Which of the following is not one of the standard five common overcurrent protection trip types?

• A. Instantaneous trip (I)
• B. Long-time trip (L)
• C. Short-time trip (S)
• D. Normal-time trip

Answer: (D)

Overcurrent protection uses different timing schemes to decide how quickly a device should trip after the current exceeds the pickup. The common categories describe how the protection responds: instantaneous trips react right away when the threshold is reached to stop a severe fault; long-time trips add a longer delay and often use an inverse-time relationship so prolonged overloads are cleared without tripping for short glitches; short-time trips introduce a brief delay to allow short transients to pass while still providing protection. A designation like normal-time trip isn’t a recognized category in these standard schemes—there isn’t a defined “normal-time” timing curve used in protection practices. That’s why it isn’t considered one of the standard trip types, while instantaneous, short-time, and long-time reflect real, defined timing behaviors used in protection settings.