In the last article, we talked about the difference between lightning arresters and lightning rods. In this article, we will talk about why lightning arresters must be used in some circuits.

As we know,the installation of lightning rods and lightning conductors can prevent lightning from directly hitting electrical equipment. However, due to various reasons, electrical equipment equipped with lightning rod may still be struck by lightning (such as circumventing, counterattack or not being equipped with a lightning rod and lightning cable due to conditions).

In addition, when lightning strikes the line or the ground near the line, overvoltage will be generated on the transmission line. They will be transmitted to the substation along the line in the form of waves, endangering the equipment with weak insulation in the substation. Therefore, in order to protect the electrical equipment, another overvoltage protection device must be installed, which is the arrester.

In addition to the lightning overvoltage, there is an internal overvoltage in the power system, and its size is related to the maximum operating phase voltage of the system. In the early development of the power industry, the rated voltage of the system was low, and the insulation level of electrical equipment was sufficient to withstand the effect of internal overvoltage. The threat posed by lightning overvoltage was much greater than the internal overvoltage in the system. The initial function of the arrester is to limit the lightning overvoltage. With the development of the power industry, the voltage levels are getting higher and higher, ultra-high voltage and ultra-high voltage systems are appearing one after another, the amplitude of the operating overvoltage is also getting higher and higher, and its duration is longer than the lightning overvoltage, which gives safe operation of electrical equipment bringing a serious threat. Therefore, you must use a lightning arrester to limit the internal overvoltage.