The surge protector is an important device for preventing overvoltage impact of electrical equipment in buildings. Under the protection of SPD, even if the lightning current of up to tens of kiloamps invades the internal circuit, the surge protector can quickly discharge to the underground grounding grid, to protect the stable and safe operation of our electrical equipment. However, in recent years, the fire problem of surge protector devices has occurred from time to time. Whether the surge protector is safe or not and why the surge protector burns out has become a concern for users. Today, we will give you a popular science on why the surge protector burns out.
Lightning current, usually has a high current, fast speed characteristics, usually in dozens or hundreds of microseconds will pass tens of kiloamperes of high current, if not discharged, will cause fatal consequences on the use of electrical equipment and human life. Surge protector using pressure-sensitive resistors or discharge gaps, in normal operation is equivalent to a great resistance and does not affect the normal work of other electrical equipment, in the lightning current intrusion line quickly conduct, the lightning current short-circuit to the branch and discharge to grounding devices. The SPD state caused by direct strong lightning current is usually blown up, and there is simply no time for the SPD to burn. So why does the surge protector device burn out?
The surge protector device has been used on the line for a long time, and it will gradually deteriorate. At this time, when the large equipment on the line starts to operate, an operating overvoltage will be generated. This operating overvoltage may cause the varistor to generate short-circuit current. According to Electric heat generation formula, once the heat reaches a certain level, the surge protector will generate a lot of heat and cause a fire to be burned out. Therefore, the surge protector is burned out, usually caused by short-circuit current.
Because of this, it is clearly stipulated in GB 51348-2019 that the front end of the surge protector must be equipped with a special SPD backup protector. When a short-circuit current occurs in the line, the surge backup protector is quickly disconnected, so that the surge protector is protected, this way the surge protector won’t burn out.