Planned, emergency and urgent cable repair. "Operation of power supply systems

cable network damage repair

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 needed 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 of 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.

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 indefinitely. 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.

Couplings for 20 and 35 kV cables 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 coupling 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, which manifests itself in the form of 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 earth's surface 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 entering the input of 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 backup line is heavily overloaded and consumer limitation 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 a voltage of up to 10 kV should be 1.5 m deep and 2.5 m long. For each next laid sleeve, the pit width 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 composition. 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._

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Repair of cable lines is carried out on the basis of data obtained during inspections and testing of cables. A feature of cable repair is that the repaired cables, as being in operation, can remain energized or have a residual charge. In addition, they may be located near live cables that are energized. All this requires maintenance personnel to pay special attention not only to personal safety, but also to avoid damaging nearby cables, and therefore it is important to carry out repairs in the shortest possible time, since during repairs it is necessary to switch to less reliable temporary power supply schemes.

Repair work on cables is often associated with excavation of cable trenches. more than 80% of cable failures and 90% of coupling failures occur when laying cable lines in trenches. To avoid damage to nearby serviceable cables and other utilities, it is necessary to have accurate information about the location of underground utilities. After reaching a depth of 0.4 m, excavation is allowed to continue only with shovels. The use of jackhammers, crowbars and other tools for loosening the soil is strictly prohibited. If cables or any other underground communications are found during earthworks, the work is stopped and the person responsible for the work is notified about this. After opening, open cables and couplings are strengthened on a board, which is suspended from the bars thrown over the trench.

The main work on the repair of cable lines can be reduced to three types: repair of the armor cover of cables, repair of the lead sheath of cables, repair of couplings and terminations.

In case of local destruction of the cable armor, the defect is eliminated as follows. In the place of destruction, the rest of the armor is removed, the edge of the armor is soldered to the lead sheath of the cable, which is coated with bitumen-based anti-corrosion varnish. For cable lines laid in the ground, the armor cover is not repaired during operation. If it becomes necessary to repair the lead sheath of the cable, then pay attention to the nature of the damage. If damage to the cable insulation and the penetration of moisture into the inside of the cable is excluded, the repair is reduced to the restoration of the lead sheath. To do this, a lead pipe is made 70-80 mm larger than the bare part of the cable. The bare section of the cable is placed in a prepared lead pipe, the seam of which is sealed. In the same case, when the penetration of moisture into the cable is not excluded, it is necessary to check the paper insulation of the cable in the defective place for the absence of moisture. Paper insulation tapes removed from the cable at the point of damage are immersed in paraffin heated to 150 ° C. If there is moisture in the insulation, immersion of the insulation in paraffin will be accompanied by crackling and foaming from it. When establishing the fact of moisture penetration under the lead sheath of the cable, the damaged section of the cable is cut out, a segment is inserted instead and two couplings are mounted at both ends.

When repairing couplings, it is sometimes possible to avoid the use of cable inserts: using new couplings of greater length (elongated), which make it possible to increase the length of the cable cut. In case of failure, the termination is cut out or dismantled, then the cable insulation is checked for moisture content. If moisture has not penetrated into the cable, they are limited to installing a new or repairing a damaged coupling. When moisture penetrates into the cable, the defective section is cut out and a new termination is mounted.

Safety engineering. An important condition for ensuring the safety of personnel during the repair of cable lines is the performance of work on orders and by at least two persons. Repair work is allowed to be carried out only after a comprehensive disconnection of the repaired cable. Checks at its ends for the absence of voltage and hanging in places where voltage can be applied to the repaired cable, posters “Do not turn on - people are working”:

When repairing cable lines, it is sometimes necessary to cut the cable or open the sleeve. Such work can be carried out after making sure that the cable is not energized. The check is carried out with a special piercer equipped with an insulating rod.

During repair work in cable structures (tunnels, collectors, channels, etc.), as well as during excavation of cable routes, before starting work, using a special device, it is established that there are no gases harmful to breathing. If they are detected, workers are not allowed to work until the gas is removed.

In order to avoid fires during the repair of cables, it is allowed to heat the cable and fill the blowtorch with gasoline outside the cable structures.

When testing power cables with high voltage direct current from a kenotron installation, it must be protected and removed from the place of work before testing. The test set must be grounded before testing. Cables should be connected and tested with dielectric gloves, standing on an insulating base. At the end of the cable test with direct current, all cable cores are discharged from the accumulated electric charge through the limiting resistance provided for this purpose in kenotron installations.

