Surge and surge protection

During the operation of electrical equipment, it is possible to be damaged not only by a short circuit, but also by a lightning discharge in its circuits, penetration of a higher voltage from other equipment or a significant reduction in the level of the power circuit.

According to the value of the effective voltage, the protection is divided into two types:

1. minimum;

2. maximum.

Low voltage protection

In the case of short-circuit emergencies, large energy losses occur when the applied power is spent on the development of damage. In this case, huge currents occur and the voltage level drops sharply.

The same picture, but less clearly, occurs when the circuit is overloaded, when the power of the voltage sources is clearly not enough.

This principle is used in the operation of protections that monitor the voltage in the network and open the circuit breaker when the voltage drops to the lowest possible value - the setting.

Such circuits are called low voltage protections.They can be configured to shut down or alert service personnel.

Their measuring device is similar in structure to that used in overcurrent protection. But it has its own design features.

Includes:

• instrument voltage transformer (VT)conversion of the primary voltage of the network into a proportional value of the secondary with high accuracy, limited by the permissible metrological characteristics;

• the undervoltage relay (PH) configured to operate when the level controlled by it falls to the set value;

• an electrical circuit of voltage circuits by which the secondary vector is transmitted from the voltage transformer to the voltage relay with minimum losses and errors.

Low voltage protections operate autonomously and can be configured for joint, complex use with other devices, for example overcurrent protection or power monitoring.

Surge protection

There are two types of devices that protect electrical equipment from overvoltage.

Protections operating on the principle of a lightning discharge from a lightning rod to the potential of the earth loop and extinguishing its energy due to the dissipation of heat in the surrounding atmosphere, as a certain part of voltage limiters. They do not use a relay base, but work directly in the supply circuit.

Surge relays are created according to the step-down principle with the same measuring elements, but the voltage relay itself is configured to operate at a set increase value that exceeds a certain allowable voltage level for the working circuit.

See also on this topic: Connection diagrams of voltage measuring transformers