What are dangerous overloads in the electrical network for a person. Major electrical faults. What to do if the light is out

An overload is a phenomenon when electrical wires and electrical appliances more current flows. The danger of overload is due to the thermal effect of the current. With a double or greater overload, the combustible insulation of the conductors ignites. With small overloads, the insulation ages rapidly and its life dielectric properties is shrinking.

So, overloading wires by 25% reduces their service life to about 3-5 months instead of 20 years, and overloading by 50% renders wires unusable within a few hours.

The main reasons for overload are:

• discrepancy between the cross-section of conductors and the operating current (for example, when wiring to the bell is carried out by a telephone wire);
• parallel connection to the network of current collectors not provided for by the calculation without increasing the cross section of the conductors (for example, connecting an extension cord with 3-4 sockets to one working one);
• contact with conductors of leakage currents, lightning;
• increase in ambient temperature.

In addition, when the electrical network is overloaded, the devices and devices connected to it constantly experience a shortage of current, which can lead to their emergency failure. In this regard, pay attention to the passport data of electrical appliances: current and voltage. It is desirable that the supply voltage of electrical appliances deviate by the maximum allowable value from 220 V (for example, from 90 to 260 V).

A short circuit is any short circuit between wires, or between a wire and ground. The cause of a short circuit is a violation of the insulation in electrical wires and cables, which is caused by: overvoltages; insulation aging; mechanical damage to the insulation.

Transitional resistance is the resistance that occurs at the points of current transition from one wire to another or from a wire to any electrical device in the presence of poor contact at the joints and terminations (when twisting, for example). During the passage of current in such places, per unit time, a large number of warmth. If heated contacts come into contact with combustible materials, then they may ignite, and in the presence of explosive mixtures, an explosion. This is the danger of the substation, which is aggravated by the fact that places with the presence of transient resistances are difficult to detect, and the protective devices of networks and installations, even correctly selected ones, cannot prevent the occurrence of a fire, since electricity in the circuit does not increase, and the heating of the section with the PS occurs only due to an increase in resistance.

Sparking and electric arc - the result of the passage of current through the air. Sparking is observed when electrical circuits are opened under load (for example, when an electrical plug is removed from an electrical outlet), when there is a breakdown of insulation between conductors, and also in all cases when there are poor contacts at the junctions and terminations of wires and cables. Under the action of an electric field, the air between the contacts is ionized and, with a sufficient voltage, a discharge occurs, accompanied by air glow and crackling (glow discharge). With an increase in voltage, the glow discharge turns into a spark discharge, and with sufficient power, the spark discharge can be in the form of an electric arc. Sparks and electric arcs in the presence of combustible substances or explosive mixtures in the room can cause a fire and explosion.

With a metal conductor wire, with ideal conditions exploitation, it may be true that nothing will be done. However, in real conditions, the conductor is subject to oxidation, deterioration of contact and heating at the place of poor contact ... In addition, poor contacts are also formed due to loosening of the screw connections of the wires.

But with the insulation of wires - even more difficult. The aging of the insulation causes the wire to fail and can be accompanied by various troubles - from a short circuit to a fire.

What is the aging of electrical wiring insulation?

First of all, in reducing the elasticity and mechanical strength of its material. The insulation becomes brittle and brittle. A small impact is enough, and its integrity is violated. After that, an electrical breakdown of the insulation and a short circuit may occur. And despite the fact that earlier, mainly combustible materials were used as insulating materials, then in case of emergency heating of conductive conductors of wires and the presence of a fire hazardous environment, a fire occurs.

Causes of aging of electrical wiring insulation

One of the main reasons premature aging insulation is thermal aging caused by an increase in the temperature of the conductor. Naturally, the wire heats up for a reason, but during overloads of the electrical network caused by a prolonged excess of the current allowed for a given section of the conductor. Moreover, the service life of the insulation with an increase in the temperature of the conductor from normal by only 8 degrees - decreases by 2 times!

Causes of electrical overload

There are several reasons for the occurrence of an overload of the electrical network and wiring, among which are:
- incorrect calculation of the conductor section;

Connection of additional consumers, the power of which exceeds the permissible design values;

Mechanical overloads on the shaft of electric motors household electrical appliances;

Long-term deviations of the mains voltage from the nominal value.

Insufficient electrical power supplied to the internal electrical network.

How to avoid electrical overload?

If a mistake was made during the calculation or installation of the electrical wiring and the conductor cross-section is less than required, then the situation can be corrected only by completely replacing such wiring or laying new lines from the electrical panel to the most loaded sockets with a wire of the required cross-section.

The operation of additional energy-intensive consumers, the total consumed current of which exceeds the value of the current setting of the introductory circuit breaker, can only be carried out using automation devices, for example, the OEL-820 power grid load optimizer.

