Characteristics of human lesions electric shock. Electrical resistance of the human body. 2

The main causes of electric shock. 3

Methods and means used. 4

for protection against electric shock. 4

when touching metal non-current-carrying parts, 4

under tension. 4

Organizational measures to ensure the safety of work in electrical installations. 4

Technical measures to ensure the safe performance of work in operating electrical installations. 4

Characteristics of electric shock to a person. Electrical resistance of the human body

Electric current, passing through the human body, has a biological, electrochemical, thermal and mechanical effect.

The biological effect of the current is manifested in irritation and excitation of tissues and organs. As a result, skeletal muscle spasms are observed, which can lead to respiratory arrest, avulsion fractures and dislocations of the limbs, and spasm of the vocal cords.

The electrolytic effect of the current is manifested in the electrolysis (decomposition) of liquids, including blood, and also significantly changes the functional state of cells.

The thermal effect of electric current leads to burns of the skin, as well as the death of underlying tissues, up to charring.

The mechanical effect of the current is manifested in the stratification of tissues and even the separation of body parts.

Electrical injuries can be conditionally divided into local, general (electric shocks) and mixed (local electrical injuries and electrical shocks at the same time). Local electric shocks make up 20% of the considered electric injuries, electric shocks - 25% and mixed - 55%.

Local electrical injuries- clearly expressed local disorders of body tissues, most often these are superficial injuries, i.e. damage to the skin, sometimes soft tissues, as well as articular bags and bones. Local electrical injuries are cured, and a person's working capacity is restored completely or partially.

Typical types of local electrical injuries- electrical burns, electrical signs, skin plating, electrophthalmia and mechanical damage.

The most common electrical injury is electrical burns. They make up 60 - 65%, and about 1/3 of them are accompanied by other electrical injuries.

There are burns: current (contact) and arc.

Contact electrical burns, i.e., tissue damage at the points of entry, exit and on the path of electric current flow occurs as a result of human contact with the current-carrying part. These burns occur during the operation of electrical installations of relatively low voltage (not higher than 1-2 kV), they are relatively light.

arc burn due to the influence of an electric arc that creates high temperature Arc burn occurs when working in electrical installations of various voltages, often the result of accidental short circuits in installations above 1000 V and up to 10 kV or erroneous operations of personnel. The defeat occurs from the flame of an electric arc or clothing caught fire from it.

There may also be combined lesions (contact electric burn and thermal burn from the flame of an electric arc or ignited clothing, electric burn in combination with various mechanical damage, electric burn simultaneously with thermal burn and mechanical injury).

According to the depth of the lesion, all burns are divided into four degrees: the first - redness and swelling of the skin; the second - water bubbles; the third is the necrosis of the superficial and deep layers of the skin; the fourth - charring of the skin, damage to muscles, tendons and bones.

electrical signs are clearly defined spots of gray or pale yellow color on the surface of the skin of a person who has been exposed to current. Signs are round or oval with a depression in the center. They come in the form of scratches, small wounds or bruises, warts, skin hemorrhages, and calluses. Sometimes their shape corresponds to the shape of the current-carrying part that the victim touched, and also resembles the shape of lightning. In most cases, electrical signs are painless and their treatment ends well. Signs occur in about 20% of those affected by the current.

Skin metallization- penetration into its upper layers of particles of metal melted under the action of an electric arc. This is possible in case of short circuits, trips of disconnectors and knife switches under load, etc.

The affected area of ​​the skin has a rough surface, color
which is determined by the color of the metal compounds on the skin:
green - in contact with copper, gray - with aluminum, blue -

green - with brass, yellow-gray - with lead.

Metallization of the skin is observed in approximately 10% of the victims.

Etectroophthalmia- inflammation of the outer membranes of the eyes as a result of exposure to a powerful stream of ultraviolet rays. Such exposure is possible in the presence of an electric arc (for example, during a short circuit), which is a source of intense radiation not only of visible light, but also of ultraviolet and infrared rays. Electrophthalmia occurs relatively rarely (in 1-2% of victims), most often during electric welding.

Mechanical damage occurs as a result of sharp, involuntary, convulsive muscle contractions under the influence of current passing through the human body. In this case, ruptures of the skin, blood vessels and nervous tissue are possible, as well as dislocations of the joints and bone fractures. Mechanical damage - serious injuries; their treatment is long. They occur relatively rarely.

electric shock- this is the excitation of body tissues by an electric current passing through it, accompanied by muscle contraction.

