) and PVC (one layer). In case of cracking, flaking, partial maintenance and significant contamination of the casting composition, especially when these defects are accompanied by a noticeable displacement of the strands between themselves or to the funnel body (which in turn can be caused by an incorrect position or absence of a spacer plate), the steel funnel should be completely refilled.

The old casting composition is removed (melted out), the funnel is lowered down and cleaned of soot and dirt. After winding a new seal (under the funnel), the funnel is put in place.

The mouth of the funnel is wrapped with resin tape, then the funnel, together with the cable, is attached to the supporting structure with a clamp. Check the correct position of the porcelain bushings, and then use the potting compound.

Repair of terminations made of PVC tapes is carried out when the impregnating composition gets into the spine or on the cores, when the tapes crack and break. Carry out dismantling of old tapes and reeling on the conductors of new PVC or LETSAR tapes.

Repair of epoxy terminations in case of destruction of the windings on the cores is carried out with the dismantling of old tapes, the restoration of new LETSAR tapes and additional grouting of the epoxy compound so that the tapes go into the poured compound by at least 15 mm.

In the event of leakage of the impregnating composition through the cable in the root of the termination, the lower part of the termination is degreased in section 40 ...
... 50 mm and at the same distance a section of armor or sheath (for unarmored cables). On the fat-free section of the termination body and the cable section adjacent to it with a width of
15 ... 20 mm, a two-layer winding is applied from a cotton tape lubricated with an epoxy compound. The repair mold is poured (Fig. 6.3) with an epoxy compound.

In case of leakage at the exit point of the cores from the body of the termination, the upper flat part of the body of the termination and the sections of tubes or winding of the cores 30 mm long adjacent to the body are degreased. A removable repair form is installed (Fig. 6.4), the dimensions of which are selected depending on the standard size of the seal. The mold is filled with compound. In case of leakage on the cores, the defective section of the tube or core winding is degreased and a repair two-layer winding of cotton tapes is applied with abundant epoxy coating of each turn of the winding or LETSAR tape in three layers.

If the tightness is broken at the junction of the tube or winding to the cylindrical part of the tip, the surface of the bandage and the section of the tube or winding of the core 30 mm long are degreased. A two-layer winding of cotton tapes is applied to the fat-free areas with abundant coating of each turn of the winding with a compound. A tight bandage of twisted twine is applied over the winding and coated with an epoxy compound.

6.9. Repair of cable lines 0.38 ... 10 kV

When a cable line is taken out for repair, the nature and location of the damage should be determined. Depending on the nature of the damage, either protective covers are repaired, or paper insulation and conductive wires are repaired with the installation of connecting and end sleeves, followed by phasing and high voltage testing.

To repair dry patches, remove discolored or cracked tapes, check the paper insulation for moisture, and apply new tapes, reinforcing them with bandages. Recommendations for the use of methods for terminating, connecting and branching aluminum cores of cables up to 10 kV are given in Table. 6.1, and copper conductors - in table. 6.2.

The designs of connecting sleeves and tips are shown in fig. 6.5.

Rice. 6.5. Connecting sleeves and tips:

A- copper tip type P; b - copper connection sleeve

for soldering; V- copper tip fixed by crimping;

G - crimped copper sleeve

Various industrial presses are widely used for connecting and terminating copper and aluminum conductors. For crimping, select the appropriate tips or sleeves, punches and dies. From the ends of the cores, the insulation is removed for the length of the cylindrical part of the tip or for half the length of the sleeve. Sector single-wire conductors are rounded using presses or rounding pliers, stranded conductors - using pliers. For aluminum conductors, aluminum tubular sleeves and tubular aluminum lugs of the TA or TAM type (copper contact part) are used. The inside of the tips and sleeves are wiped, cleaned and lubricated with quartz paste. The cores are also prepared, after which tips or sleeves are put on them. Crimping for tips is performed in one step with a two-toothed tool, in two steps - with a single-toothed tool; the sleeve is pressed in two steps with a two-pronged tool and in four steps with a single-toothed tool.

The termination of aluminum single-wire conductors is also performed using pyrotechnic presses PPO-95 and
PPO-240; punches and dies are selected according to the sections of the cores. The insulation from the cores is removed over a length of 45 mm for cables with a cross section of 25 mm 2; 50 mm for 35…95 mm 2 ; 55 mm for 120…240 mm 2 .

For crimping copper conductors, copper sleeves and copper tubular lugs are used. The cores, sleeves and tips are cleaned. On the cores, the tips are pressed with one indentation, and the sleeve with one on each side.

The most common methods for connecting and terminating the cores of cables up to 10 kV are soldering and crimping, that is, methods that can be used both in the repair of cable lines and in the switchgear.

The cores are connected to each other and the core to the tip using molten solder. Stranded conductors are crimped with universal pliers to facilitate putting on tips, sleeves or steel forms. Single-wire cores are rounded using presses or special crimping pliers. From the ends of the cores, the insulation is removed along the length of half of the sleeve or steel mold plus 10 mm.

Copper conductors are soldered in tinned copper sleeves with tin-lead solders using fluxes by fusing the solder directly or by pouring molten solder into the sleeves. When solder is fused with a burner flame, the sleeve is heated with tinned copper wires inserted into it and richly lubricated with flux, then the solder stick is inserted into the burner flame and the sleeve is filled with molten solder.

Table 6.1

Scope of termination and connection methods

aluminum conductors of cables up to 10 kV

Type of work, method of execution	Cross-section of conductors, mm 2
ending
Crimping with tubular lugs TA and TAM and pin lugs ShP		Should apply
Stamping of a tip from a single-wire core with a powder press
Soldering tips R		Should apply
Propane-oxygen welding with ADZ-1T1 alloy plates
Electric arc welding in shielding gas with shas tips		Allowed
Compound
		6-10 kV

The end of the table. 6.1

In the second method, a steel ladle with solder in the amount of 8 ... 10 kg is heated to a temperature of 245 ... 270º C and placed under the soldering point. With a metal spoon, solder from the ladle is poured several times into the sleeves, thereby heating them to the temperature of the solder.

Table 6.2

Scope of methods for terminating and connecting copper conductors of cables up to 10 kV | 13]

Type of work, method fulfillment	Cross-section of conductors, mm 2
ending
Crimping with tubular lugs		Should apply
Soldering tips R
Soldering a stranded core with the formation of a monolith with a plug-in tip		Allowed
Compound
Crimping with tubular sleeves		Should apply
Sleeve soldering

Note. Recommendations for use mean (in accordance with the PUE): should apply- this requirement prevails; recommended- this decision is one of the best, but not mandatory; allowed- this decision is applied as an exception, as a forced one.

Aluminum conductors are soldered together with zinc-tin or tin-copper-zinc solder. The cores before soldering are prepared either by stepwise cutting into layers for connection in sleeves, or in steel forms with a core cut at an angle of 55º. Single-wire conductors are prepared only with a cut at an angle of 55º (Fig. 6.6).

Step cutting of cores by layers (Fig. 6.6) is carried out subject to the following conditions:

Conductor cross section, mm 2 16…35 50…95 120…240

Number of steps 1 2 3

The length of the core section, cleaned

insulation, mm 2 ... 50 60 70

Fig.6.6. Preparation of aluminum stranded conductors for soldering:

A- stepped cutting of veins by layers; b - cutting the core at an angle;

V- a template for the design of the ends of the cores; 1- lived; 2 - sample;

3 - core cutting line

For connection in sleeves or in steel detachable forms, the ends of the cores are serviced with grade “A” solder by rubbing, and then tin-lead (Fig. 6.7). The edges of the insulation are wrapped with asbestos cord to protect it from charring. Before soldering, it is recommended to install protective screens and wind up the asbestos cord. Soldering is performed by fusing solder into a sleeve or mold, heating them with a burner flame. Solder is mixed with a steel stirrer and slags are removed.

Rice. 6.7. Soldering the core with solder:

1 - aluminum stranded conductor with stepped cutting;

2 - insulation; 3 - solder stick; 4 - metal brush; 5 - burner

Soldering by pouring preheated solder in cast-iron crucibles is carried out in steel detachable molds. The crucible with molten solder TsO-12 is located near the soldering. A tray made of steel is attached to the cores and lowered to the edge of the crucible, so that as a result of watering with a metal spoon, the solder merges into the crucible after heating the steel mold. As a result, the cores are heated to a temperature of 500 ... 550 ° C and soften (Fig. 6.8).

Rice. 6.8. Connection of soldering cores by pouring molten solder:

1 - soldering spoon; 2 - form; 3 - tray; 4 - crucible; 5 - scraper

Simultaneously with the softening of the ends of the veins cut at an angle of 55 °, an oxide film is removed from them with a scraper. The crucible with the amount of solder 7 ... 8 kg is heated before soldering each core, as it cools quickly. When the amount of solder in the crucible is up to 15 ... 18 kg, heating is performed 1 time. Aluminum conductors with a cut at an angle of 55 ° are placed in molds at a distance of 2 mm from each other to remove the oxide film from the entire surface of the oblique cut, thereby increasing the soldering area and improving its quality.