It is necessary to exclude the operation of motors with mechanical overload of the shaft. For example, put a strainer on the suction pipe of a submersible pump so that sand does not get into it, clean the vacuum cleaner bag from dust in time, do not overload the mixer, meat grinder, electric drill, etc.

If the voltage in the house is below or above normal, you need to use a voltage stabilizer. However, it should be borne in mind that when the input voltage is low, the stabilizer increases it at the output by increasing the current consumption, which can also lead to wiring overload.

In case of insufficient allocated or supplied power, the missing kilowatts should be purchased from power engineers by making appropriate changes to the contract and project.

The most budgetary and easiest solution is a “virtual” increase in power grid capacity without purchasing additional power. Those. application of a device for limiting power consumption by controlling a non-priority load. For domestic use The OEL-820 Grid Load Optimizer is the best choice. This is the only household appliance on the market designed to effectively reduce power consumption and connect without the help of a specialist. Plugged it in and forgot about the problem!

Speaking about overloading the electrical network, it should be noted that overloading leads not only to minor malfunctions, such as flashing lights, malfunctions of electrical appliances. Due to network overload, wires and cables heat up, which, if the protection is not properly made, can lead to fire, damage and malfunctions of electrical appliances. As a result, unscheduled repair of TVs or repair of refrigerators and other household appliances that are constantly connected to the power grid. Let's analyze the main causes of network congestion and how to fix this problem.

Power grid overload - main causes

The main causes of electrical overload are:

• Plugging in a faulty device.

More often, an overload in the mains is not a malfunction. It is rather a miscalculation during the creation and installation. If a large number of sockets were included in one, while the value of the circuit breaker was incorrectly calculated, then overload is inevitable.

For example, there were two sockets in the kitchen. Having decided to increase the number of sockets, the craftsmen did not take care of creating a new group, but mounted several more sockets with a cable. Each individual socket does not overload the circuit, and when several devices are turned on, it leads to an overload.

I want to remind you that during an overload, the power grid does not work instantly, as with short circuit. In, for overload protection, there is a bimetallic plate, the heating of which turns off the emergency circuit. It takes several minutes to heat up the plate and cut off the circuit when overloaded.

Therefore, if your circuit breakers periodically work when household appliances are turned on, then it is quite likely that the power supply network is overloaded and the load is distributed incorrectly or the value of the circuit breaker setting is incorrectly selected.

The complexity of the preliminary calculation of each group of outlets in the apartment created one simple installation rule. Do not “hang” more than 4 sockets on one. With this load distribution, combined with a 3x2.5 mm² copper cable and a 25 Amp circuit breaker, there will never be an overload of the group circuit.

Connecting a faulty device to the network

But overloading the power grid can occur not only with improper load distribution. A faulty electrical appliance may well consume increased current and lead to network overload.

If the circuit breaker is turned off only when the “suspect” device is operating, and the power of the device is not more than 2500W, then the device must be repaired or replaced.

Electricity greatly simplifies human life, but not all people correctly assess the potential danger of electricity. Any electrical network is designed for a certain degree of load. Many people know and understand this, but stubbornly continue to load the network, which often leads to unpleasant consequences.

Excessive load can lead to minor interruptions in the operation of various devices, flickering of light. However, these are mere trifles compared to what can happen in the event of a critical overload - a fire in the room.

There are many reasons why overload occurs. electrical network. For example, this phenomenon may occur due to the fault unskilled workers who carried out various manipulations with the power grid.

- all this in most cases leads to subsequent troubles. It is possible to avoid all this if you seek the help of professional specialists.

However, high-quality installation work of the electrical network is not a guarantee of safety..

The consumer of electricity himself often provokes the occurrence of overloads.. Connecting an unacceptable number of electrical appliances to one group is by far the most common problem.

This is especially true in the houses of the old housing stock., where power grids, as a rule, do not meet modern requirements imposed on them not only by current regulations, but also by the lifestyle of households, tk. more and more powerful electrical appliances appear in operation.

How does network congestion occur in practice?

Consider the option with electrical appliances that are often found in everyday life. For example, there is a socket with two sockets, in which the user of the power grid includes washing machine with a power of 2.5 kilowatts (kW) and an electric kettle with a power of 2.2 kW, the total load is 4.7 kW and the electric current flowing through the wires will be about 22 Amperes (A).

As a result, a power outage occurs, since in most cases the circuit breaker will work in the shield or the plug will burn out, because they are usually rated for a current of 10-16A.

This is where a lot of people make a critical mistake. install a circuit breaker or plug with a large load limit, often it is 25A. The devices work, the machine does not knock out, everyone is happy. BUT! Since the most common electrical wiring in houses is made with a wire that can withstand a current of 19A, and modern sockets are designed for a current of 16A, the insulation of the wires begins to smolder, the socket body melts, which can subsequently result in a fire. More worse situation when such devices are plugged into an outlet through an extension cord or tee, tk. it could lead to a fire sooner.

