If a fault current is in the current-limiting range of a current-limiting OCPD, the fault current's magnitude and time duration are both increased, which increases the energy released by an arcing fault.

• A. True
• B. False
• C. Not enough information
• D. It reduces energy

Answer: (B)

Current-limiting OCPDs are designed to keep energy released by an arcing fault as low as possible by reducing both how large the fault current can get and how long the arc lasts. When a fault current falls within their current-limiting range, the device acts quickly to clamp the current and interrupt the arc, so the energy let-through is decreased (energy is roughly proportional to I^2 times the time the arc remains). Therefore, saying that both the current magnitude and the duration increase is not correct—the energy is actually reduced.