Working Principle And Selection Guide Of Surge Protector

To protect the protected equipment from overvoltage, the voltage protection level Up of the surge protective device must always be less than the impulse withstand voltage Uchoc of the protected equipment and greater than the maximum operating grid voltage Usmax derived from the grounding type, i.e., the requirement is UsmaxUpUchoc. When the equipment's impulse withstand voltage is unavailable, equipment selection for 220/380V three-phase distribution systems is recommended.

Maximum discharge current Imax for Class II classification tests

The peak current of the surge protector, 8/20μs current wave. For Class II classification tests, Imax > In.

Switching type surge protection device: Its operating principle is to present a high impedance when there is no transient overvoltage. However, in response to a lightning transient overvoltage, its impedance suddenly drops to a low value, allowing the lightning current to pass. Devices used in this type of device include discharge gaps, gas discharge tubes, and thyristors.