Distinguish four degrees of electric shock:

I - convulsive muscle contraction without loss of consciousness;

II - convulsive muscle contraction with loss of consciousness, but with preserved breathing and heart function;

III - loss of consciousness and impaired cardiac activity or breathing
niya (or both together)

IV - clinical death, i.e. lack of breathing and blood circulation,
The danger of exposure to electric current on a person depends on

the resistance of the human body and the voltage applied to it, the strength of the current, the duration of its impact, the path of passage, the type and frequency of the current, the individual properties of the victim and other factors.

The electrical conductivity of various tissues of the body is not the same. Cerebrospinal fluid, blood serum and lymph have the highest electrical conductivity, followed by whole blood and muscle tissue. The internal organs, which have a dense protein base, brain substance and adipose tissue, conduct electrical current poorly. The skin and, mainly, its upper layer (epidermis) has the greatest resistance.

The electrical resistance of the human body with dry, clean and intact skin at a voltage of 15 - 20 V is in the range from 3000 to 100,000 ohms, and sometimes more. When the top layer of the skin is removed, the resistance decreases to 500 - 700 ohms. With complete removal of the skin, the resistance of the internal tissues of the body is only 300 - 500 ohms. When calculating, the resistance of the human body is taken equal to 1000 ohms.

The resistance of the human body depends on the sex and age of people: in women, this resistance is less than in men, in children it is less than in adults, in young people it is less, NR IN THE ELDERLY: THIS is due to the thickness and degree of coarsening of the upper layer of the skin.

The electrical resistance is also affected by the type of current and its frequency. At frequencies of 10 - 20 kHz, the upper layer of the skin practically loses resistance to electric current.

The main causes of electric shock

1. Accidental contact with live parts under voltage as a result of: erroneous actions during work;

malfunctions protective equipment with which the victim touched current-carrying parts, etc.

2. The appearance of stress on metal structural parts
electrical equipment as a result of:

damage to the insulation of current-carrying parts; network phase closure to ground;

falling wire under voltage on the structural parts of electrical equipment, etc.

3. The appearance of voltage on disconnected current-carrying parts in re
Result:

erroneous inclusion of a disabled installation;

short circuits between disconnected and energized live parts;

lightning discharge into an electrical installation, etc.

4. Emergence step voltage on the land where
person as a result:

phase-to-earth short circuit;

removal of the potential by an extended conductive object (pipeline, railway rails);

malfunctions in the protective earthing device, etc.

Step Voltage - the voltage between two points in a current circuit that are one step apart from one another and where a person is standing at the same time.

The highest step voltage is near the fault, and the lowest is at a distance of more than 20 m.

At a distance of 1 m from the ground electrode, the step voltage drop is 68% of the total voltage, at a distance of 10 m - 92%, at a distance of 20 m - almost equal to zero.

The danger of step voltage increases if the person who has been exposed to it falls: the step voltage increases, since the current no longer passes through the legs, but through the entire body of a person.

Methods and means used

for protection against electric shock

when touching metal non-current-carrying parts,

under tension

To protect against electric shock when touching metal non-current-carrying parts that are energized, the following methods and means are used:

protective grounding, grounding, potential equalization, system of protective conductors, protective shutdown, insulation of non-current-carrying parts, electrical separation of the network, low voltage, insulation control, compensation of earth fault currents, personal protective equipment.

Technical methods and means are used separately or in combination so as to provide optimal protection.

Organizational measures to ensure the safety of work in electrical installations

Organizational measures that ensure the safety of work in electrical installations are:

registration of work with a work permit, order or list of works performed in the order of current operation;

work permit;

supervision during work;

registration of a break in work, transfers to another workplace, termination of work.

Technical measures to ensure the safe performance of work in existing electrical installations

In accordance with the requirements of the Safety Rules for the operation of consumer electrical installations, to prepare the workplace during work with stress relief, the following technical measures must be performed in the specified order;

the necessary shutdowns have been made and measures have been taken to prevent the supply of voltage to the place of work due to erroneous or spontaneous switching on of the switching equipment;

prohibitory posters are posted on the manual drives and on the remote control keys of the switching equipment;

the absence of voltage on current-carrying parts, on which grounding must be applied to protect people from electric shock, was checked;

grounding is applied (grounding knives are turned on, and where they are absent, portable grounding devices are installed);

The causes of electrical accidents are many and varied. The main ones are:

