Safety rules near a broken wire of an overhead power line. Safety rules near a broken wire of an overhead line What protective equipment must be used when servicing electrical installations

Everyone knows that if there is a break in the high-voltage network in front of him, and the wire lies on the ground, then this can be dangerous. In fact, this statement only applies to power lines with a voltage of up to 25 kV, since they are switched off only after a break is detected. If the network has a voltage of 110 kV or more, after the wire breaks and falls to the ground, its power is immediately turned off automatically.

But an ordinary person is unlikely to know about this and will not be able to recognize which network is in front of him, so in any case, you need to follow the safety rules when a break is detected.

What is step voltage

Step voltage is the main danger for a person who is close to a power line that has fallen to the ground. From the place where the wire touches the ground, the electric current begins to spread along the ground, gradually weakening, at a distance of at least 8 meters. In this case, a potential difference arises between the points of the earth spaced apart from one another. If a person walks and touches the ground at two points, an electric current caused by this potential difference begins to flow through his body, representing a mortal danger. This voltage is called step voltage. A wire that does not touch the ground, but falls on a tree, car or building, is no less dangerous: in this case, the step voltage zone can be increased.

The basic rule for avoiding step voltage is to avoid touching the ground at two points at the same time. You can only move with a “goose step”, without taking your legs one from the other and without touching any objects or people that are in the affected area.

In principle, one can move by jumping on one leg or two legs connected together, or running, then only one leg touches the ground at any given time. But this method is more risky, since there is a risk of tripping, falling on your hands, while falling under the influence of step voltage. Therefore, the "goose step" is the safest way to leave the danger zone.

If a person is under stress, what should I do?

First of all, it is necessary to take measures to turn off the broken network by informing the dispatcher on duty about the accident. If this is not possible, the person must be removed from the effects of electric current as soon as possible. You can approach it exclusively with a “goose step”, after which you can drag it beyond the limits of the step voltage. If the wire touches the human body, it can only be thrown aside with a dry stick.

If we are talking about a team of electricians who performed repair work, then they, as a rule, have dielectric shoes that allow you to move around the wire safely. Such crews usually have radio contact with the dispatcher, who can be informed of the need to turn off high-voltage equipment. After pulling a person out of the danger zone, it is necessary to call doctors to assist him and transport him to the hospital.

Danger of sagging wires

An electric wire sagging from a power line pole for various reasons can be dangerous to a person, even if it does not touch the ground. So, if the network has a voltage of 110 kV, a person who is at a distance of less than one meter from a sagging wire can be struck by a current, therefore it is strictly forbidden to approach it.

One of the most common emergencies in electrical networks is a wire break in an overhead power line. As a rule, power lines of those electrical networks that operate in the isolated neutral mode, in which a single-phase ground fault - that is, a wire falling to the ground, do not lead to a line blackout, pose a great danger.

Such lines after a wire fall may be in operation for some time until damage is detected. These are high-voltage lines with a voltage of 6, 10, 35 kV.

In electrical networks with a voltage of 110 kV and above, any earth fault is an emergency mode and is usually turned off by high-speed protections. That is, when a wire falls to the ground in these electrical networks, the line is de-energized in a fraction of a second. But, as a rule, not every person knows how to determine the line voltage class and, accordingly, you need to know how to behave in case of a broken power line wire. Consider the safety rules that should be observed if you are near a broken overhead line wire.

Why is it dangerous to drop a wire to the ground?

To begin with, consider the question of why it is dangerous to drop a wire to the ground. When a live wire falls to the ground or to a conductive surface, fault currents flow. In open areas, currents spread within a radius of eight meters from the point of contact of the wire with the ground. If a person falls within the range of earth fault currents, then he falls under the so-called.

Step voltage- this is the voltage that occurs between two points on the surface, in this case the earth, at a distance of a person's step. That is, if a person in the area of ​​action of earth fault currents takes a step, then he falls under the step voltage.

In order not to fall under the voltage of a step near a broken wire of a power line, several rules must be observed.

The first thing to do is to leave the danger zone, that is, it is necessary to move away from the broken wire at a distance of more than 8 m. You need to move in the area of ​​​​ground fault currents with a “goose step”, without taking your legs off each other. At the same time, it is forbidden to touch any objects and other people located in the danger zone.