To connect aluminum conductors with copper, either tinned copper sleeves or steel detachable forms are used. Aluminum conductors are pre-tinned with grade “A” solder, and then with tin-lead. Soldering is performed with the same solder. When soldering with TsO-12 solder in steel molds, the copper core is pre-tinned with tin-lead solder, the aluminum core is cut at an angle of 55 ° (Fig. 6.6).

For the termination of copper and aluminum conductors, copper tinned lugs of type P are used. Multi-wire sector conductors are rounded off with universal pliers, and single-wire ones - with a press or rounding pliers. A tip is put on the copper wires, sealed with an asbestos cord, a flux is introduced and the tip is heated with a burner flame. Then tin-lead solder is injected into the heated tip. Solder, melting, fills all the spaces between the wires of the core and the tip.

Stranded aluminum conductors before soldering are tinned with grade A rubbing solder, then with tin-lead. Aluminum conductors are soldered in the same way as copper conductors. The second method is used in the main for soldering single-wire cores. The ends of the cores are cut at an angle of 55, the tip is put on the core, the bottom is sealed with an asbestos cord to protect the paper insulation from charring and from leakage of solder during soldering. Soldering is done with solder
CO-12 without the use of flux. The tip is heated with a burner flame and a solder stick is introduced into it; molten solder fills the voids between the wires and the tip; under a layer of molten solder, a scraper removes an oxide film, which passes into slag.

The method of cutting a cable with paper insulation for mounting lead sleeves is shown in fig. 6.9.

Rice. 6.9. Cutting paper-insulated cable for mounting

lead couplings:

1 - outer cover; 2- armor; 3- shell;

4 - belt isolation; 5 - core insulation; 6 - cable core;

7, 8 - wire bandages

Cable cutting for installation of cast-iron couplings is shown in fig. 6.10.

Modern use of electricity requires increased reliability of power supply. Therefore, an important point is the high operational quality of cable lines. The reliability of cable lines largely depends on the quality of connections, installation and cable laying. This indicator is provided by modern heat-shrinkable cable sleeves. They are used in the installation and repair of cable lines, the repair of already laid ones, the installation of branch and terminal (terminal) terminations. For each type of electrical work and cable types, specialized cable couplings are produced: coupling (linear), branch, transition and termination.

Operation of cable lines and repair of cable lines.

During the entire life of the cable line (CL), various damages can occur on it. Caused by mechanical damage (gusts, breakdowns), time and loads on this line. To eliminate which requires qualified repair work (cable repair). Current repair work is also periodically performed, these are: defects in corrosion and oxidation of its sheath, inspect cable channels, inspect cable terminations, check markings, determine the cable heating temperature under load (pyrometer), check the heating and contact of the tips. Also, grounding check, elimination of identified defects, access to cable wells, if necessary, some sections of the cable line are re-routed, installation of couplings and terminations.

Installation of couplings and terminations not as easy to produce as some may have thought. Incorrect installation of the sleeve on the cable can lead to very unpleasant consequences, including unnecessary financial costs. Here it is necessary to take into account many factors of a technical and natural nature, all the conditions for the upcoming electrical installation operations. The same applies to such a complex matter as the repair of power cables. To do all this at a decent level is only possible for a master of his craft. A cable splicer is a rather rare technical specialty, however, by contacting us, you will definitely find such a person.

1. The order of work performed during the repair of power electric cables 0.4-6-10 KiloVolt with visible damage.

If the cable line has been mechanically damaged, with a visible break or damage. (Puncture, rush, cut, etc.).

1. Make sure that there is no voltage on the damaged cable. Disconnected in the substation or switchboards.

Cable rupture and short circuit short circuit, on the cable, even if it is completely broken, does not give a full guarantee that the cable was left without voltage. From experience: PVC-insulated cables up to 1 kV, and 6-10 kV lead-sheathed cables, when completely broken, can remain under full or partial voltage. Since the cable cores break earlier than the cable insulation. In this case, no short circuit occurs, and the protective equipment is not turned off.

2. Excavation of the damaged cable. Excavation.

For repair work on the cable (for installing couplings or two couplings with an insert), it is necessary to provide a free, straight, excavated area, 1.5-2 meters in size at both ends from cable damage and 0.6-0.7 meters wide - when installing one coupling. When installing two couplings with an insert, it is necessary to make a pit, together with the proposed cable connection in the amount of 1.5 meters by 0.7 meters. It is also necessary to take measures to prevent the ingress of moisture instead of a cut or a break in the cable.

3. Installation and installation of cable boxes. Cabling.

After the cable was disconnected and dug out. Check cable insulation for moisture. Installation of cable boxes.

4. Test the cable with increased voltage.

For cables up to 1000 V, the insulation test is carried out with a megohmmeter.

For cable 6-10 kV. insulation test is carried out (kenotron), in 5-6 times the nominal working voltage of the cable.

5. Backfilling of the cable line.

When backfilling the cable, it is necessary to provide a (pillow) of sand without stones. 10 cm below, and 10-15 cm above the cable. Laying with signal tape is carried out on top. And the final filling.

Installation of cable glands

In cable routes, joints are the most vulnerable point, so the requirements for them are no lower than for the cable itself. The connection of the cores is carried out by welding, soldering, crimping or bolting. Cable sleeves are used to restore the screen, insulation and armor.

In addition to the actual insulation and protection of the spliced ​​route, the installation of cable sleeves solves two problems that arise when splicing a cable.

When docking the cable, a section of the screen is removed. If you do not restore it, the electrical characteristics of the route are violated. The unevenness of the electric field strength causes the concentration and localization of field lines, the resulting ionization leads to breakdown and failure of the entire cable line. The second problem is the appearance of the tracking phenomenon at the joints. Pollution of the atmosphere and industrial premises leads to the deposition of dirt on the insulation and the formation of conductive paths. The consequences are the same - breakdown of the junction and failure of the line.

According to their purpose, cable joints are divided into:

Connecting (serve to connect pieces of the cable route);

Branch lines (for connecting the cable line to the trunk);

Terminal (for connecting electrical installations).

End mast couplings are required for connection to overhead power lines.

Cable joints are:

lead,

From epoxy mixtures,

Shrink

Cold shrink

The coupling must provide resistance to the environment, mechanical and electrical strength, be sealed and moisture resistant. These requirements are best met by hot and cold shrink sleeves used to connect cables with any insulation. Their use allows you to reduce labor and time costs, to carry out work in tight spaces. These apparently similar couplings differ in physical properties, installation methods and applications.

Heat-shrinkable sleeves can be used for any method of laying cable lines, they have a long service life - more than 30 years, and are easy to install. One standard size of a heat-shrinkable sleeve can be used for different cross-sections of cores and types of cables, their fittings are practically not subject to aging and can be stored for an unlimited time. Heat shrink sleeves are highly rigid, resistant to most aggressive environments, but require UV protection.

Cold shrink sleeves have all the advantages of heat shrinkable sleeves, but do not require heating during installation, this reduces the installation time of the sleeve by approximately 2 times. In cold shrinking, silicone or EPDM rubber is used as the insulating material. Silicone is UV resistant, water repellent, but not very abrasion resistant. EPDM rubber cable glands are more durable but require additional UV protection.

At the junction, heat-shrinkable and cold-shrinkable sleeves retain the flexibility of the cable, they are resistant to cyclic temperature changes and seasonal soil displacements, their tensile strength under tensile force is 60% of the tensile strength of the cable itself. When working on cable lines, it is optimal to combine both technologies.

Installation of a heat-shrinkable cable sleeve Before mounting the sleeve, the end of the cable is cut: all its layers are removed sequentially with some shift, starting from the outer protective coating to the phase insulation of each core. The dimensions of the cut are strictly regulated, depend on the cross-section and brand of cable cores, line voltage, and are given in reference books and installation instructions.

The heat shrink sleeve kit includes: tubes, cuffs, hoses, gloves and other items supplied in a stretched state. During installation, they are easily put on the elements of the cut cable. Heating with a building hair dryer or burner leads to shrinkage of the parts, they tightly cover the cable elements and provide mechanical strength to the structure. Shrinkage temperature - 120-150°C, it is not dangerous for insulation. When heated, the sealants applied to the inner surfaces of the coupling parts melt, fill the voids and ensure the sealing of the joint. Sealants contain special additives that equalize the electric field at the point of contact. This protects the connection from breakdown.

a - cut cable; b - shrinkage of the tube that equalizes the electric field; c - shrinkage of the core cuff; d - connection of the ground conductor and shrinkage of the hose; e - shrinkage of the end cuff; e - shrinkage of the waist cuff.

Installation of a three-core cable is carried out in the same way, but heat-shrinkable gloves are used instead of heat-shrinkable tubes. They are put on 3-phase cores of a pre-cut cable.

Installation of a cold-shrinkable cable gland

A cold-shrinkable sleeve is a pre-stretched product mounted on a spiral plastic cord. As the helix is ​​pulled out, the sleeve fits snugly around the cable, providing a complete seal. The thick walls of the coupling reliably protect against mechanical influences.