1) accidental contact with open live parts under voltage. This can occur, for example, during the production of any work near or directly on live parts: in the event of a malfunction of protective equipment, through which the victim touched live parts; when carrying long metal objects on the shoulder, which can accidentally touch uninsulated electrical wires located at an accessible height in this case;

2) the appearance of voltage on the metal parts of electrical equipment (housings, casings, fences, etc.), which in normal conditions are not energized. Most often, this can occur due to damage to the insulation of cables, wires or windings of electrical machines and apparatus, which, as a rule, leads to a short circuit to the case;

3) an electric arc that can form in electrical installations with a voltage of more than 1000 V between a live part and a person, provided that the person is in close proximity to the live parts;

4) the occurrence of a step voltage on the earth's surface when the wire is shorted to the ground or when current drains from the ground electrode into the ground (in the event of a breakdown to the body of grounded electrical equipment);

5) other reasons, which include such as: uncoordinated and erroneous actions of personnel, leaving electrical installations energized without supervision, admission to repair work on disconnected equipment without first checking for a lack of voltage and a malfunction of the grounding device, etc.

The main measures to eliminate the causes of electric shock discussed above and ensure the protection of operating personnel are:

* Ensuring the inadmissibility of current-carrying parts under voltage for accidental contact. For this purpose, current-carrying parts must be located at an inaccessible height; fencing and insulation of live parts are widely used;

* application of protective grounding and grounding of electrical installations;

* automatic shutdown, undervoltage application, double insulation and etc.;

* the use of special protective equipment - portable devices and devices, means personal protection;

* clear organization safe operation electrical installations.

End of work -

This topic belongs to:

Life safety

Ministry of Education and Science of the Russian Federation. Federal State Budgetary Educational Institution of Higher vocational education samara state aerospace

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Statistics show that electric shocks are commonly found in the home and at work. How to protect yourself and what to do in case of exposure to current?

What is an electrical injury?

Cases of electric shock are rare, but at the same time they are among the most dangerous injuries. With such a lesion, a fatal outcome is possible - statistics show that it occurs on average in 10% of injuries. This phenomenon is associated with the effect of electric current on the body. Therefore, representatives of professions related to electricians can be attributed to the risk group, but they are not excluded among people who accidentally encountered the action of current in everyday life or on sections of power lines. As a rule, the cause of such a defeat is technical problems or non-compliance with safety regulations.

Types of electric shock

The nature of the impact on the body and its degree can be different. The classification of the lesion is based precisely on these features.

Electrical burn

Electric shock is one of the most common injuries. There are several variants of such an injury. First of all, it should be noted the contact form, when an electric current passes through the body upon contact with a source. An arc lesion is also distinguished, in which the current itself does not pass directly through the body. The pathological effect is associated with an electric arc. If there is a combination of the forms described above, such a lesion is called mixed.

Electrophthalmia

An electric arc leads not only to a burn, but also to irradiation of the eyes (it is a source of UV rays). As a result of such exposure, inflammation of the conjunctiva occurs, the treatment of which can take a long time. In order to avoid such a phenomenon, special protection against electric shock and compliance with the rules for working with its sources are necessary.

Metallization

Among the types of skin lesions, metallization of the skin stands out with its clinical features, which occurs due to the penetration of metal particles melted under the action of an electric current. They are the smallest in size, penetrate into the surface layers of the epithelium of open areas. Pathology is not fatal. Clinical manifestations soon disappear, the skin acquires a physiological color, and pain stops.

electrical signs

Thermal and chemical action leads to the formation of specific signs. They have sharp contours and color from gray to yellowish. The shape of the signs can be oval or round, as well as resemble lines and dots. The skin in this area is characterized by the occurrence of necrosis. It becomes hardened due to the necrosis of the surface layers. Due to cell death in the post-traumatic period, there are no complaints among complaints. The lesions disappear after some time due to regeneration processes, while the skin acquires a natural color and elasticity. This type of injury is very common and usually non-fatal.

Mechanical damage

They occur with prolonged exposure to current. Mechanical injuries are characterized by ruptures of muscles and ligaments, which occurs due to muscle tension. In addition, the neurovascular bundle is additionally damaged, and such severe injuries like fractures and complete dislocations. More serious and highly qualified assistance is required in case of electric shock with such a clinic. In case of untimely assistance or too long exposure, a fatal outcome is possible.

As a rule, these types do not occur separately, but are combined. This factor makes it difficult to provide first aid and further treatment.

What determines the degree of electric shock?

