TVSS devices are classified by the maximum ___ measured on a per-phase basis.

• A. Surge current
• B. Nominal voltage
• C. Rated power
• D. Resistive load

Answer: (A)

Surge protection devices are rated by how much transient current they can safely divert on each phase. This maximum surge current rating shows the largest current the device can shunt during a surge without failing, which is what determines how much protection it provides for a three‑phase system. The per‑phase basis matters because each phase can experience surges independently, so the protection needs to be specified for each line.

Nominal voltage describes the voltage level the device is designed to operate with, not how much surge current it can handle. Rated power isn’t the standard metric used to classify TVSS performance, and resistive load isn’t related to the device’s surge-handling capability.