In order to connect or terminate the cable, cable sleeves and special cuts are used. Electricians who perform this type of work must be highly qualified and take special courses. In addition, each employee who installs the cable sleeve must have a certificate of the appropriate form, which must be renewed every three years, after passing the briefing and passing the exams.

After connecting the power conductors, it is necessary to check the junction, the contact resistance in this section should not be higher than the resistance of the entire section, and the dielectric strength of the insulation should not be worse than in the rest of the cable section.

After the coupling has been installed, this place must be reliably protected from moisture and mechanical damage. Cable sleeves up to 1 kV, which are laid in the ground, are made of cast iron, and they are filled with bituminous resin or fiberglass.

Cables rated for voltages up to 10 kV are connected using epoxy couplings. The body and spacers of such couplings are manufactured in factories. If it is necessary to install couplings, or termination voltages up to 1 kV, then it is possible to mount couplings without a factory case - in this case, the compound is poured into removable molds made of metal or plastic.

20 and 35 kV cable sleeves are single-phase with a brass body.

Plastic insulated cables can be joined using epoxy sleeves, which are similar to oil-paper cable sleeves.

When mounting terminations, close attention must be paid to sealing the insulation. It is also necessary to protect the cable from mechanical damage and bring the cable cores out. Cable terminations are mainly used in outdoor installations. Indoors, it is allowed to terminate the cable using funnels and dry terminations made of PVC tapes, as well as lead and rubber gloves.

Dry funnels are used when installing cables up to 10 kV with paper-oil insulation. If it is necessary to install a cable sleeve with a voltage of more than 1 kV, then the funnels that are used to connect the cable must have porcelain bushings.

If the room is guaranteed complete protection from precipitation, sunlight and dust, then the use of cable glands using epoxy compound is allowed. This method is recommended for use in electrical installations up to 10 kV.

In internal electrical installations up to 10 kV, it is allowed to work with lead gloves, and in installations up to 6 kV, it is also possible to use rubber gloves.

Lead gloves are much stronger and more durable, but they are very expensive to manufacture and difficult to assemble. It is very convenient to use lead gloves in case of bottom termination of cable ends of different levels. The use of rubber gloves is not allowed if the level difference is more than 10m.

Polyvinyl chloride tape dry terminations are often used in cases where it is necessary to install cable glands on horizontal sections of the cable at the top point, which has different levels of ends. The use of this material is allowed in rooms with a maximum temperature of up to 400˚С. Such seals are by far the most optimal choice - they are resistant to chemical attack, easy to operate and cheap to manufacture.

Metal cable glands for external installation, installed on cables with a voltage of about 10 kV, have inclined or vertical terminals. The body of such couplings is cast iron or aluminum alloy, to the body of which porcelain insulators are attached. The rods of these insulators inside the sleeve are connected to the lugs of the cable cores.

Very often, the installation of couplings allows the use of heat-shrinkable materials. The use of "thermal shrinkage" helps prevent moisture and dirt from entering the surfaces to be joined, as this may adversely affect such a connection in the future.

Such materials are becoming more and more popular, and they are obtained from conventional thermoplastics by chemical, radiation, or other processing. The main advantage of heat-shrinkable materials is the so-called "shape memory". This is the ability of products that were previously stretched in a heated state and then cooled to ambient temperature to maintain their shape indefinitely. After heating to 120-150 degrees, heat-shrinkable materials return to the shape that was before the initial processing. Also, the indisputable advantage of such materials is that they can be used to easily install the coupling, and the price of the material is relatively low.

Due to this property of the material, it becomes possible not to limit the installation tolerances, due to this, installation and assembly work is simplified, and their labor intensity is reduced, while the cost of such work, due to the use of relatively inexpensive materials, is falling every day.

Types of damage to cable lines

Enterprises that have allowed such situations may incur repair costs, leading to financial losses. Diagnostics of pipelines and power cable lines, determination of the places of their damage requires serious instrumentation.

Let's start with the fact that all today's known traverse detectors, both domestic and foreign, operate on the same principle - electromagnetic induction. All of them react to the electric current flowing through the communication. There is a current - we work in a passive mode (without a generator), there is no current - we create it using a generator. Thus, we can come to the conclusion that it is possible to work with any route finder and achieve equal results. However, in practice, everything turns out to be much more complicated, and the slightest advantages of the device make it possible to more effectively solve practical problems.

As a rule, locators have a highly selective heterodyne receiver, which provides high noise immunity and sensitivity, makes it possible to work in conditions of strong external interference, with a weak signal level (communication detection depth - up to 6 meters) and increases the chances of success in areas saturated with communications. At all,
the last problem is of great importance now, because sometimes something unimaginable happens in the ground: decades of communication fit into the ground, and there are no schemes, and now, when the need arises, it is very difficult to dig without hurting someone's "interests".

Untangling such tangles is a great art. It is most convenient to do this “by ear”, relying on the tone of the receiver signal. A true professional can confidently distinguish a network pipeline from a gas pipeline, and it is not difficult to distinguish a power cable from a pipeline. It is this "hearing" advantage, when you can go along the "own" line by the tone of the sound signal, while excluding "strangers", we lose when using locators with microprocessor signal processing.

The use of 2-3 operating frequencies of the generator for "active" cable tracing, as well as the presence of an inductive antenna, allow you to determine the location of the cable without a direct connection to the communication.

Let us dwell in more detail on the method of finding the place of damage to the power (electric) cable. In the event of a power cable malfunction (break, short circuit, insulation breakdown), as a rule, RZ and A are triggered, and the cable is disconnected from the power supply network. To find out the cause of the malfunction, it is necessary to analyze the cause of the shutdown (by what protection: overcurrent, TO, OKZ, etc.), and the type of damage. The choice of method for determining the location of a cable fault depends on the nature of the fault and the contact resistance at the fault location.

Damage types:

single-phase short circuit to "Earth"; - interfacial short circuit;

two, three-phase short circuit to "Earth";

breakage of cable cores without grounding or with grounding of both broken and unbroken cores;

floating breakdown, manifested as a short circuit (breakdown) at high voltage and disappearing (floating) at rated voltage.

The main methods for determining the damage zone:

loop method.

Overlay frame method.

Method of oscillatory discharge.

capacitive method.

impulse method.

induction method.

acoustic method.

The sequence (algorithm) of the search for the damage site:

To search for a cable damage point, it is necessary to prepare a workplace: disconnect and disconnect the cable from both sides; verify from the diagram that there are no transit branches. After performing organizational and technical measures, in many cases, in order to determine the location of cable damage, it is necessary that the resistance at the location of damage between the core and the sheath be as small as possible. The reduction of this transient resistance to the required value is carried out by burning the insulation with special installations. The burning process proceeds differently, depending on the nature of the damage and the condition of the cable. Usually, after 15-20 seconds, the resistance drops to several tens of ohms. With moistened insulation, the process takes longer, and the resistance can only be reduced to 2-3 kOhm. The process of burning in the couplings takes a long time, sometimes several hours, and the resistance changes sharply, then decreasing, then increasing again, until the process is established and the resistance begins to decrease.

In case of damage to the cable lines, the damage zone is preliminarily determined (relative methods), and after that, by various methods (absolute or cartographic), the location of the damage is specified on the route directly. For a more accurate determination of the damage zone, it is desirable to perform measurements from one end of the cable by several methods, if this is not possible, a more accurate result is obtained by measuring by one method from both ends of the cable.

Measure the insulation resistance (Riz) between the phases and between the phases and "Earth" and analyze the condition of the cable insulation resistance. According to the state of the cable insulation resistance, it is possible to draw a conclusion about the type of damage (megger).

If the damage is a single-phase short circuit or the transition resistance is large, then the cable must be “burned”. For this, installations for burning (afterburning) cables of the type: UP-7; APK-14; MPU-3 "Phoenix", "Skat-70", etc.

By connecting a reflectometer (R-5-10; R-5-13 or another) to the cable cores, view the phase diagrams and determine the preliminary distance to the fault.

After a preliminary determination of the location of the cable damage, the search for the exact location of the damage is carried out by induction or acoustic methods.

Search for the place of damage by the induction method.

This method is used to directly search for damage points on the cable route during a breakdown of the insulation of the cores between each other or to the “ground”, a break with a simultaneous breakdown of the insulation between the cores or to the “ground”, to determine the route of the cable and its depth, to determine the location of the couplings .

The essence of the method lies in fixing from the earth's surface with the help of a receiving frame the nature of the change in the electromagnetic field above the cable when an audio frequency current (800-1200 Hz) is passed through it from fractions of an ampere to 20 A, depending on the presence of interference and the depth of the cable. The EMF induced in the frame depends on the current distribution in the cable and the mutual spatial arrangement of the frame and cable. Knowing the nature of the change in the field, it is possible, with the appropriate orientation of the frame, to determine the route and the location of the cable damage. More accurate results are obtained when current passes through the “core-core” circuit, for which single-phase short circuits are “burned out” to two or three-phase ones or an artificial “core-cable sheath” circuit is created, grounding the latter on both sides.

