Voltage drops in the mains, causes and methods of protection. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Voltage drops in the mains, causes and methods of protection. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Protection of equipment from emergency operation of the network

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Introduction

Mains voltage fluctuations have existed for a long time, but recently this problem has become more and more relevant for our country. This is due to the constant increase in electricity consumption.

If until the 90s all household appliances consisted of a TV, refrigerator and tape recorder, now every apartment has a lot of powerful and at the same time sensitive household appliances (computers, air conditioners, freezers, microwave ovens, washing machines, video and audio equipment, etc.). which is connected to the network almost all the time.

The result of a voltage drop in the mains may be the failure of a part of household appliances installed in the apartment and connected to the network at that moment. In the vast majority of cases, the reason for the failure of household appliances is an overvoltage in the network.

After consumer appliances burn down, people start asking questions:

How could this happen? What is the reason? How to avoid? And perhaps the main question: Who is to blame?

In the following, I will try to answer most of the questions in an accessible way.

Why do surges occur in the network

There are several reasons. Let's highlight the most common:

1. Let's start with the fact that not only you alone (your apartment or house) are connected to the AC power supply, but many consumers like you, which is important, and many more industrial and construction facilities. It would seem, what impact can one house have on the power grid? Definitely a minor impact.

And if, at the same time as you, a thousand consumers turn off their equipment, especially high-power ones (electric kettles, water heaters, microwave ovens, air conditioners, washing machines), then we get a kind of overvoltage, you all noticed voltage drops in the evenings, this is noticeable by incandescent lamps.

But do not be afraid, it will still be less than the permissible GOST and all your equipment will continue to work in normal mode.

Another thing is that if an entire plant or construction site is turned on / off at the same time. Imagine what a "jump" voltage will happen!

This option is possible in areas where the infrastructure is associated with a large factory or large construction. Then it is possible that your equipment will fail.

Voltage drops in the mains, causes and methods of protection
Fig. 1

2. The most common reason for the residential sector is breaks in the neutral wire.

You all know the deplorable state of electrical transformer substations, input devices to the building and storey switchboard entrances, most often due to the lack of a serving electrician or his illiteracy.

Periodically, it is necessary to carry out preventive repairs in electrical switchboards, which, in principle, is not done, therefore, over time, bolted connections weaken, the reliability of electrical contact deteriorates, which can lead to burnout of the supply wires.

Much more often, the zero working conductor (N) burns out, which leads to the appearance in your outlet group of a voltage above the permissible level due to uneven power consumption.

The diagrams show that during normal operation, the voltage between the phases (L1, L2, L3) and the zero working conductor (N) is 220 volts, the current goes from phase to zero, and the voltage between the phases is 380 volts.

At the moment of breakage of the zero working conductor (N), the current will flow between the phases, i.e. there will be an overvoltage in the sockets in the range of 220-380 volts, it depends on the power of the electrical appliances connected at that moment.

3. The reason is a purely human factor, or rather the illiteracy of an electrician or the self-confidence of a home master.

The lights went out at home, one of the most common causes phase wire burnout (L1, L2, L3) or zero working conductor (N), You yourself or, having called an electrician, restore the power supply, when connecting, you mixed up the wires by connecting instead of 220V (phase-zero), a voltage of 380V (two phases), perhaps not even to yourself, but to your neighbors on the floor.

Result, instant failure of all electrical equipment connected to the mains.

4. Last but not least are power surges caused by lightning strikes near power lines (power lines).

Very dangerous, I strongly recommend if you do not have special equipment for surge protection, turn off household appliances from the network during a thunderstorm.

Harm of low mains voltage

A situation is possible when the voltage in the network is greatly underestimated. What is often found at the facilities of the old building due to the inability of the old wires to deliver the necessary power, as well as the switching by utilities, on purpose, of all the apartments of the riser to the phase of the same name, due to the fear of burning off the zero working conductor, which would lead to overvoltage in the network. Reduced mains voltage can damage some household appliances or their functions, for example, a microwave oven rotates a plate, but does not heat up; the washing machine runs non-stop; The most common failure is the failure of the refrigerator compressor, due to the constant on position, even when you are not at home.

Damage to equipment from undervoltage is less common than from overvoltage. You can also avoid equipment failure by using the points from the section "How to deal with overvoltage in the network"

And so we examined the main causes of voltage drops in the power grid, but it’s easier not to get because the equipment has already burned out, then read on.

Who is responsible for the lost household appliances

Paradoxically, despite the fact that the electricity supplier undertakes to provide you with voltage of the established quality, most likely you will not be able to receive compensation for the lost equipment.

This is due to the following considerations.

How can you prove that the reason for the failure of the equipment is an overvoltage in the network, and not a defect in the equipment.

The lack of real control and collection of statistics leads us to the following conclusion. In 99% of cases, you will not be able to receive compensation for lost equipment. it is impossible to prove whose fault this is, as we said earlier, there are many causes of overvoltage, both related to the human factor and force majeure by definition (lightning discharge near power lines).

What to do, is it really every time to throw out the equipment? Of course not. There are methods to deal with power surges.

How to deal with overvoltage in the network?

There are several ways:

1. Reconstruction of electrical networks and maintenance by competent electrical personnel, a very expensive option and only reduces the risk of overvoltage, most often depends on utilities.

2. The use of voltage stabilizers is ideal for those who use very expensive equipment. You connect the network wires to the stabilizer and already remove high-quality voltage from it. The option is very good - there is only one minus - this is the price. The price of a good (quality) stabilizer with a power of 5 kW is over 500 USD. Accordingly, if you have a large amount of equipment, you will have to spend a tidy sum, but after that (with the right choice of stabilizer), you can be sure that your equipment is reliably protected.

3. If you work with valuable information on a computer, then choose an uninterruptible power supply (UPS), which is most often used in administrative buildings, but you can’t install an uninterruptible power supply only for office equipment, for all household appliances because of the high price.

4. Voltage limiting relays are the most affordable option for protection against voltage surges in the mains.

Publication: electro.narod.ru

See other articles Section Protection of equipment from emergency operation of the network.

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