Control questions

1. How is the acceptance of cable lines hidden laid cables?

2. What is the frequency of maintenance of cable lines up to 35 kV?

3. What are the terms of CL inspection?

4. What types of inspections are there?

5. What is the purpose of preventive testing?

6. Who sets the frequency of preventive tests and what is its frequency?

7. When is cable termination inspected?

8. What is controlled when inspecting openly laid cables in cable structures?

10. What type of CL laying accounts for the most failures?

11. How are couplings repaired?

12. What are the main conditions for ensuring safety during the repair of cable lines?

During the service life on cable lines, various damages may occur to eliminate which is required. cable repair.

In accordance with the requirements of the “Instructions for the operation of power cable lines. P 1. Cable lines with voltage up to 35 kV "each cable line must be subject to current or major repairs.

Maintenance can be emergency, urgent and planned.

emergency a repair is such a repair when, after disconnecting the cable line, consumers of all categories were 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 there is no possibility of further unloading or restriction of consumers is required.

Urgent a repair is such a repair when receivers of the first or especially important second category are deprived of automatic backup power, and for receivers of all categories, the load on the remaining cable lines causes their overload or limitation of consumers. Repair crews begin urgent repairs of cable lines at the direction of the energy service management during the work shift.

Planned repair is the repair of all cable lines not listed above, which is 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 cable lines is produced according to the annual plan, developed annually in the summer for the next year on the basis of operating data. During the overhaul of the cable line, perform partial or complete replacement of sections of the cable network, painting 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.

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 all work related to the serviceability of lighting, ventilation, water pumping devices, fire fighting equipment. 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, preparatory work, preparation of the workplace, preparation for installation are carried out.

Repairs of cable lines are simple that do not require a lot of labor and time, and complex when the repair lasts several days

Complicated repairs are carried out by one or more teams, and if necessary around the clock, using 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

Installation cable box performed if the cable insulation is broken. 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 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.

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

Proper organization of maintenance work, professional repair of the power cable, competent installation of the coupling, timely detection of problem areas and defects ensure long-term operation of cable lines and their reliable uninterrupted power supply.

Various reasons can lead to the failure of cable lines, from natural wear of insulation and mechanical damage to the cable to errors in calculations and incorrect actions of maintenance personnel. In turn, damage to cable lines often leads to emergencies, fires, fires and electric shocks. To prevent such consequences, it is necessary to regularly measure the insulation resistance of cables. You can solve this problem in two ways:

1. Provide staffing for specially trained people with a clearance group necessary for the implementation maintenance and repair of cable communication lines and power cables.
2. Entrust such work to professionals by concluding a contract for the maintenance of cable lines.

Repair of power cable lines

If the power cable is damaged, the power supply through it stops. In this case, you need:

• Determine and eliminate the cause of cable damage so that when power is applied after repair work, the already repaired section does not fail.
• Using special tools, find the location of the cable damage.
• Repair the cable line. Depending on the scale of the damage, it may be local or require replacement of the entire section of the cable line. Cable workers perform the necessary mechanical work with the cable route (open / close the trench, install couplings, cut / strip the cable, etc.). At the same time, they actively interact with the workers of the electrical laboratory, who indicate the problem area, perform current control and final check before applying voltage.

Installation and repair of power cable lines 10/ 6/ 0.4 kV must be carried out by trained and licensed personnel. To eliminate the damage, it is necessary to cut the cable in the area of ​​damage and install a cable coupling. It is used for reliable connection, termination or branching of power cables, as well as for their connection to overhead power lines and electrical devices.

In the process of cutting the cable, all its layers from the outer sheath to the phase insulation of the current-carrying core are sequentially removed with some shift. This is done to further strengthen or repair the insulation, or to replace the damaged area with an insert. Installation of the coupling is a complex and responsible work that allows you to restore the properties of the cable line, lost due to damage. Such operations are carried out by electrical couplers who have undergone special training and have received permits for such work.

Repair of communication cables

First of all, broken connections are switched to working pairs, and electrical measurements and a thorough inspection are carried out to determine the area of ​​damage. The cable route is viewed, viewing devices are opened, rupture zones are checked, and air pressure is determined. If the problem area is located within the viewing device, after removing the coupling, this gap is dried.

If individual pairs of cores are damaged, the plinth opens and is viewed from the inside. The cores are soldered, burrs and solder runs are smoothed out, the core or pin is insulated, the pin is adjusted and other repair operations are performed. The plinth can be dried with hot air or washed with cable mass. Broken terminals need to be replaced. Upon completion of the repair, the operation of the connections is checked.

Repair of a fiber-optic communication line (FOCL)