The power lines of the current field "vein-earth" are concentric circles, the center of which is the axis of the cable (after a single current). When using the circuit "core-core current. going along the forward and reverse wires, creates two concentric magnetic fields acting in opposite directions (the field of a pair of currents). When the cores are located in a horizontal plane, the resulting field on the earth's surface is the largest, and when the cores are located in a vertical plane, it is the smallest. Since the cables have twisted cores, an EMF will be induced in a frame located vertically and moving along the cable route, varying from minimum to maximum.

When looking for damage, it must be remembered that the signal behind the damage site attenuates at a distance of no more than half a step.

We connect the generator to the cable cores according to the accepted scheme (depending on the type of damage). We coordinate the load. Using an electromagnetic sensor (EMD), a receiving unit (PB) and headphones (GT), we are looking for a place where the cable line is damaged. At the point of damage, the signal from the generator sharply increases, and then fades.

Finding the damage site by the acoustic method.

The essence of the acoustic method is to create a spark discharge at the site of damage and listen on the track for the sound vibrations caused by this discharge that occur above the site of damage. This method is used to detect all types of damage, with the condition that an electrical discharge can be created at the damage site. For a stable spark discharge, it is necessary that the value of the transient resistance at the fault site exceeds 40 ohms.

The audibility of sound from the surface of the earth depends on the depth of the cable, the density of the soil, the type of cable damage and the power of the discharge pulse. The listening depth can vary from 1 to 5 meters.

As a pulse generator, for example, generators of the AG-120 tracing type (power up to 180 W) can be used. As a receiver of an acoustic signal, sensors of a piezo or electromagnetic system are used, which convert mechanical vibrations of the ground into electrical signals input to the amplifier. Above the damage site, the signal level is maximum.

We turn on the generator connected to the cable cores and with the help of an acoustic sensor (BP), PB and GT we listen to the cable line in the alleged place of damage. At the point of cable damage, characteristic "clicks" with a given frequency will be heard.

It must be remembered that the latest Russian developments allow the operator to work simultaneously with two sensors: electromagnetic and acoustic. Thus, it is possible to simultaneously trace the cable line and search for the fault location by induction and acoustic methods.

Repair of power cable and installation of cable sleeves

Repair of a power cable with the installation of a coupling

There are quite a few reasons why cables, splices, and terminations can fail. These are: various mechanical damages, installation defects, soil settlement, corrosion of the metal sheath of the cable, factory defects, insulation aging and others. According to the requirements of the relevant documents, all cable lines must be repaired (current or major).

Repair of power cable 0.4-6-10 kV

The current repair of the cable can be:

Urgent - repair of the power cable and installation of cable boxes or other types of work that are carried out in case of deprivation of automatic backup power to receivers of category I or especially important category II, while receivers of all categories are overloaded or limit consumers. Urgent repair of cable lines 0.4 kV or 10 kV is carried out by the repair team during the working day. The basis for its implementation is the instruction of the management of the energy service.

Emergency - repair of cable lines 10 kV or 4 kV when the cable line is disconnected and the voltage is cut off for consumers of all categories without the possibility of supplying it through a high or low voltage cable or temporary hose cables. The need for emergency repairs also arises when the reserve line is heavily overloaded and consumer restriction is required. Emergency repair of the cable is carried out immediately and continues until the cable line is put into operation.

Scheduled - repair of 0.4 kV cable lines, as well as any repair of 10 kV cable lines, in cases that are not indicated above, carried out according to a pre-drawn plan approved by the management of the energy services. This schedule is compiled on a monthly basis, taking into account the records available in the inspection and detour logs, the results of measurements and tests, and information from dispatch services.

When repairing a cable, it becomes necessary to carry out such a type of work as the installation of cable sleeves. What is it and what is it used for?

Installation of cable boxes: connecting and end

A cable sleeve is a device used to make connections, branch cables, as well as to connect them to various electrical equipment and power lines.

The installation of an end sleeve is required when connecting the cable to overhead power lines or to outdoor and indoor devices.

The installation of couplings is necessary when connecting two cables.

The cable sleeve is mounted after preliminary cutting of the factory insulation at the ends of the cables. At the same time, the outer jute cover, armor, a pillow made of paper or fiber, which is under the armor, insulation (general and each core) are removed. Installing cable glands for paper-insulated cables requires a moisture test. If moisture is detected, then a section of the cable is cut out, replaced with a new one, and the sleeve is installed on the cable.

Couplings can be damaged due to high voltage tests or wear out during long-term operation. Repair and installation of the coupling must be carried out in a timely manner, as practice shows that when a damaged coupling is left for a long time, it is necessary to cut out large pieces of cable and make inserts longer for restoration.

Locating a Cable Fault

Cable damage

As a result of the deterioration of the general condition of the cable line (wear, damage to insulation, violation of manufacturing and installation technologies), there is a high probability of a short circuit “to ground” of the phase or a short circuit of the interphase. In case of emergencies, it is necessary to search for a cable break. The choice of the method by which the cable fault location is determined directly depends on the nature of the existing damage and the resistance (transient) in the damaged location. In addition, it also depends on the conditions where the cable is located - you need to search for the cable in the ground or in an open area. A megaohmmeter is used to determine the nature of cable damage.

Methods for determining the location of damage to the power cable

The search for the cable route and existing damage to cable lines is performed by the following methods:

impulse;

capacitive;

oscillatory discharge;

acoustic;

induction.

Cable Fault Location

The pulse method is used when searching for a break in the power cable for any type of damage, except for a floating breakdown, while the transition resistance is not more than 150 ohms. Finding cable damage by the impulsive method is based on measuring the time interval between the moments of the supply of an alternating current pulse and the receipt of a pulse reflected from the fault site. Considering that the speed with which pulses propagate in the low and high voltage lines is a constant value and is 160m/µs, by setting the pulse travel time to the damaged place and back, you can set the distance to the damaged area.

The capacitive method makes it possible to search for a cable fault location based on the measurement of the capacitance of the core, which is cut off using a current bridge (AC or DC).

The oscillatory discharge method is used when it is necessary to search for damage to the power cable during a floating breakdown. The measurement is carried out when voltage is applied to the damaged core from the kenotron test facility, which is smoothly increased to the breakdown voltage. During a breakdown, a discharge occurs in the cable, which has an oscillatory character. The distance to the damaged area is determined by the oscillation period, the propagation of an electromagnetic wave in the cable occurs at a constant speed. For measurements, a REIS-105R reflectometer is used.

Cable burner

The essence of the acoustic method, which is used to search for hidden communications and places of their damage, is to create a spark discharge at the point of damage with listening to the sound vibrations that this discharge caused, which arose above the point of damage. This method is used to search for a short circuit in the cable for any type of damage, if the following condition is met: the possibility of creating an electric discharge in the damaged area. A stable spark discharge is created when the transient resistance exceeds 40 ohms in the damaged area.

The determination of the location of a short circuit by the induction method is used quite widely and provides high accuracy of the results. This method is based on capturing a magnetic field when passing a high-frequency current through the cable. The method is used in those cases when at the point of damage it is possible to form an electrical connection of the conductors (one or two) with a low transient resistance.

Laying power cable in the ground

Cable lines are laid in earthen trenches, special cable structures (cable channels, trays), on overpasses, in galleries, openly along the walls of buildings and structures, in pipes, tunnels, etc. The cheapest way to lay cables is to place the cables in a trench in the ground.

This method does not require large construction costs, and in addition, good conditions are created for cooling the cables. The disadvantages of this method can be attributed to the possibility of mechanical damage to cables during earthworks near the cable route. Cables are laid in trenches at a depth of 0.7 m. No more than 6 cables for a voltage of 6-10 kV or two cables for 35 kV are placed in one trench. It is allowed to lay no more than one bundle of control cables next to them.

The width of the trench along the bottom for one cable is determined by the convenience of earthworks and is 0.2 m at voltages up to 10 kV and 0.3 m at 35 kV. The width of the trench at the top depends on its depth and the angle of repose of the soil.

1 - communication cable; 2 - brick for protection against mechanical damage; 3 - soft soil for backfilling (sand); 4 - cables up to 35 kV; 5 - cables up to 10 kV; 6 - control cables.

In the territories of energy-intensive industrial enterprises and in the presence of more than 20 cables running in one direction, laying in tunnels is used.

In areas with soil conditions that are harmful to cables, in permafrost areas, cables are laid on flyovers and galleries.

Cables are laid openly along the walls of buildings and structures in cases where the building structures are made of fireproof material.

Cable channels are made of prefabricated reinforced concrete tray elements of various widths and heights.

Technology of installation of cable lines

Cable lines are laid in such a way as to exclude the possibility of dangerous mechanical stresses and damage during operation.

Cables are laid with a small margin in case of possible soil displacements and temperature deformations of the cable itself. In trenches and on solid surfaces inside buildings and structures, the reserve is created due to the wave-like laying of the cable, and for cable structures, the reserve is carried out due to the sag. Creation of a reserve of a cable at the expense of rings is not allowed.

