The clamping voltage is a dynamic performance parameter, specifically referring to the peak voltage across the terminals of a surge protective device (SPD) when its core nonlinear element (such as a metal oxide varistor (MOV) or avalanche diode (TVS)) conducts and discharges a surge current of a specific waveform and amplitude. It is essentially the highest voltage established by the SPD during the dynamic suppression of overvoltage, and applied across the protected equipment.

In the protection mechanism of an SPD (Surge Protective Device), the clamping voltage plays a core role as a "voltage threshold ceiling." Its working process can be described as follows: when the transient overvoltage peak appearing on the line exceeds the activation threshold of the SPD's core component, the impedance of this component instantly changes from a high-impedance state (almost an open circuit) to a low-impedance state (almost a short circuit). At this instant, a huge surge current is discharged. Due to the inherent dynamic resistance of the component, a voltage drop occurs when the current flows through it; this voltage drop is the clamping voltage. The design goal of a high-quality SPD is to suppress the clamping voltage to the lowest possible level while being able to withstand the expected surge current.

The relationship and differences between clamping voltage and voltage protection level:

Closely related: In standards such as GB/T 18802.11, the voltage protection level of an SPD is a declared, fixed rated parameter. It is determined by rounding up the clamping voltage value measured after testing the SPD under specified test conditions (such as a specific nominal discharge current In and waveform). Therefore, the clamping voltage is the measured basis and physical essence of the voltage protection level, while the voltage protection level is the commercialized nominal value of the clamping voltage within the framework of the standard.