This indicator depends not only on the strength, duration of action and the nature of the current, but also on the resistance of the body. Skin and bones have high rate resistance, in the liver and spleen, on the contrary, it is low. Fatigue contributes to a decrease in resistance, and therefore, in such cases, a fatal outcome is most likely. Wet skin also contributes to this and clothes and shoes made of leather, silk, wool and rubber will help protect the body from harmful effects, as they will act as an insulator. It is these factors that affect the risk of electric shock.

Consequences

Electrical current causes multiple damage. First of all, it acts on the nervous system, due to which it worsens physical activity and sensitivity. In addition, there are, for example, severe convulsions and loss of consciousness can cause death due to respiratory arrest. After rescuing the victim, deep lesions of the central nervous system. The main ones lead to this.

Impact on the heart can also lead to death, as the current leads to impaired contractility and causes fibrillation. Cardiomyocytes begin to work inconsistently, as a result of which the pumping function is lost, and the tissues do not receive the necessary amount of oxygen from the blood. This leads to the development of hypoxia. Another formidable complication is rupture of blood vessels, which can lead to death from blood loss.

Muscle contraction often reaches such a force that a fracture of the spine is possible, and, consequently, damage to the spinal cord. On the part of the sense organs, there is a violation of tactile sensitivity, tinnitus, hearing loss, damage to the eardrum and elements of the middle ear.

Complications do not always appear immediately. Even with a short exposure, electrical injury can make itself felt in the future. Long-term effects - arrhythmias, endarteritis, atherosclerosis. From the side of the nervous system, neuritis, vegetative pathologies and encephalopathy can occur. In addition, contractures are possible. That is why means of protection against electric shock are important.

Causes

The main etiological factor is the action of the current. Additional terms are the state of the body and the presence or absence of any protection. Electrical shock is usually caused by improper use or lack of protection when working with wiring. The risk group includes professions related to working with current. However, electrical injury can happen to anyone. Cases of defeat in everyday life are not uncommon, but they mostly end favorably. In addition, episodes of contact with such lesions are frequent. Attention and knowledge of safety precautions will protect against such phenomena.

Clinical manifestations of electrical injury

Symptoms depend on the type of lesion, while their complex is based on a combination of manifestations of the described types of injuries. Also, the clinic depends on the severity. It should be noted that the most dangerous functional deviations of the respiratory, nervous and cardiovascular systems. The victim is in severe pain. A characteristic pained expression appears on the face, and skin become pale. Under the action of current, muscle contraction occurs, the duration of which depends on the preservation of their integrity. All this can cause loss of consciousness, and in a more severe case - death. Protecting against electric shock will help prevent this condition.

The effect of current on the body

The changes that occur in the body under the influence of current are associated with the versatility of its effects. It has a thermal effect by converting electrical energy into thermal energy due to tissue resistance. This is due to the formation of burns and marks. Thermal action adversely affects the body, as it inevitably leads to the destruction of tissues.

Electrochemical action mainly affects the circulatory system. This leads to a change in the charge of many molecules, and also sticks together blood cells, thickening the blood and promoting the formation of blood clots.

The biological effect is associated with a violation of organs and systems - the effect on muscle tissue, the respiratory system, and nerve cells.

The multiple effect of the current on the body aggravates the condition of the victim, increasing the risk of death. The combined factors of electric shock can lead to a different outcome. Even the action of 220 volts on the body will cause irreversible damage.

First aid

All types of electric shock require otherwise a fatal outcome is possible. First of all, it is necessary to stop the effect of current on the victim, that is, turn it off from the circuit. To do this, the rescuer should definitely protect himself with insulating materials and only after that pull the victim away from the source. After you need to call an ambulance team and start providing first aid. These activities are carried out before the arrival of specialists. A person exposed to current does not tolerate cold, so it must be transferred to a warm, dry surface. First aid is aimed at restoring vital functions - breathing and blood circulation. This requires cardiopulmonary resuscitation. Every person should be trained in it or have at least the slightest idea. Resuscitation is carried out on a hard surface. The rescuer combines artificial respiration and cardiac massage. It is required to observe the ratio - 2 breaths and 30 clicks. Salvation begins with a massage, since the restoration of blood circulation is a priority. It is performed with straight arms, putting the palms on top of each other (pressure is applied to the area of ​​the wrist on lower part sternum). The recommended frequency is 100 compressions per minute (the chest should move 5 cm). After the oral cavity is cleaned of secretions and artificial respiration is carried out. To protect the rescuer, it is recommended to manipulate through a handkerchief. Resuscitation can be carried out by two rescuers, while maintaining the ratio of 2 breaths and 15 clicks. When one person takes a breath, the second is contraindicated to touch the chest. When inhaling, the chest of the victim must necessarily rise - this indicates the correctness of the procedure.