Cables laid horizontally on structures, walls, etc. firmly fixed at the end points, at the end sleeves, and at the turns of the route, on both sides of the bends and at the couplings. In vertical sections, the cables are fixed on each cable structure. In the place of rigid fastening of unarmored cables on structures, gaskets made of sheet rubber or sheet polyvinyl chloride or other elastic material are used.

Indoors and outdoors in places accessible to unqualified personnel, as well as where the movement of vehicles, goods and mechanisms is possible, cables are protected by laying them at a height of at least 2 m from the floor or at a depth of 0.3 m in the ground.

Installation of cable lines is carried out in two stages. At the first stage, supporting structures for laying cables are installed inside buildings and structures. At the second stage, cables are laid and connected to the terminals of electrical equipment.

The cable is delivered to the place of installation in its original packaging (reels). Transportation of cables is carried out on conveyors TKB-6, TKB-10 with a carrying capacity of 6 and 10 tons. The TKB-6 conveyor is moved by car, and TKB-10 - by a tractor.

After removing the outer casing of the drum, the condition of the outer turns of the cable is assessed, paying attention to the sheath and protective cover, to smudges of the impregnating composition, to punctures, shells, breaks, displacements and gaps between the turns of the armored tape.

The outer turns of the damaged cable are removed, and its insulation is tested with increased voltage. The paper insulation is checked for the absence of moisture before testing. To do this, paper tapes adjacent to the sheath and cores are immersed in paraffin heated to 150 ° C. Light crackling and foaming indicates wetting of the cable insulation. In this case, a section of 250 - 300 mm is cut off from the end of the cable and a second check is carried out. To avoid errors when testing for cable moisture, the tapes must not be touched by hand. After testing the cable with increased voltage, the sealing caps at the ends of the cable are restored.

The cable laying process consists of the following operations:

1. Installing the cable drum.

2. Lifting the drum with jacks.

3. Removing the casing from the drum.

4. Rolling out the cable by uniform rotation of the drum and pulling the cable along the route to the design position.

When manually rolling out the cable, the cable is pulled by electricians. It is necessary to arrange people in such a way that each of them has a load of no more than 35 kg.

Cables in the cold season are laid without preheating, if the air temperature within 24 hours before the start of work was not lower:

0 gr C - for power armored and unarmoured cables with paper insulation in a lead or aluminum sheath;

7 gr C - for control and power cables with voltage up to 35 kV with plastic or rubber insulation and sheath with fibrous materials in a protective cover;

15 gr C - for control and power cables with voltage up to 10 kV with polyvinyl chloride insulation and a sheath without fibrous materials in a protective cover;

20 gr C - for unarmored control and power cables with polyethylene insulation and sheaths without fibrous materials protective cover.

Heating of cables before laying is carried out indoors. Cable laying is carried out for no more than an hour if the ambient temperature is from 0 to -10 degrees C, no more than 40 minutes at temperatures from -10 to -20 degrees C, and no more than 30 minutes at temperatures below -20 degrees C. At ambient temperature below -40 gr C laying cables of all brands is not allowed.

At a laying temperature below -20 ° C, the cable is heated with electric current throughout the entire rolling period.

Conductive conductors of the inner end of the cable; 2 - heated cable; 3 - conductive cores of the outer end of the cable; 4 - current transformer; 5 - transformer; adjustable transformer.

Power cable termination technology

The cutting of the cable ends is carried out before the installation of couplings and terminations. It consists in the successive stepwise removal of protective covers, armor, shell, screen and insulation over a certain length. The dimensions of the cuts are determined according to the technical documentation.

Coming to the cutting of the cable, they check the absence of moisture in the paper insulation and cores. If necessary, remove wet insulation, excess length of cable ends, other defective places, cutting with sector scissors.

Cutting the cable begins with determining the installation sites of bandages, which are calculated according to the formula: A \u003d B + O + P + I + D.

1 - outer cover; 2 - armor; 3 - shell; 4 - belt insulation; 5 - core insulation; 6 - cable core; 7 - bandage; A, B, I, O, P, G - dimensions of cutting.

At the end of the cable, measure distance A and straighten this section. Next, a resin tape is wound up and a bandage is applied. Available in galvanized steel wire. The ends of the wire are grasped with pliers, twisted and bent along the cable.

The outer cable cover is unwound to the installed bandage, but not cut off, but left to protect the armor from corrosion after mounting the coupling. A second bandage is applied to the cable armor (B) at a distance B (50 - 70 mm) from the first wire bandage. Armor tapes are cut along the outer edge of the bandage with a hacksaw, then this armor is unwound, broken off and removed.

To remove the shell (O) at a distance (50 - 70 mm) from the cut of the armor, ring cuts are made not half the depth. The incision is made with a special knife with a cutting depth limiter and the shell is removed. Next, the cable cores are released from the belt insulation and bent according to the pattern. Then prepare a place for connecting the ground.

To connect the cable cores to the contact terminals of electrical devices, they are terminated with lugs fixed on the cores by crimping, welding or soldering. Termination of single-wire conductors can be performed by forming a ferrule from the end of the conductor.

Laying cables in trenches

The scope of work for laying cables in trenches includes preparatory work, trenching, delivery of drums with cable to the place of work, rolling out the cable and laying it in, protecting the cable from mechanical damage and backfilling the trenches. During the preparatory work, the required amount of brick, sand or sifted earth is delivered to the track, as well as steel or asbestos-cement pipes with an inner diameter of at least 100 mm for the installation of cable line crossings under railways, carriageways and various obstacles located on the cable line route.

When the cable route crosses the pedestrian paths, in appropriate places, transitional bridges with barriers must be installed, delivered to the route in advance. You can start digging trenches after it has been checked according to the plan or with the help of punch holes that there are no underground structures, pipe communications or other cables on the route or dangerously close to it. To do this, the location of underground structures is checked according to the plan, and in the absence of a plan, test pits are made 350 mm wide across the intended route; pits must be dug with great care so as not to damage cables, pipes or other structures that may be in the ground. Long trenches are arranged with special rotary digging trenches, and more often with ordinary earth-moving machines or excavators.

Trenches of short length and passing under asphalt pavements, as well as trenches laid on wall sections where it is impossible to use mechanisms, are dug manually, using a crowbar and a shovel.

The depth of the trench should be at least 700 mm, and the width should be such that the distance between several parallel cables laid in it with a voltage of up to 10 kV is at least 100 mm, and from the trench wall to the nearest outer cable at least 50 mm. The cable laying depth can be reduced to 0.5 m in sections up to 5 m long when the cable is entered into the building, as well as at the points of their intersection with underground structures, provided that the cable is protected from mechanical damage by laying it in asbestos-cement pipes.

In places where the direction of the route changes direction, a trench is dug so that the cable can be laid in it with the required bending angle.

In the places of the future location of cable distribution boxes, the trenches are expanded, forming pits. The pits for one cable sleeve of a cable with voltage up to 10 kV should be 1.5 m deep and 2.5 m long. For each next laid sleeve, the width of the pit should increase by 350 mm.

Dug cobblestones, pieces of asphalt and concrete are laid on one side of the trench or pit at a distance of at least 1 m from their edge to ensure free movement of workers along the route.

Cables are delivered to the place of laying in drums on special cable conveyors or on vehicles equipped with a device for loading, transporting and unloading a cable drum. Unload the drums with the cable carefully so as not to damage it and not injure the workers.

It is strictly forbidden to drop cable drums from motor vehicles or cable conveyors. The cable should be unloaded as close as possible to the place of rolling, but so that it does not interfere with the movement of workers, does not create a threat of falling into the trench and is conveniently located for rolling out.

The cable delivered to the installation site is rolled out from drums using a moving vehicle, a winch on rollers, manually on rollers or without rollers. When rolling out a cable from a moving vehicle from a car or a cable conveyor, two workers manually rotate the drum, winding the cable from it, and two other workers receive and lay the cable in the trench. The cable is wound from the drum from above, not from below. Rolling out is carried out at a speed of a car or a towed conveyor not exceeding 2.5 km/h. When rolling from a drum located on the ground, the latter must be raised above the ground by 200-250 mm using a steel shaft and two cable jacks. Wooden boards with a thickness of at least 50 mm, bricks or reinforced concrete slabs are placed under the jacks.

Before the cable is rolled out, linear and angular rolling rollers are installed in the trench: linear rollers are installed on straight sections of the trench every 2 m, and angular ones - in places of bends and turns of the trench.

