What is overvoltage in the electrical current and what is its danger?

What is a dangerous phenomenon?

Overvoltage in the electrical current is as follows:

Insulation of electrical cables and wires, as well as electrical devices capable of withstanding a certain voltage level specified in the operating documents on them only. The table below shows approximate wattage values ​​for insulation of electrical wires and electrical equipment.

However, in household electrical beds, this is not the main thing (insulation cannot be replaced), but insulation failure resulting from mechanical (including as a result of connecting electrical wires with compression and twisting), climatic (damp, water ingress) and purely economic (accumulation Dust, dirt, insects, etc.). Therefore, overvoltage is also imposed for all such violations.

All this leads, as sad cases show, to the failure of electrical wiring and electrical appliances, to tragic fires. If the electrical protection in the house is also broken (defective or rough with frequent tripping), the probability of a fire as a result of  overloading of wires  or  a short circuit  increases significantly. If a damaged device can simply be unplugged from the outlet and replaced with a working one, then the wiring cannot be quickly replaced. The photo shows damage to the insulation in the outlet, which is often caused by excessive contact and overheating, or as a result of a thunderstorm, which can lead to overload of the wires and short circuit.

Thus, overvoltage in the home electrical network is especially dangerous for old electrical wiring, which is not subject to routine inspection (with outlets) and is not updated, being handled carelessly, allowing it to overheat. The danger should be considered especially dangerous. In this regard old wiring in houses, which are often exposed to thunderstorms and insect invasion (village and town).

As a result of overvoltage, expensive electronic equipment can instantly fail, especially TV and computer, which, as a rule, have no protection against this. Look at the label near the power cord, often 250V is indicated, while the current GOST allows 253V. Therefore, the modern market is maximally saturated with all kinds of stabilizers and various surge protection devices.

Varieties of overvoltage

First of all, it should be noted that overvoltage is divided into four types:

• Atmospheric or thunderstorms;
• switch;
• transitory
• electricity.

Think briefly about the causes of each type of serious condition.

Atmosphere

This type belongs to natural phenomena and is considered the most dangerous, as it is caused by particularly strong lightning discharges. With such discharges, the pulse overvoltage (depending on the location of the lightning branch) can reach tens of thousands of volts per microsecond.

Lightning can reach directly into the power supply network (overhead line) or into the lightning rod (air end). Overvoltage can also be caused by lightning straying away from the electrical current (due to electromagnetic interference).

Impulses can be of different shapes and durations. For example, the figure below shows two typical wave types – 10/350 and 8/20.

It should be noted that in the presence of a lightning rod that protects the body from complete discharge, most of the pulse current is diverted to ground, and the rest is distributed randomly in the household wiring.

Switch

This phenomenon occurs when a shared local area network significantly changes its established way of working. This can occur as a result of a sharp start or stop of powerful equipment, as well as during emergency overloads. There is a so-called transition process, which is oscillatory in nature at a high frequency (up to hundreds of kilohertz). In this case, the overvoltage can be very high. They are determined by the characteristics and parameters of the currently selected network, the distribution of phase loads.

For example, when you turn off a powerful transformer, all the power that is currently in the form of magnetic saturation, can lead to an overvoltage surge in the network and cause instant damage to electrical equipment.

transitory

A similar phenomenon occurs as a result of interruptions and damage in networks. For example, due to the interruption of the common neutral conductor of consumers in a three-phase network, the so-called “zero break”, the stresses in the phases are distributed significantly depending on the phase load (“phase imbalance”). This is the case for transformers not equipped with appropriate compensators.

electricity

This phenomenon occurs in dry air, in materials that retain electrical charge well. A discharge can occur between materials and wires completely unexpectedly, instantly causing overvoltage and damage to equipment connected to the network. Electrostatic potential is invisible and cannot be felt by humans, only the discharge is felt (and many have experienced it).

For example, if you wear insulating shoes, then when walking on a carpet, a person is charged up to several thousand volts. And if you then touch any structure that has conductive properties (for example, a battery or a computer case), an electrical discharge will occur lasting several nanoseconds. Such electrostatic effects are extremely dangerous for electronic parts of any electrical equipment. In the manufacture of electronic equipment, it is strictly required to wear grounding bracelets and use many other protective equipment.

About how to protect yourself from static electricity, tell us in the corresponding article on the site!

Protection measures

The electrical network must always be reliable, comply with the above GOST on the quality of power supply and have protective devices against possible overvoltages (especially in areas with high lightning risk). It is impossible to completely avoid pulse overvoltage, but its value can be reduced to a relatively safe level (modern equipment is manufactured with a certain margin of voltage).

To protect your home’s power supply and appliances, you should:

• Create protection against lightning (if there is nothing nearby) – air terminal;
• Install SPD – a special protective device that reduces dangerous pulse voltages;
• Install in the power board RCD and voltage relay.

More about surge protection devices we said in the corresponding article, which we highly recommend you read!

Important!  You do not know who compensates for damage when electrical appliances burn out? The power supply company bears full responsibility for the quality of voltage in the network. Therefore, in the first place, you should contact him there and write a statement indicating the losses you have caused. However, before this, you should obtain documents proving the causes of damage (acting with witnesses, photos with the date of shooting, control measurements of high or low voltage by calling a competent electrician with a special device). It is necessary to refer to the above GOSTs.

So we examined what overvoltage is in the network, what are the reasons for its occurrence and how to protect ourselves from this phenomenon at home. We hope you find the information provided useful!