Often, surges in the house electrical network can cause partial damage or complete failure of various electrical appliances located in the house. The effects of overvoltage can be reduced to a minimum by properly selecting and installing voltage suppressors.
As a rule, a single-phase (220V) or three-phase (380V) voltage with a frequency of 50 Hz is supplied to a private household.
Overvoltage can occur as a result of exceeding the maximum permissible parameters in the electrical network. The nature of overvoltage can be different.
Overvoltage sources in the intra-house network can be various electrical appliances connected to this network. In most cases, overvoltages can occur when devices are turned off or on (switching overvoltages). Another common cause of overvoltage is phase imbalance due to a break in the neutral wire or a short circuit in the network.
Sometimes a short-term surge in voltage (up to tens of thousands of volts) can be caused by a spark discharge of static electricity as a result of the contact of several objects made of insulating and conductive materials. As you can see, there are a large number of all kinds of threats to the performance of in-house power equipment.
In order to safely operate electrical appliances, to ensure their trouble-free operation, it is necessary to equip the house electrical wiring with appropriate protective devices. Let’s look at the main surge protection devices most commonly used in private households.
Lightning protection. One of the most dangerous surges in the electrical network can be a direct lightning strike on an external power line. Regardless of whether the strike occurred near the house or a few kilometers before it, the overvoltage along the supply wires will in any case be transmitted to the house. When lightning hits a power line, the lightning discharge current pulse can be several thousand amperes, and a strong electromagnetic field induces a voltage in the network that is much higher than the rated voltage of the network. As a result of this, all electrical devices (computer, TV, music center, home theater, etc.) that are not equipped with protection devices will either be damaged or even destroyed. Currently, the installation of lightning protection for private houses is not mandatory, but for our own safety and to ensure the safety of the operation of electrical appliances, we still recommend installing it.
Surge arresters. An effective method of dealing with communication and atmospheric surges is the installation of special protective devices, such as surge arresters and lightning protection, as well as the implementation of electrically equalizing connections of all intra-house metal structures to each other and to the ground loop. The performance of this scope of work must be entrusted to a qualified electrician who has group 3 access to work with electrical equipment up to 1000V. Class B limiters. To protect the house electrical network, it is recommended to use class B limiters as the first degree of protection. This device is designed to directly protect the house from the effects of current arising from lightning discharges, to equalize the potential in the building, and also serves as reliable protection against various communication and atmospheric surges arising in power lines outside the house. They are recommended to be installed in houses with overhead electrical input, which are most exposed to high lightning current, or have lightning protection. Class B limiters are installed directly at the point of entry into the house, in the main switchboard (MSB). If there is not enough space in the main switchboard, then it can be placed in a separate cabinet nearby, but in any case it should be located directly behind the electric meter before entering the main switchboard. The arrester must have a connection for each of the input phases and an earth, as well as a connection between earth and neutral. At the moment of occurrence of a dangerous electrical overvoltage, the class B arrester is able to protect the main switchboard equipment, input circuits and house electrical equipment from overvoltage. Class C arresters. They serve to protect against overvoltage of electrical in-house equipment caused by various switching loads and lightning discharges, previously limited using class B arresters.
Class C limiters must be installed:
as the first degree of protection in houses with cable entry (class B limiters are not installed in such houses),
as a second degree of protection in houses with overhead electrical input and/or lightning protection. If the length of the intra-house network is less than 20 meters, it is enough to use one class C limiter to protect the entire network.
If the length of the network with branches is more than 20 meters, it is necessary to mount it to the limiter every 20 meters (in multi-storey buildings through the estimated number of floors in the switchboard). In private houses, it is necessary to mount a class C limiter in the switchboard (together where a suitable main wire is branched into a circuit), but at a distance of no more than 20 meters from the protected devices. For most intra-house networks, the use of two levels of protection is sufficient. Class D arresters These arresters are specially made to protect sensitive and expensive electrical appliances, such as alarm central points, servers, scanners, home theaters, large LCD or plasma panels. Class D limiters are installed directly in front of the protected device (in a box, in a socket) and specifically protect only this device. Please note that the installation of a class D limiter makes sense only if the first and second degrees of protection are implemented in this house, since even a small overvoltage can damage it if it was not reduced in the early stages of protection.
To protect telecommunication and antenna lines from overvoltage, special limiters are installed directly in front of the protected devices (fax, computer, TV). At the same time, electrical appliances receive reliable protection, both through the power supply network and through the data transmission line. The use of these limiters is recommended for separately located buildings with an individual television antenna on the roof or with an overhead input of a telecommunications line (cable TV, Internet, telephone).
Static surge protection can be effectively limited by grounding by grounding an ESD-accumulating appliance (washing machine, microwave oven, TV, etc.). Increased humidity in the room (over 70%) significantly reduces the manifestation of electrostatic phenomena.
Summing up, I would like to give the average cost of currently proposed limiters. Thus, the average price of a three-phase class B limiter is currently from 6.500 UAH, a single-phase one – from 1.500 UAH. Class C limiters have a price range from 1.500 to 1.800 UAH. Combined limiters are commercially available that perform protective functions of both B and C classes at once. The price for them starts from 3.000 UAH. Class D arresters have a wide range of prices. So a limiter for installation in a mounting box will cost you from 300 UAH, for installation in a switchboard at a branching point from 500 UAH, and for protecting telecommunication lines about 1,500 UAH.
Properly performed protection of intra-house networks from overvoltage will allow you to safely operate various electrical appliances, protect them from damage and failure, and also help save the family budget from unforeseen expenses associated with the cost of restoring their performance.