Immediately before rolling, remove the sheathing from the cable drum and inspect the upper turns of the cable to make sure that there are no dents, damage to the cable armor or other defects. Then a steel cable is unwound from the drum with a winch and the end of the cable is attached to it. The cable to be rolled is attached to the winch cable using a wire stocking, lopus or lever clamp. A wire stocking is put on the end of the cable and, for a length of at least 500 mm, is firmly fixed on its sheath using three soft wire bandages with a diameter of 0.5 mm, applied over the winding of steel tape. Fastening the cable by means of a stocking has a number of disadvantages, the main of which is the need for a long time to fix the stocking on the cable, the possibility of the stocking slipping off the sheath, and finally, the risk of rupture of the cable sheath near the place where the stocking is applied. When rolling out the cable manually, workers put it on their shoulders and slowly move along the trench or along its bottom. The cable on the shoulders of the workers should not have large bends. The load on each worker participating in the manual rolling of the cable should not exceed 35 kg. The cable must be on the same shoulder for each worker carrying the cable. It is necessary to lower the cable from the shoulders simultaneously and in two stages: first to the level of the lowered arm, and then to the ground. It is strictly forbidden to drop the cable to the ground, in order to avoid accidents or damage to the cable. With an insufficient number of workers necessary for the normal rolling of a cable rated for voltage up to 1 kV at an ambient temperature above 0º C, loop rolling is used. To do this, the cable drum is installed not at the beginning of the trench, but in the middle of its length: half of the cable from the drum is wound from above in one direction, and the remaining half is wound from the bottom of the drum to the other side with a loop brought through the drum.

With the loop method of rolling, it is necessary to observe the permissible bending radii of the cable, and also to exclude its twisting. The cable is laid in a trench in a wave-like manner, with a snake "", in order to create a certain margin of the cable along the length necessary to compensate for the longitudinal stresses that may arise due to subsidence of the soil or temperature changes, the reserve of the cable is also necessary in case of its breakdown. Then the damaged area is removed and the coupling is installed, for which the required amount of cable is used at the expense of the reserve. It is forbidden to create a stock of annular stacked turns, since they will overheat during operation and the cable may fail after a short operation. The cable reserve can be created in the form of an incomplete loop, laid at the end of the line, at vertical risers, at the transition to an underwater route, etc.

Damage and repair of cable lines

Damage to the cable can be caused during operation, which include: drainage of insulation due to movement or runoff of the supply composition; drying of the insulation of cables operating in heavy duty conditions is partly due to the decomposition of the impregnating composition.
The failure of cable lines also occurs due to mechanical damage to cables during laying and re-laying them during operation, corrosion of the metal sheath, which occurs mainly on old cables. During operation, damage to the aluminum sheath of the cable is possible due to a rupture of the hose during installation. Damage to the end and couplings occurs mainly due to non-compliance with the technology of their installation, the use of non-conforming components and materials with an expired date
suitability, as well as couplings that do not correspond to the cross section and U of the cable. Lead couplings are damaged due to poor soldering of the lead body to the cable sheath, the formation of voids during the restoration of insulation with rollers and rolls, not topping up the cable composition, the lack of control over the temperature of the casting and steaming compositions, and the crystallization of the impregnating composition during operation.
Damage to epoxy couplings is associated with the presence of pores and fistulas, lack of sealing. Damage to epoxy terminations occurs due to poor degreasing, processing of the ends of nayrite tubes, sealing of the cores, bending of the cores with an unacceptable bend radius. The main causes of cable (core) breakdowns are as follows: previous damage, direct mechanical damage, corrosion of the metal sheath, soil settlement, laying defects, insulation structure.
Mechanical damages are divided into direct ones, which lead to a simultaneous failure of the cable line, and previous ones, in which the development of a cable defect before breakdown occurs over time and which are detected during testing, and can also cause line failures in operating mode.
Repair work on cable lines is carried out according to a plan developed on the basis of inspection and testing data, as well as an analysis of the general condition of the line. Malfunctions of cable lines or their routes, which pose a threat to trouble-free operation, are eliminated immediately, and malfunctions that do not cause a direct threat to the reliability of the line, - in a smooth manner.
Excavation of cable routes is carried out only with the permission of the operating organization. At the same time, they provide supervision over the safety of cables for the entire period of work, and the opened cables are strengthened to prevent sagging and protect against mechanical damage. Signal lights and warning posters are installed at the work site. The cable line to be repaired is disconnected and grounded. A universal way to repair a cable line is to replace the cable on a section of the route with its tearing, laying a cable insert and preparing couplings. The ends of the open line are closed with a cable insert at the point of damage in such a way that the correct connection of the buses of the same name to each other is ensured. At the repair site, they first check and set the name of the phases, followed by the preparation of the cores.
The repair of the destroyed armor cover is carried out in the following sequence: the damaged part is removed, after which the edge of the armor is soldered to the metal sheath of the cable. The metal shell, unprotected by armor, is coated with an anti-corrosion compound or reeled with plastic tapes.
The nature of the repair of the metal sheath of the cable depends on whether moisture has penetrated into it or not. To do this, remove part of the shell on both sides from the place of its damage and check the top layer of the belt insulation for moisture. If there is no moisture inside the cable, a lead pipe of the appropriate size with two filling holes is placed on the damaged part of the sheath.

The sleeve is filled with cable compound. If there is moisture inside the cable, the damaged area

they cut out and instead insert a piece of cable corresponding to the brand, cross section and length of the one being repaired. A coupling is mounted on both sides of the cable insert.
As a rule, failed terminations are cut out and new ones are mounted. If the cable length is sufficient, the repair is limited to the installation of the termination only. Otherwise, the cable is extended and the coupling is additionally mounted. Leakage of the impregnating composition from the epoxy end seal is possible at the end of the housing, as well as at the exit point of the cores from the termination body. Defects associated with a violation of the tightness of the seal may occur due to poor surface treatment of the nayrite tubes, non-compliance with dimensions, degreasing instructions. Leakage of the impregnating composition at the end of the body of the seal and the exit of the cores from the body is eliminated by installing a repair mold and pouring it with an epoxy compound (rice);

Connection and testing of power cable lines and power cable

The key to high-quality and safe power supply of the facility is reliable power cables. For a successful test of a power cable, it is necessary to give preference to high-quality certified products and you should not save money here, otherwise the life and health of people working or living at the facility may be at risk. These can be wires of our own or domestic production, but the certificates must necessarily indicate compliance with the necessary technical requirements and international standards. Cables can be aluminum or copper. Aluminum ones are a little cheaper, but they also have less electrical conductivity, they quickly oxidize in air, and quickly crumble in places of kinks. Specialists and professionals usually recommend choosing copper, as they have excellent electrical conductivity, are durable and less prone to corrosion. After the completion of all electrical work, the cable is connected.

At the end of the connection and commissioning work, work to check the performance is no less important. They make it possible to determine the insulation resistance between the conductors, as well as the resistance between each of them and the resistance of the conductors to earth. Testing power cables allows you to calculate where a break has occurred in the cable cores or the presence of asymmetry in the insulation. Tests are carried out in strict accordance with GOST, and for each of them there is a diagnostic method that is chosen by a professional specialist, and his choice directly depends on the situation. Power cable - a universal cable designed for continuous uninterrupted supply of electricity from transformers to various objects - utility complexes and enterprises. There are situations when the cable changes its parameters due to temperature effects or other factors, so professional diagnostics are needed here. Connecting the cable is a rather responsible job, which requires the involvement of highly qualified specialists who know the various methods of testing them and can accurately diagnose the condition. This is important not only for security, but also to ensure their functionality and the smooth operation of the facility.

Power cable repair and cable termination installation

Mounting the cable gland

During the service life of cable lines, various damages may occur to eliminate which require cable repair. If current repairs of cable lines are carried out, then they mainly carry out the following work: they inspect cable channels, clean the routes of couplings, cables laid in an open way, check cable end couplings, straighten the cable, restore the marking, determine the heating temperature of the cable, its degree of corrosion shells. The grounding is also checked, the identified defects are eliminated, the condition of the cable wells is monitored, access to them is monitored, if necessary, some sections of the cable line are re-layed, couplings are installed, and they are topped up with mastic.

Installing the cable gland

In cases where the cable insulation is broken, a sleeve must be installed on the cable for repair. The coupling is designed to connect different types of cable. The installation of a connecting sleeve is used when carrying out repair work on damaged cable lines to ensure a reliable and durable connection of different cables, tie-in to the network, transfer of a cable line. Installation of the termination is necessary when connecting the cable line to the electrical network, installation, etc.

Installation of the sleeve on the cable must be carried out carefully, in compliance with the technical requirements. If the coupling is installed unprofessionally, without observing a certain technology, as well as if the cross section is incorrectly selected or if the voltage is not matched, it may be damaged. Regardless of which couplings are used - connecting, transitional or cable end couplings, they must be of high quality.

Cable repair

During the overhaul of cable lines, complete or partial replacement of network sections, installation of cable boxes, painting of structures, replacement of identification marks, installation of additional protection in places of possible damage to the cable are carried out.

Installing the cable gland

If it is necessary to repair the cable that is laid in the trench, then the coating is removed, the trench is excavated. When excavation is carried out, warning signs must be installed next to the trench. When carrying out a complete replacement of a damaged section, repairing 10 kV cable lines, you must comply with the established requirements, take into account the type of soil, the proximity of engineering structures, use only recommended materials that provide reliable cable protection. The permissible tensile forces are also controlled, for this a dynamometer is used.