Sometimes there are recommendations for moving in the area of ​​current spreading by jumping on closed two or one leg. By itself, this method of moving in the area of ​​spreading of earth fault currents is safe, since in this case the person’s legs are not open, the person touches the ground with one point. But with this method of movement, you can stumble and stand on two legs at a step distance or fall on your hands. In this case, a person falls under the action of step voltage, as it comes into contact with the ground at two points remote from each other. Therefore, it is most safe to move from the zone of spreading of fault currents to the ground with a “goose step”.

For employees of electrical installations, it is important to know that the spreading of fault currents also occurs indoors. In this case, when a live wire falls, the currents spread to a distance of up to four meters from the point of contact of the wire with the floor or conductive surface.

Free movement in the zone of spreading of short circuit currents, both indoors and outside, is possible only with the use of specialized electrical protective equipment - dielectric boots or dielectric galoshes.

In the event of a wire break in places where people may appear, before the damaged line is de-energized, it is necessary to warn people approaching the place where the wire fell about the possible danger of electric shock.

Rules of conduct upon detection of a person struck by electric shock from a broken wire

Separately, it is necessary to consider the actions in case of detection of a person who is under voltage. First of all, it should be remembered that before the voltage is removed from the damaged line, without protective equipment, it is impossible to approach a person who has fallen under the action of voltage. That is, it is necessary to de-energize the section of the electrical installation or electrical network in which the person was energized. If this cannot be done quickly, then it is necessary to free the person from the action of electric current or electric arc. The safety rules are as follows.

If an accident occurred in a team of power engineers performing repair work, then, as a rule, the necessary protective equipment is available - dielectric gloves, dielectric boots, a protective helmet and overalls. In this case, the release of a person who has fallen under voltage is carried out using the listed protective equipment.

Also, the brigade of power engineers should have communication with higher personnel, the duty dispatcher of electrical networks. Therefore, in the event of an electric shock to a person as a result of approaching a broken power line wire, it is necessary to contact the dispatcher on duty to take measures to relieve voltage from the damaged power line.

In the absence of, approaching a person who has received an electric shock is possible only with a “goose step”. The main task is to free a person from the action of electric current. If a person falls under the action of step voltage, he must be pulled out of the dangerous zone of current spreading. If a person gets voltage as a result of direct contact with the wire, then the wire should be thrown aside before transporting the victim. It is forbidden to touch the wire with your hands; to move the wire, you must first find a dry stick.

After the person is released from the action of the electric current, he needs to provide first aid and call an ambulance to transport the victim to the hospital.

It should be noted that in addition to broken wires, excessively sagging power line wires also pose a danger. Sagging of the wire may occur due to its unreliable fastening, the jumping off of the insulator from the traverse of the support. In this case, there is a high probability of the wire falling to the ground or directly on a person under the power line. If this is a high-voltage power line, then excessive sagging of the bare wire can lead to electric shock to a person, provided that a person is near the wire at an unacceptable distance.

For each voltage value, there is a value for the minimum allowable distance at which a person can be near a wire or other part of an electrical installation that is under operating voltage. For example, for a 110 kV line wire, the safe distance is 1 m, if a person is at a closer distance to the wire, he will be shocked.

Also, wires that do not directly touch the ground, but come into contact with other elements - trees, cars, building structures, etc., are of great danger. In this case, the distance over which the earth fault currents spread can be much more than eight meters.

/ - frame; 2 - devices for protection against short circuit currents (fuses, automatic devices, etc.); Yao ~ grounding resistance of the neutral protective conductor; /s - short circuit current; O - zero protective conductor

In a three-phase four-wire network, the fourth conductor connected to the neutral of the power source and used in the power supply circuit of power consumers is called the neutral working conductor. At the same time, it can also perform the function of a zero protective conductor.

The conductivity of the main neutral protective conductor (connected to the neutral of the power source) must be at least 50% of the conductivity of the phase conductors. This ensures its resistance to heating during the passage of a single-phase short circuit current.

The total resistance of the zero protective conductor, taking into account its inductance, must meet the condition

The zeroing calculation consists in choosing a zero protective conductor (material, cross section, laying method) and then determining the single-phase short-circuit current according to (10.15).

