Residual Voltage Of Surge Protector And Its Three Parameter Selections

Residual voltage Ures of surge protective device

This is the actual voltage applied to the terminals of the protected equipment. The lower the residual voltage, the better. It should be less than the surge overvoltage rating of the protected equipment:

1220/380V three-phase system surge overvoltage rating Uw for various equipment

Nominal discharge current In of surge protector

This is used to classify SPDs. It has a discharge current of 8/20µs or 10/350µs, simulating a lightning current surge. Imax = 2-3 In.

Continuous operating current Ic of surge protection device

The current flowing in the protection mode at the maximum continuous operating voltage Uc is actually the sum of the currents flowing through each protective element and its parallel internal auxiliary circuits. Selecting the Ic value is very important to avoid unnecessary operation of overcurrent protection devices or other protective devices (such as RCDs). Under normal conditions, Ic should not cause any personal safety hazards (non-direct contact) or equipment failure (such as RCDs). Generally, for RCDs, Ic should be less than 1/3 of the rated residual voltage current value (I△n).