When repairing cable lines of 0.4 kV or 10 kW, the cable is laid with a certain margin in order to avoid mechanical stress when the soil moves and the temperature changes. If the cables are laid in a trench in parallel, then their ends, where the installation of couplings is supposed to be installed, are located at a distance of at least 2 m from each other. It is also necessary to provide a margin for the behavior of the insulation moisture test, not only for the installation of the coupling, but also for their re-cutting in the event of damage. In limited conditions, the installation of cable glands can be carried out slightly below the level of the main cable installation.

Repair of cable lines of 0.4 kV or others is carried out in accordance with a plan that is developed on the basis of data obtained during inspection and testing. Without fail, all work is coordinated with operating and controlling organizations. There are several technologies with the help of which 10 kV, 0.4 kW cable lines are repaired. A universal option - ripping the route, laying a cable insert, installing cable sleeves. When carrying out repairs, it is imperative to achieve phase connection. Correct installation of the end coupling helps to achieve this.

All repair work (installation of cable glands, replacement of cable sections, etc.) must be carried out by professional specialists with access to such work and proper experience.

Remote cable piercing, cable piercing, remote cable piercing device

Trenchless laying method - cable puncture method

In recent years, the trench method has been used less and less for laying a cable or pipeline. Taking care of the appearance of the city, the authorities forbid spoiling it if, for example, the cable path passes through the road (including the railway), water and other objects. In this case, the cable is laid using the puncture method: the cable, using a specially dug well, is laid horizontally underground without damaging or affecting objects on the surface.

The method of remote cable puncture is used for laying communication cables, electric cables, and the puncture method is also used for laying engineering communications pipes (gas pipeline, water supply, sewerage). About 90% of all work during laying by remote cable puncture is carried out underground. In European countries, the puncture method is used in 95% of cable laying cases, and in Russia it is becoming more common.

Advantages of cable laying using the puncture method:
saving money and time due to fast work without digging trenches,
the ability to pierce a cable up to 150 meters long,
no surface damage
no damage to already existing underground utilities,
the possibility of laying cables at any time of the year,
remote cable puncture does not require the presence of a person at the place of laying underground, and all work is controlled remotely from the surface,
cable puncture is performed in just one shot,
the possibility of not only laying a new cable, but also replacing the old one.

Since the cable puncture is carried out remotely, without the direct presence of an employee at the place of laying underground, special devices are called "remote cable puncture devices" (manual mechanical drive, electric drive or pyrotechnic). The remote cable piercing device allows puncturing in any conditions (trenches, basements, cable ducts, collectors, etc.) with a gap between cables of 30 mm and in any spatial position.

The remote cable piercing device ensures the safety of workers during repair and maintenance work in existing installations, preventing electric shock to workers during cable puncture.

So, if you are faced with the task of laying a cable, do not hesitate to contact our company, which will offer you fast, high-quality work on laying a cable using the puncture method._

• Order products on the site.
• Online store of electrical products.
• LLC "ElTeks" Contacts: +79184692483 +79184822755 [email protected]
• We will represent your interests in the Krasnodar Territory and the Southern Federal District. Deliveries of any electrical products according to your details.
• Everything for electrical and cable work. Everything for electrical installation organizations.
• Supply of electrical products for electrical, construction and trade organizations, etc.
• Heat-shrinkable cable sleeves POLT, POLJ, GUST, GUSJ, SMOE, EPKT, TRAJ and other Raychem systems for any cable. RICS adapters, etc. Cable repair sleeves.
• Heat-shrinkable cable sleeves KVTp KNTp STp for any cable
• Cable glands "Cellpack Electrical Product"
• Cable sleeves, adapters, cable cutting tool EUROMOLD and Nexans Company. Cable accessories, adapters, tools Euromold , GPH , Tyco Electronics Raychem
• Cable couplings of the firm 3M and other factories. Tension couplings. Couplings for submarine cable and self-regulating heating cable.
• Heat-shrinkable cable repair sleeves. Heat-shrinkable cable passage seals UKPT.
• Tool for cable and electrical work incl. removal of insulation from any cable. Knives for cable and electrical work
• Stripping tool for any cable, including XLPE cable
• Sets of tools for cable and electrical work, including the removal of insulation from any cable. Tool kits for electrician, electrician, cableman, cable welder, relayer, welder, battery man, etc.
• Tool for electrical installation organizations.
• Everything for rewinding, unwinding, winding, pulling a cable, wire, cable, rope. Equipment, machine tools, racks, racks, rollers, swivels, jacks, rollers, etc. Cable length meters.
• Cable rewinding and pulling equipment. Cable jacks.
• Lubricants (UVS) Superkont, Primakont and Extracont for protection of electrical contact connections from overheating and oxidation.
• Machines for rewinding, unwinding, winding cable. Cable layers. Hydraulic tensioners. Cable pushers.
• Electrical assembly gunpowder tool.Devices for remote and mechanical cable puncture.Powder press.
• cable rollers. Cable jacks. Cable stockings. UZK 11/150. UZK 11/200. Mini ultrasound.
• Cable adapters KPRKO-20, 90-120 sq. mm and KPRKO-20, 240 sq. mm
• Cable straight and angled rollers, cable stockings for cable pulling and SIP.
• Cable stockings are standard, through, supporting, mounting for laying cable lines and self-supporting insulated wire.
• Device for harvesting cable channels UZK 11/100, UZK 11/150, UZK 11/200, etc. for cable pulling. Mini UZK.
• Winches manual, electric, with the petrol and diesel drive for cable works. Autonomous capstan traction winches LTA-1, LTA-3, LTA-5, LTA-8.
• Heat-shrinkable tubes, tapes, mouthguards, gloves, cuffs for electrical and cable work
• RAYCHEM Electrical Heat Shrinkable Products
• Lugs and connectors for cable and SIP
• Sector and hydraulic shears for cutting any cable, incl. with armor insulation. Cable sector shears for cutting armored and plain cables NS-14, NS-45, NS-50 Bs, NS-70 BS, NS-75BS, NS-80 BS, NS-90 BS, NS 100 BS, NS 110 BS, NS -130 BS. and etc
• Mechanical and hydraulic presses for crimping tips, sleeves, connectors, any hardware clamps. Hydraulic press PG 70, PG-120, PG-300, PG-400, etc.
• Presses for working with current-carrying tires. Metal perforation. Sheet metal punching tool. Equipment for processing copper and aluminum busbars. Shinogi, shinoreza, shinodyry.
• Measuring machines for rewinding, unwinding wire and cable for stores and warehouses.
• Racks for cable drums. Winding and rewinding machines for cable. Coil winding racks.
• Cable and wire length meters. Length meters for rewinding fabric, linoleum, roofing felt, film, rope, ropes, hose, molded products and other materials of flat and round cross-section. Measurement of the length of profiles and pipes of steel, aluminum, plastic strip / tape, furniture edge.
• Dielectric fiberglass ladders, ladders, scaffolds. Ladders transformers. Fiberglass ladders, etc. Dielectric ladders, ladders, scaffolds, stools - SV, SSS, LSP, LSPR, LSPD, LSPR, SSD, SVD, PI, LSPSO, etc. for electrical work.
• Fiberglass dielectric ladders for electrical work.
• Accessories for cable glands
• Means and devices for electrical protection of personnel
• Electrically conductive lubricants EPS 90, EPS 98, EPS 150, EPS 200, EPS 250, EPS 300 for movable, fixed and sliding contacts. Lubricants for cable pulling. Special lubricants.
• Tension and coupling fittings. Insulators for high voltage lines. Traverses, etc.
• Telephone couplings, tools and bales for telecommunications
• Heat-shrinkable telephone sleeves TUM-K, TUM-KS, TUM-KP, TUM-Ku, TUM-Kr, etc.
• Multifunctional ladders, step-ladders, platforms, scaffolds, transitions, etc. for construction work.
• Industrial cable strippers
• Epoxy, lead and control cable glands.
• Cable and conductor products. XLPE cable, etc.
• Fittings and tools for SIP
• Cable ties for bundling wires and cables
• Electric heaters Nobo and Dantex
• Measuring instruments and test equipment for the power industry. Devices for electrolaboratories.

Maintenance and repair. To ensure the uninterrupted operation of cable lines and networks of automation, telemechanics and communications at signaling and communication distances, teams of cablemen and cable workshops are organized. Employees of the cable shop monitor the technical condition of cable lines and networks, repair cables, terminal and intermediate devices, underground wells and cable ducts, prepare the cable industry for work in winter, and also eliminate damage to cables.

Scheduled and control electrical measurements of all types of cable at distances with large cable networks are carried out by employees of the RTU measuring group.

A certain procedure for maintenance and overhaul has been established.

During the current maintenance of cable lines, the condition of the cable route, cable structures, cable accessories (cabinets, boxes, plinths, various couplings, etc.) is checked and the identified defects are eliminated. They make sure that earthworks that have not been agreed upon in advance are not carried out on the cable laying route, eliminate damage, take measures to protect the cable from corrosion, etc. More complex and time-consuming work that cannot be performed by personnel conducting routine maintenance is performed during the overhaul of cable lines.

