Which statement describes definite-time overcurrent protection as opposed to inverse-time protection?

Which statement describes definite-time overcurrent protection as opposed to inverse-time protection?

• A. Definite-time trips after a fixed interval once pickup is exceeded.
• B. Inverse-time trips after a delay that shortens as current grows.
• C. Both types operate identically with current magnitude.
• D. Neither type trips based on current.

Answer: (B)

Overcurrent protection types differ in how they time the trip after the current exceeds the pickup. Definite-time protection uses a fixed, preset time delay once the current goes above the pickup setting. It will trip after that exact interval regardless of how much the current exceeds the threshold, giving a predictable and coordinated response. Inverse-time protection, on the other hand, adjusts the delay based on how large the fault current is—the bigger the current, the shorter the delay. This means larger faults clear faster, while smaller faults wait longer. So the description that fits definite-time is: it trips after a fixed interval once pickup is exceeded. The description that fits inverse-time is that the delay shortens as current grows.

Overcurrent protection types differ in how they time the trip after the current exceeds the pickup. Definite-time protection uses a fixed, preset time delay once the current goes above the pickup setting. It will trip after that exact interval regardless of how much the current exceeds the threshold, giving a predictable and coordinated response.

Inverse-time protection, on the other hand, adjusts the delay based on how large the fault current is—the bigger the current, the shorter the delay. This means larger faults clear faster, while smaller faults wait longer.

So the description that fits definite-time is: it trips after a fixed interval once pickup is exceeded. The description that fits inverse-time is that the delay shortens as current grows.