The need to protect power networks from surge voltage arose almost immediately after people learned how to transfer electricity within a neighboring building. Often the cause of surge voltage is a lightning strike to a power line or the effect of lightning striking close to the cable. But there are other reasons, for example, switching processes in electric substations. Normally they should not lead to the appearance of dangerous surge voltage in the network, but in reality such surges appear due to worn-out equipment or insufficient staff qualifications.
The problem of controlling surge voltage has become especially urgent in our time, since computers and communications equipment are connected to the power supply network. Surge voltage can disable them. But even if the same computer does not break down, then its operation may fail with loss of information. In order to avoid such situations, SPDs (stand for surge protection devices) are used . The principle of the SPD operation is that when the voltage on the phase wire exceeds a certain value, this wire instantly connects to the ground wire, which allows you to divert the surge voltage to the ground.
Read more about the classification of SPDs, their scope, placement methods and other nuances in our article.