Major repairs are carried out according to pre-compiled projects and estimates. The estimates include the relocation and replacement of individual sections of cables with reduced core insulation resistance, which cannot be restored. Major repairs are planned in advance and carried out by special teams for labor-intensive work.

At distances with telephone sewerage, during the overhaul, dilapidated cable wells are rebuilt, damaged channels are restored and channels are additionally laid from asbestos-cement pipes.

The overhaul plan provides for the deepening of the cable trench in separate sections, the connection to the air pressure cable. Carry out work to protect against electrical and soil corrosion with the inclusion of drainage, replace measuring posts, repair or replace faulty boxes, replace non-standard hatches with standard ones, take measures to isolate wells from water ingress, etc.

Upon completion of the work, the repaired sections of the cable line are accepted by a special commission.

Rice. 96. Scheme of installation type USKD-1

cables occur due to the penetration of moisture into it in case of violation of the tightness of the sheath due to corrosion, violation of laying rules, poor-quality soldering of cable sleeves and mechanical damage caused by soil displacements or careless earthworks along the cable route. To protect the cable from the penetration of moisture into it if the integrity of the shell is broken, the cable lines are kept under constant overpressure, which makes it possible to control the tightness of the shell and determine the location of its damage. In addition, in case of minor damage to the sheath, the flow of gas escaping at the place of its damage prevents moisture from penetrating inside the cable, which increases the reliability of cable lines.

When the cable is kept under constant overpressure, the cable line is divided into sealed sections, called gas sections. For multi-channel communication cables, the length of the sections, as a rule, is equal to the length of the amplifying section of high-frequency circuits. At the ends of the gas section, as well as on all branches from the main cable, gas-tight couplings are installed. Excessive gas pressure is created inside the gas sections.

There are two systems for containment of pressurized cables: with automatic and periodic filling of cables with gas. On cable lines of multichannel communication of the MPS, the system with automatic filling is most widely used. In this system, at the ends of the gas section, automatic control and drying installations AKOU, and more recently - USKD installations, are placed. Dry air is used as the gas.

Installation type USKD-1 (Fig. 96) provides automatic supply of dry air to the cable, control of gas flow, signaling of a violation of tightness and a decrease in pressure in a gas cylinder. From the high pressure cylinder 1 (10, 15 or 20 MPa) (or from the compressor) through the high pressure drying chamber 2, gas is supplied to the reducer 4 with a check valve (the check valve is necessary to disconnect the cylinder from the installation when the pressure drops to 2 MPa), then into the low pressure reducer 5, at the outlet of which a stable pressure of 50+ 2 kPa is formed, which is automatically maintained at a gas flow rate of not more than 3 m/min. Next, the gas passes through a low-pressure drying chamber 12, a pneumatic signaling device 6 and a block of rotameters 7. In the block of rotameters, after passing through a humidity indicator 10, the gas enters the rotameters 9 to control the gas flow by each cable and through the fitting 8 to the cables. The safety of the installation is ensured by safety valves. The signaling of the cable tightness control is carried out using a pneumatic signaling device 6, and the signaling of a decrease in pressure in the cylinder is carried out by an electrocontact pressure gauge 3. The pressure gauge 11 controls the pressure of the gas supplied to the cable.

The USK.D-1 type equipment provides for the connection of an air control device of the VKP-1 type to determine the area of ​​non-tightness of the cable sheath by gas flow.

The exact location of the shell damage is determined using indicator gases. To do this, a valve is soldered into the coupling closest to the border of the damaged area and the excess pressure is reduced (the valve is opened for 20-30 minutes). Within 5-10 minutes, freon is introduced into the cable at a pressure of 50-60 kPa. To ensure the movement of gas along the cable, dry air is injected at a pressure of 50-60 kPa. 12-15 hours after the introduction of freon, they begin to examine the route, for which, after 1.5-2 m above the cable, pits with a diameter of 2 cm and a depth of 25-30 cm are arranged. Using a leak detector (a device that reacts to the presence of freon), an air sample is taken in the shafts. The maximum gas concentration will be directly above the cable fault.

The most characteristic damage to a cable in operation is a gradual or sharp decrease in the insulation resistance between the cable cores and between the cores and the ground (metal sheath). The cause of these damages is the penetration of moisture into the cable if it is not kept under constant air pressure. Damage is also observed, such as a break in one or more cable cores, a short circuit of a part of the cores between themselves or with a lead sheath.

First you need to accurately determine the location of the damage. If the cable is under excessive air pressure, in a system with automatic gas supply, it is sufficient to know the number of doses of gas supplied to the cable when its sheath is damaged. This is determined using automatic dispensers of AKOU or USKD installations located at stations that limit the damaged section of the cable. If the cable is not held under positive gas pressure, then the location of the cable damage is determined by electrical measurements or by means of tracer gas. A more advanced method is to detect the damage site using freon, when the cable route is accurately marked in the area of ​​​​its damage.

To find the cable route, it is most convenient to use a cable finder, which consists of a tone frequency generator that can operate in a pulsed mode and in a continuous oscillation mode. One output of the generator is connected to the cable cores, which are grounded at the opposite end, and the other output is connected to ground. From the generator, alternating current passes through the cores of the cable, the route of which is being searched, and returns along the ground to the generator. At the same time, the current around the wires creates an alternating magnetic field that changes with a frequency of about 1000 Hz.

The indicator of the cable route is a finder coil (ferrite antenna) connected to the input of a transistor tone frequency amplifier, at the output of which a headphone is connected. The ferrite antenna is fixed on the sector, which, in turn, is pivotally mounted on the finder's handle (rod). By rotating the sector, the ferrite antenna can be rotated to a vertical and horizontal position, as well as fixed at angles of 30, 45 and 60°.

The cable route is preliminarily found by the maximum signal volume in the telephone, when the antenna axis is perpendicular to the cable axis, and it is refined by the minimum signal volume, when the antenna axis is parallel to the cable axis.

After determining the cable route in straight sections, it is marked with stakes installed every 5-10 m, in curved sections - at shorter intervals. Then, on the route, every 1.5-2 m, pits are made in the ground - holes with a diameter of 1.5-2 cm and a depth of 30 cm and determine the place of leakage of the cable sheath using freon. To do this, a connecting cast-iron sleeve is opened near the supposed site of damage to the shell, and a valve is soldered into the lead sleeve, through which from 400 to 800 g of freon is introduced under a pressure of about 60 10 3 Pa. Freon is injected using a field installation for the introduction of indicator gas (PUVIG), consisting of a cylinder with freon, a drying chamber with a humidity indicator and two pressure gauges. Air is pumped from the ends of the cable, which accelerates the spread of freon. Freon spreads through the cable and through the place of damage to the shell to the surface of the earth from 12-15 hours to one day, depending on the density of the soil.

After this time, the location of the shell damage is determined. For this, a battery halide leak detector is used, consisting of a measuring unit, a power supply unit and an external probe. Moving along the cable route, one by one insert the probe of the device into the previously prepared pits. At the point of damage to the cable sheath, freon will accumulate in the pit and a halide leak detector will signal this. Having found the place of damage to the cable sheath, proceed to its repair.

If other damage occurs in the cable (breakage of the cores or shorting of the cores to each other), the location of the cable damage is determined using electrical measurements.

Operation of cable lines and networks in winter conditions. For trouble-free operation of cable lines and networks in winter conditions, even before the onset of cold weather, a number of preventive measures and preparatory work are carried out. First of all, they inspect cable lines, networks and cable inserts, identify the weakest points and eliminate the detected defects. To check the condition of the existing cable, electrical measurements of cable circuits are carried out. Carefully inspect the terminal cable devices (terminals, boxes, cable boxes, etc.). Check whether the doors and covers in the cable boxes are tightly fitted, since if there are gaps in winter, snow can penetrate there; inspect cable supports, supports and guy wires.

Before the onset of cold weather, the cable ducts are carefully checked. Particular attention is paid to the fact that there is no water in the sewer channels and wells, which, when frozen in winter, can strongly squeeze the cable laid in the channels and damage it. After inspecting the wells, the top covers of the manholes are coated to prevent water and dirt from entering the well during the autumn rains.

Additional work on the current maintenance of cable lines and networks in winter includes: clearing the hatches of cable wells, distribution cabinets and other cable fittings installed in the open air from snow; more careful monitoring to ensure that no cracks appear in the cable mass with which the terminations are protected due to strong fluctuations in the ambient air temperature; ice chips on submarine cables, if, due to a significant drop in the water level, the cable is frozen into ice off the coast.

On cable and overhead lines with submarine cable inserts, inspect the condition of these inserts and find out if there is a danger of damage to the submarine cable by ice drift. At local hydrometeorological stations, they find out the time of the expected ice drift and the magnitude of the expected flood. Reinforce cable supports that may be in the spill area. Before the onset of ice drift, in places where an underwater cable is laid and there is a risk of damage, they arrange constant duty of workers and special teams provided with an emergency supply of materials, boats, etc. On sections of the route where landslides and erosion of the soil can occur, they also take measures to prevent damage - arrange drainage, etc.