How Do We Correctly Choose The Uc Value Of The Surge Protector - Professional Guidance

In SPD surge protectors, there are various nominal voltage values, such as: abbreviations Un, Uc, and Uo, etc. What do they mean? What is the relationship between them? Let's take a look!

According to the national standard GB/T 18802.12-2006 standard definition:

1. System nominal voltage: the voltage indicated by the system or equipment, some working characteristics are related to this voltage (such as 230/400V).

Note 1: Under the nominal conditions of the system, the voltage at the power supply end may be different from the nominal voltage, which is determined by the deviation of the power supply system. This part allows a deviation of ±10%.

Note 2: The relative ground (L-PE) system nominal voltage is called Un (rated operating voltage).

Note 3: The system nominal relative neutral line (L-N) voltage is called Uo (the standard phase voltage value is 220V).

2. Ucs: The maximum continuous operating voltage of the power supply system.

3. Uc (maximum continuous operating voltage): the maximum AC voltage RMS or DC voltage that can be continuously applied to the protection mode of the surge protective device. (Under normal conditions, the selection of Uc should minimize the change in the characteristics of the surge protection device (aging, thermal collapse, etc.) under normal conditions.)