Malfunctions can also lead to overload., both in electrical appliances and in electrical wiring. During prolonged use, contact connections in the same sockets, automatic machines and junction boxes are relaxed, where the connection is often made by twisting the wires, so even the rated load causes them to heat up, which can lead to fire.

It is also a common phenomenon - the wires in the places of bends break over time, the cross section of the wire decreases, therefore, its throughput which again leads to fire.

Separately I would like to mention uncertified Chinese "consumer goods", which is mostly sold in the markets in the form of tees, splitters, extension cords, carriers, etc., which are generally not recommended to be used. Sometimes even weak Charger For mobile phone causes heat in their contact connections.

I would like to specifically mention about errors in the installation and repair of electrical wiring when unfortunate craftsmen or non-specialists connect the wires simply by twisting, claiming that everyone used to do this and these connections still serve. Yes, in many houses such connections served long years. But before there were no such loads on the electrical network.

Now, buying modern household appliances, which consumes significant power, people, without hesitation, connect it to the existing network and eventually get problems in the form of melted insulation, burning contacts and, worse than that, ignition. So that such problems do not arise, the current rules provide for the connection of wires by crimping, welding, soldering or clamping (screw, bolt, etc.).

To protect the network from overloads, even at the stage of a major overhaul or construction of a new house, it is necessary:

1. Calculate the allowable number of electrical appliances per branch.
2. Decide on the correct location of the devices.
3. Calculate the required wire cross section.
4. Divide the wiring into separate groups.
5. Select protective equipment in accordance with the cross section of the wires and the connected load.

During operation, in order to avoid overloads, it is also necessary to follow a number of rules:

1. Periodically invite qualified specialists to inspect and maintain electrical wiring and contact connections in the switchboard, sockets, switches, junction boxes, and perform the necessary electrophysical measurements.
2. In the event of a tripping of the protective equipment, invite a specialist to find out the reasons and, if necessary, carry out repair work in the electrical network.
3. Timely carry out major repairs of electrical wiring and carry out timely replacement of obsolete elements.
4. Do not plug more than one appliance into the same outlet.
5. Do not use homemade or non-certified electrical appliances and other electrical products.

All work on the design, installation and repair of electrical wiring and electrical equipment must be carried out by qualified specialists who take into account all the nuances and requirements of both current regulations and the customer.

Using these tips, you can ensure stability, reliability and, most importantly, safety in the residential electrical network, prevent overloads, fires and other troubles.

O.V. Semenovich, head of the energy inspection group of the Slutsk MRO Energonadzor

If the current in the mains is higher than the nominal or permissible value in some section of the circuit, then such an unpleasant phenomenon as overload occurs.

Since this can happen in different parts of the circuit, therefore, the consequences can also be different, and you may need the services of an electrician.

This type of overload, as local, occurs in the section of the circuit from the circuit breaker to the consumer. With this type of overload, the safety device is switched off locally.

The so-called local overload implies an overload of the entire line from the step-down transformer to the consumer, as a result of which the voltage in the network decreases. Since at times of strong overloads, the local protection system may fail, as a result of which the protection devices at the substation may operate. As a result, all consumers powered by this transformer are de-energized. In order to avoid failure of the complex Appliances it is advisable to use .

An overload, referred to as general, occurs when the power system is partially or completely overloaded. In such cases, in addition to reducing the voltage, the frequency of the voltage may also decrease. As a result, the protection system at the substation is triggered, which leads to a blackout of the entire system.

A good example of a general congestion is the case in New York, when, due to overload and poor training of dispatchers, a huge number of firms were left without power.

It is also possible to overload the neutral wire, which occurs in three-phase circuits. Such an overload is quite dangerous and unpredictable, since it cannot be detected using switchboards, and fuses are not placed on the neutral wire. The neutral wire in a three-phase circuit has a very significant function. It is needed in order to equalize the voltage in the case of different phase loads. Thus, if the neutral wire breaks, in case of different loads on the phases, the voltages on them will be different, as a result of which the phase with a larger load will have a voltage below normal, even if the overload is still far away. In order to prevent a break in the neutral wire, a fuse is not placed on it. Also, this type of failure is a rather rare case, although the most dangerous, and with proper design and operation of the power grid, it can be completely eliminated.

On the territory of the CIS countries, it is customary to use a four-core cable, which allows you to create an electrical three-phase network with a solidly grounded neutral. The principle of such wiring includes three phase wires, and one neutral, which also performs the function of grounding. Unlike us, in Europe it is customary to use a five-core wire for such purposes, where three wires for phases are also used, one for neutral and one (separate) for grounding.

The problem of networks as a whole, of course, can be solved by using high-quality wiring, but on given time it is very expensive and, therefore, you have to use additional funds protection.