Power surges and other electrical problems are not uncommon. They can lead to the failure of expensive equipment and even threaten the life and health of people. To prevent such consequences, there are various electrical network protection devices on the market, which are used depending on the nature of the malfunction.
In this article, you will learn: what are voltage drops and what are their causes; What network protection devices exist and in what cases are they used.
Content
Permissible electricity parameters
In Russia and in the post-Soviet space, the standard voltage is 220 volts (for ordinary electricity consumers).At the same time, in reality, the voltage fluctuates within certain limits from a given nominal value. The permissible amplitude of deviation from the norm is established by the norms and acts regulating the provision of this service to the consumer. At 220V, the minimum allowable value is 198V and the maximum is 242V.
Will traffic jams or machines save?
For a long time, “plugs” were used in homes: fuses that protect against power surges. They were replaced by modern and more convenient automatic machines (circuit breakers). Today, in most apartments, these are the only means of protection against network problems.
Plugs and circuit breakers allow you to protect yourself from short circuits, overheating of wiring and fire during overload. However, a powerful electrical impulse can have time to pass through the machine and disable the equipment. This happens, for example, as a result of a lightning strike. That is, conventional plugs cannot provide full protection against voltage surges.
The main causes of power surges in the network
Power surges may differ in the magnitude of the deviation from the norm, in their duration and the dynamics of increase / decrease, depending on the reasons for their occurrence:
- High load on the network. Simultaneous connection of a large number of electrical appliances with insufficient network power leads to voltage instability. This can be noticeable, for example, as the flickering of light bulbs or the sudden shutdown of electrical appliances. This phenomenon is common, especially in the evenings;
- Powerful consumer next door. It happens if there are industrial facilities, shopping centers, office buildings with a powerful ventilation system nearby, and so on.
- Break of the neutral wire. The neutral wire equalizes the voltage at electricity consumers. When it breaks (combustion, oxidation), some consumers will receive an increased voltage (and others underestimated), which will most likely lead to failure of unprotected electrical engineering.
- Connection errors. For example, if the neutral and phase wires were mixed up;
- Bad wiring. Failures occur due to worn out wiring, the use of low-quality materials and improperly performed installation work.
- Lightning strike. Lightning strikes on power lines can cause rapid voltage spikes of thousands of volts. Represents a particular danger, since the means of protection do not always have time to work.
Possible consequences of power surges
Manufacturers of electrical equipment take into account the unstable nature of the voltage and the possibility of its surges and drops. For example, a device with a nominal voltage of 220 volts can operate at 200V and withstand surges up to 240V. At the same time, regular operation of the equipment with large deviations from the norm reduces its service life. Strong power surges can damage equipment, and even cause damage to property and health, for example, causing a fire.
Reference. Breakdowns of electrical appliances as a result of power surges are not covered by warranty contracts, that is, the burden of repair and replacement costs falls on the owner, which can be a serious blow to the family budget. In some cases, it is possible to sue the electricity supplier, but this is long, difficult and expensive, and does not guarantee success.It is easier to foresee the protection of your home from such troubles.
Ways to protect against power surges
Depending on the characteristics of the voltage surge and the nature of its occurrence, various protection devices are used. Let's consider the main ones:
Network filter
A simple and affordable solution for protecting low power equipment. Usually it is an extension cord or a monoblock with a plug, socket (or sockets) and a switch with an indication of power supply. Surge protectors should be distinguished from ordinary extension cords, which do not have protection, but are very similar in appearance. Protects against surges up to 400 - 500 volts, and the load current cannot exceed 5 - 15 A.
Reference. From the technical side, the surge protector is a simple system of several capacitors and inductors. At the same time, the power supplies of most modern electrical appliances already incorporate circuits that perform a similar function. That is, in practice, network filters often act as a simple extension cord with additional protection against surges in the network.
Protection relay RKN and UZM
The device interrupts the power supply if the voltage is out of range. After the voltage returns to the set limits, the supply is restored (automatically or manually, depending on the model). The device is connected after the input machine.
The main advantages of RKN and UZM:
- Response speed in a few milliseconds;
- Withstands loads from 25 to 60 A;
- Small size and easy installation;
- Sufficient ranges of maximum and minimum voltage;
- Display of indicators of electric current in real time;
The device is effective for protection against a break in the neutral wire and moderate power surges. However, relays cannot provide a stable voltage and protect against a surge caused by a lightning strike.
Undervoltage release (PMM)
The device protects against high and low voltage. Effective in the event of a neutral wire break and phase imbalance in a three-phase network, but does not protect against high-voltage impulses.
The device differs in the small sizes, simplicity of installation and reasonable price.
Note. The PMM is not equipped with an automatic switch-on function, which may cause the food in the refrigerator to spoil, the space heating to stop in winter, and similar problems.
Stabilizers
Devices are used to "smooth" the supply of electricity in networks prone to unstable operation. Effective in the event of a power drop, but may not be able to cope with high voltage.
The advantages of the device include: long service life; fast response; maintaining the voltage at a stable level. The main disadvantage of stabilizers is the high price.
Surge protection devices (SPD)
They are used to protect against fast, powerful power surges, usually caused by lightning strikes into power lines. There are two types of such devices:
- Valve and spark arresters. They are installed in high voltage networks. In the event of an impulse overvoltage in the device, an air gap breakdown occurs, the phase closes to ground, the discharge goes into the ground;
- Overvoltage limiters (OPN). Unlike arresters, they are small in size and are used in private homes. A varistor is installed inside. At a normal voltage, current does not flow through it, but in the case of a jump, an increase in current occurs, which allows the voltage to be reduced to a normal value.
Overvoltage sensor (TPN)
It is used together with RCD (residual current device) or differential machine. DPN determines the excess of the established voltage norm, after which the RCD opens the circuit.
Conclusion
The most common means of protection against power surges: automatic machines and plugs, are not effective in all cases. In particular, they cannot cope with powerful power surges, which endangers the safety of electrical engineering and the whole house as a whole. The market offers a variety of power protection devices, used depending on the nature of voltage drops and the reasons for their occurrence. It remains for consumers of electricity to choose the necessary devices and install them correctly.
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