Treatment

Electric shock requires prompt resuscitation and subsequent treatment. The therapy is carried out in a hospital. Even if the victim feels satisfactory, and the damage is minor, preventive monitoring is required to help avoid complications.

Treatment is aimed at the speedy healing of skin lesions, as well as the elimination of other disorders associated with the harmful effects of current. Observation in the hospital is carried out until complete recovery.

Prevention

To prevent all types of electric shock will help compliance with safety regulations. Do not use electrical appliances that are defective. It is also contraindicated to touch them with wet hands, as this will improve the conduction of current. Working with electrical appliances and wiring requires the use of protective equipment against electric shock. These include gloves, special pads. Tools must have an insulated handle. Also, for prevention, the public should be informed about the possibility of such an injury. A special role is played by informing in the media, as well as conducting conversations with schoolchildren. This will reduce the risk of electric shock.

Electrical injuries are very dangerous, and their outcome depends on many factors. It is influenced not only by current indicators (voltage, duration), but also by the body's defenses. For example, a current of 220 volts, depending on the conditions of exposure, can lead to both non-fatal injuries and death. It is very important to observe safety precautions - this will help to avoid such defeats.

The type and frequency of the current also affect the degree of damage. The most dangerous is alternating current with a frequency of 20 to 1000 Hz. Alternating current is more dangerous than direct current, but this is typical only for voltages up to 250-300 V; at higher voltages it becomes more dangerous D.C.. Up-Frequency alternating current passing through the human body, the impedance of the body decreases, and the passing current increases. However, a decrease in resistance is possible only within frequencies from 0 to 50-60 Hz. A further increase in the frequency of the current is accompanied by a decrease in the danger of damage, which completely disappears at a frequency of 450-500 kHz. But these currents can cause burns both when an electric arc occurs, and when they pass directly through the human body. The decrease in the risk of electric shock with increasing frequency is practically noticeable at a frequency of 1000-2000 Hz.

Individual properties of a person and condition environment also have a significant effect on the severity of the injury.

Conditions and causes of electric shock

The defeat of a person by electric current or electric arc can occur in the following cases:

when a single-phase (single) touch of a person isolated from the ground to uninsulated live parts of electrical installations under voltage;

when a person simultaneously touches two non-insulated parts of electrical installations that are energized;

when approaching a person who is not isolated from the ground, at a dangerous distance to current-carrying parts of electrical installations that are not protected by insulation, which are energized;

when a person who is not isolated from the ground touches non-current-carrying metal parts (cases) of electrical installations that are energized due to a short circuit on the case;

under the action of atmospheric electricity during a lightning discharge;

As a result of the action of an electric arc;

when releasing another person who is under tension.

The following causes of electrical injuries can be distinguished:

Technical reasons - non-compliance of electrical installations, protective equipment and devices with safety requirements and conditions of use, associated with defects in design documentation, manufacturing, installation and repair; malfunctions of installations, protective equipment and devices that occur during operation.

Organizational and technical reasons - non-compliance with technical safety measures at the stage of operation (maintenance) of electrical installations; untimely replacement of faulty or obsolete equipment and the use of installations that have not been put into operation in the prescribed manner (including home-made ones).

Organizational reasons - non-fulfillment or incorrect fulfillment of organizational security measures, inconsistency of the work performed with the task.

Organizational and social reasons:

work overtime (including work to eliminate the consequences of accidents);

inconsistency of the work of the specialty;

Violation of labor discipline;

· admission to work on electrical installations of persons under 18 years of age;

attraction to work of persons who have not been issued an order for employment in the organization;

admission to work of persons with medical contraindications.

When considering the causes, it is necessary to take into account the so-called human factors. These include both psychophysiological, personal factors (a person’s lack of individual qualities necessary for this work, a violation of his psychological state, etc.), and socio-psychological (unsatisfactory psychological climate in the team, living conditions, etc.).

