A system of surge protection devices (SPD) is designed to protect electrical and electronic equipment from lightning strikes. The connection diagram in a private house is carried out for the purpose of safety or uninterrupted operation. In the first case, consumers are completely disconnected, and in the second, their safe operation is ensured.
Content
- Types of surge voltages
- Primary funds
- SPD classification
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Connection diagrams
- External system
- Installing protection on a branch
Types of surge voltages
Lightning voltage is calculated in tens, and sometimes hundreds of thousands of volts. Therefore, in a short period, it causes considerable harm, disabling household appliances. In refrigerators, the compressor motor breaks down, the primary circuit of the converter burns out in the power supplies, etc.
At this moment, an overvoltage in the electrical circuit is of great danger, since there is a high probability of a fire. Causes of power surges:
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Lightning is characterized by a rapid impulse that breaks through the network, since its power is several times higher than that of conductors. It enters the electrical line, and then the equipment inside the house, and is expressed by the ratio of the voltage amplitude of 10 kV to the duration of its flow - 350 μs.
- Overvoltage is caused by faults in electrical circuits caused by switching processes. This could be the result of an accident at a power plant or when switching from one generator to another. At this moment, a powerful impulse can arise in the secondary network, which causes harm commensurate with lightning.
Overvoltage is characterized as an emergency state of the system during the generation of electrical energy. Therefore, in order to protect electrical equipment from the occurrence of negative impulses, an SPD is installed for a private house.
Primary funds
The installation of surge protective devices is considered only part of the procedure for protecting against the outbreak of fire or electrical equipment failure. The primary means of protection against the effects of lightning should be provided in advance. These include:
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A metal bus should be laid around a private house and closed, which will serve as a grounding around the entire perimeter. - Lightning rods are connected to the plates along the edges of the house.
- The main lightning rod is mounted on the roof. If the design is too large, then the lightning rods are divided into several elements.
- This is especially true for private houses with a metal roof, if an electrical network runs next to it.
In addition to the effects of lightning impulses, other possibilities of interference penetration into the house should be taken into account. A sharp increase in voltage can occur during the connection of high-voltage devices at the substation.
The impulse penetrates through the television cable and enters the television, which will most likely fail. The same situation can arise with an Internet cable, overvoltage through which makes a personal computer unusable. In difficult situations, a fire source may arise.
To prevent these negative phenomena, all lines and equipment should be connected to the ground loop, and completely de-energized during lightning. It is almost impossible to provide it manually, therefore there is an automatic protection of low-voltage networks.
SPD classification
There are 3 classes of varieties of surge protection devices. Class 1 has the ability to pass through itself and withstand all the energy from lightning. Such devices are installed in rural areas with overhead electric lines. In addition, it is recommended to install them in houses with lightning rods or buildings located next to tall objects. Such devices are not installed in apartments or administrative premises.
Class 2 device not applicable without the first device, as it is not able to withstand the power of a lightning strike. Its effectiveness is manifested only when used together.
Class 3 device it is not used without the two previous devices and it is installed directly in front of the consumer. This type includes a surge protector or protection in the power supplies of some household units.
Connection diagrams
There are several SPD connection schemes for the protection of low-voltage networks. The complex application of devices is considered an ideal option, since a lightning strike is absolutely unpredictable.
External system
An external protection element is assumed on the basis that a maximum current can flow through its components. The protective device is installed with the ability to withstand 100 kA. To prevent a negative impulse from causing much trouble, it should be diverted along the path of least resistance.
For this, a complex SPD is installed in the electrical panel, which includes three degrees of protection. This device has a high power and response speed, protecting equipment with a total power of up to 20 kW.
Directly the scheme of its connection depends on the type of the ground loop.
If this is grounding divided into two sections, then two separate buses are mounted in the shield: zero, grounding. A jumper is installed between them, which is considered additional protection.
Installing protection on a branch
It is possible to install the SPD not in the switchboard, but directly on the branch of the electrical network. For example, where an overhead line diverges into two neighboring houses, and the ground loop does not have lightning rods.
Sometimes the device is installed in front of the entrance to the house and the use of an SPD with a 3 class of protection is irrational. Devices with class 1 and 2 are mounted. If the distance from the post to the house exceeds 60 m, then an additional device with 2 protection class is installed in the electrical panel.
The method of installing protection is different if the house is connected to an underground cable. An emergency situation arises from other external sources, so the duration of the impulse noise will be much shorter. For protection, it will be enough to install a class 2 SPD in the switchboard.
In addition to electrical lines, overvoltage can occur in television networks. High voltage interference is often generated at antenna receivers in homes where there are no lightning rods. The emergence of a short-term high voltage in the antenna cable leads to the failure of the TV selector.
The protection device is an antenna adapter with a grounding device. There are two types of devices: for analogue, satellite or digital television. You can distinguish them by the corresponding inscriptions on the body: Radio / TV, SAT.
The Internet network cable also has a protective device that is installed when the wire is inserted into the building.
