The standard parameter for comparing surge suppression devices is expressed in which per-phase unit?

The standard parameter for comparing surge suppression devices is expressed in which per-phase unit?

• A. kW/phase
• B. VA/phase
• C. kV/phase
• D. kA/phase

Answer: (D)

Surge protection devices are evaluated by how much transient current they can safely carry on each phase. The key rating is the surge current capacity, expressed in kiloamperes per phase. This per-phase rating matters because, in a three‑phase system, each phase can experience a surge independently, and the device must handle that current on every phase without failing. Other units describe voltage or power, not the device’s ability to conduct surge current, so they don’t provide the essential measure for comparing surge capability. Therefore, the standard parameter used to compare SPD performance is kA per phase.

Surge protection devices are evaluated by how much transient current they can safely carry on each phase. The key rating is the surge current capacity, expressed in kiloamperes per phase. This per-phase rating matters because, in a three‑phase system, each phase can experience a surge independently, and the device must handle that current on every phase without failing. Other units describe voltage or power, not the device’s ability to conduct surge current, so they don’t provide the essential measure for comparing surge capability. Therefore, the standard parameter used to compare SPD performance is kA per phase.