Leakage Current Of Surge Protector And Its Three Parameter Selections

Protection Level Up

This value should be greater than the maximum limiting voltage measured at the SPD terminals and consistent with the device's withstand voltage (Uw) (1.2U p ≤ Uw). It can be selected from a range of reference values ​​(e.g., 0.108, 0.109, ..., 1, 1.2, 1.5, 1.8, 2, ..., 8, 10 kV, etc.). Currently, the best U p values ​​in the national standard are 800V and 900V.

Leakage Current

Parallel type surge protective device requires a leakage current ≤ 30 uA (Ministry of Public Security requires ≤ 20 uA), while series type surge protector requires a leakage current ≤ 0.1 mA.

Start-up Voltage Uas

In the past, the start-up voltage was considered to be the nominal varistor voltage. In reality, the current flowing through surge protection device can be much greater than the test current of 1 mA. In this case, the impact of the increased residual voltage on device protection must be considered. The time from the varistor voltage to the start-up voltage (i.e., the SPD's response time) is relatively long, approximately 100 ns. Higher start-up voltages increase the residual voltage, while lower ones increase the risk of varistor aging. Its value should not be greater than the insulation level of the protected equipment.