Measures for protection against electric shock

According to the requirements of regulatory documents, the safety of electrical installations is ensured by the following main measures:

1) inaccessibility of live parts;

2) proper, and in some cases increased (double) insulation;

3) grounding or grounding of electrical equipment cases and elements of electrical installations that may be energized;

4) reliable and fast automatic protective shutdown;

5) the use of low voltages (42 V and below) to power portable current collectors;

6) protective separation of circuits;

7) blocking, warning signaling, inscriptions and posters;

8) the use of protective equipment and devices;

9) carrying out scheduled preventive repairs and preventive testing of electrical equipment, apparatus and networks in operation;

10) carrying out a number of organizational activities (special training, certification and re-certification of electrical personnel, briefings, etc.).

To ensure electrical safety at the enterprises of the meat and dairy industry, the following are used: technical ways and protective equipment: protective grounding, grounding, low voltage application, winding insulation control, personal protective equipment and safety devices, protective shutdown devices.

Protective earth is an intentional electrical connection to earth or its equivalent to non-current-carrying metal parts that may be energized. It protects against electric shock when touching the metal cases of the equipment, the metal structures of the electrical installation, which, due to the violation of electrical insulation, are energized.

The essence of protection lies in the fact that during a short circuit, the current passes through both parallel branches and is distributed between them in inverse proportion to their resistances. Since the resistance of the person-to-ground circuit is many times greater than the resistance of the body-to-ground circuit, the current flowing through the person is reduced.

Depending on the location of the grounding conductor relative to the equipment to be grounded, remote and contour grounding devices are distinguished.

Remote grounding switches are located at some distance from the equipment, while the grounded enclosures of electrical installations are on the ground with zero potential, and a person, touching the enclosure, is under the full voltage of the grounding conductor.

Loop ground electrodes are placed along the contour around the equipment in close proximity, so the equipment is located in the current spreading zone. In this case, when shorting to the housing, the ground potential on the territory of the electrical installation (for example, a substation) acquires values ​​close to the potential of the ground electrode and grounded electrical equipment, and the contact voltage decreases.

Zeroing is a deliberate electrical connection with zero protective conductor metal non-current-carrying parts that may be energized. With such an electrical connection, if it is reliably made, any short circuit to the body turns into a single-phase short circuit (i.e. a short circuit between the phases and the neutral wire). In this case, a current of such strength arises at which the protection (fuse or circuit breaker) is activated and the damaged installation is automatically disconnected from the mains.

The causes of electrical accidents are many and varied. The main ones are:

1) accidental contact with open live parts under voltage. This can occur, for example, during the production of any work near or directly on live parts: in the event of a malfunction of protective equipment, through which the victim touched live parts; when carrying long metal objects on the shoulder, which can accidentally touch uninsulated electrical wires located at an accessible height in this case;

2) the appearance of voltage on the metal parts of electrical equipment (housings, casings, fences, etc.), which are not energized under normal conditions. Most often, this can occur due to damage to the insulation of cables, wires or windings of electrical machines and apparatus, which, as a rule, leads to a short circuit to the case;

3) the appearance of voltage on the disconnected current-carrying parts as a result of the erroneous switching on of the disconnected installation; short circuits between disconnected and energized live parts; lightning discharge into the electrical installation and other reasons

4) an electric arc that can form in electrical installations with a voltage of more than 1000 V between the current-carrying part and a person, provided that the person is in close proximity to the current-carrying parts;

5) the occurrence of a step voltage on the earth's surface when the wire is shorted to the ground or when current drains from the ground electrode into the ground (in the event of a breakdown on the body of grounded electrical equipment);

6) other reasons, which include such as: uncoordinated and erroneous actions of personnel, leaving electrical installations energized without supervision, admission to repair work on disconnected equipment without first checking for a lack of voltage and a malfunction of the grounding device, etc.

All cases of electric shock to a person as a result of an electric shock are possible only when the electrical circuit is closed through the human body, that is, when a person touches at least two points of the circuit between which there is some voltage.

The voltage between two points in the current circuit, which are simultaneously touched by a person, is called the touch voltage.

A touch voltage of 20 V is considered safe in dry rooms, because the current passing through the human body will be below the threshold non-letting one and the person who received an electric shock will immediately tear his hands off the metal parts of the equipment.

In damp rooms, a voltage of 12 V is considered safe.

The step voltage is the voltage between the points of the earth, due to the spreading of the fault current to the ground while simultaneously touching the person's legs. The greatest electrical potential will be at the point of contact of the conductor with the ground. As we move away from this place, the potential of the ground surface decreases and at a distance approximately equal to 20 m, it can be taken equal to zero. Damage during step voltage is aggravated by the fact that due to convulsive contractions of the muscles of the legs, a person can fall, after which the current circuit closes on the body through the vital organs.