/ - housing: 2 - devices for protection against short-circuit currents. (fuses, circuit breakers, etc.): g "- grounding resistance of the neutral of the current source; gp-resistance of re-grounding of the zero protective conductor; "k-short-circuit current: / „- part of the short-circuit current flowing through the neutral wire. nnl: 13- part of the short-circuit current, leakage, bale I through the ground.

From fig. 6-1 it can be seen that the grounding circuit requires the presence of a zero protective conductor in the network, dead grounding of the neutral of the current source and re-grounding of the neutral protective conductor.

a) Purpose of the neutral protective conductor

Let we have a circuit without a zero protective conductor, the role of which is played by the earth (Fig. 6-2). Will such a scheme work?

Rice. 6-2. On the question of the need for a zero protective conductor in a network up to 1000 V with a grounded neutral.

To eliminate this danger, it is necessary to ensure automatic shutdown of the installation, that is, to increase the current passing through the protection, which is achieved by reducing the resistance of the circuit by introducing a zero protective conductor into the circuit.
After finishing work with liquid and gaseous oxygen or liquid enriched with oxygen, as well as after performing other work in which clothing is saturated with oxygen, it is forbidden to approach the fire or smoke.

If there is a need for a mechanized development of an underwater trench, then the diver is prohibited from approaching the working parts of the machines (receiving end of the suction hose, excavator bucket, etc.) at a distance

3) it is forbidden to approach at a distance of less than 8 m to the energized reinforced concrete supports of the 6-35 kV overhead line if there are signs of a ground fault current flowing through them.

When inspecting electrical installations, it is forbidden to approach current-carrying parts at distances less than those indicated in Table. 12.1.

If a ground fault is detected in any current-carrying part of the electrical installation above 1000 V, before it is turned off, it is forbidden to approach the place of the fault at a distance of less than 4 m in closed and 8 m in open switchgears.

If a broken overhead line wire above 1000 V is found lying on the ground, it is forbidden to approach it at a distance of less than 8 m due to the danger of electric shock due to high step voltages. Near this wire, guards should be organized to prevent people and animals from approaching it, if possible, warning posters should be installed, the incident should be reported to the power grid company and wait for the arrival of the repair team.

If signs of current draining into the ground along a reinforced concrete pole are detected, which is possible on a 3-35 kV overhead line due to damage to insulators, touching the body of the pole with a wire, etc. into the ground, etc.), it is forbidden to approach the pole closer than 8 m. In this case, measures must also be taken to prevent people and animals from approaching the energized pole at a dangerous distance.

On the overhead line at the work site, all wires of the line, and, if necessary, lightning protection cables, isolated from the support *, must be grounded. However, on overhead lines of 35 kV and above, when performing work on the wire of one phase or alternately on the wires of each phase, it is allowed to ground at the workplace the wire of only the phase on which the work is performed. In this case, it is forbidden to approach the wires of the remaining, ungrounded phases at distances less than those indicated in Table. 12.1.

familiarize the team with the content of the order or order, indicate the boundaries of the workplace, show the equipment closest to the workplace and current-carrying parts of the repaired and neighboring connections, which are forbidden to approach, regardless of whether they are energized or not;

BP-1-6. When a ground fault is detected, it is forbidden to approach the fault location at a distance of less than 4-5 m in closed and less than 8-10 m in open switchgears.

Until the contact network is de-energized and grounded, it is forbidden to approach the contact wires at a distance of less than 2 m, and closer than 10 m to the dangling ends. mains, provided that the jet of foam and water does not touch live parts.

Table 1.1 Permissible distances to live parts under voltage

1.3.4. A sole inspection of electrical installations, the electrical part of technological equipment can be performed by an employee with a group of at least III, from among the operational personnel serving this electrical installation during working hours or on duty, or by an employee from among the administrative and technical personnel, having group V, for electrical installations with voltage above 1000 V, and an employee with group IV - for electrical installations with voltage up to 1000 V and the right to a sole inspection on the basis of a written order of the head of the organization.

with admission according to an admission permit - admitting from among the operational personnel, the responsible manager and the foreman, observing - from the premises in which you have to work.

Keys must be returned daily after inspection or work.

When working in electrical installations that do not have local operational personnel, the keys must be returned no later than the next working day after the inspection or complete completion of work.