Which protective function requires the most energy to trip a circuit breaker?

The long time function of a circuit breaker is designed to provide protection against overload conditions that could lead to overheating and damage to electrical equipment. It operates over a longer time frame, allowing for calculated delays in response to current levels that exceed the rated capacity of the circuit. When a long time function is triggered, it requires a significant amount of energy to sense the sustained overload conditions and to ultimately trip the breaker.

This protective mechanism is crucial for ensuring that equipment is not subjected to prolonged excessive current, which could cause failures. The trip mechanism in this case relies on thermal effects, and the energy required to heat the bimetallic strip or other sensing material to the point where it will trip the circuit breaker is considerable.

Other functions, such as ground fault protection and instantaneous protection, typically respond much faster and are designed for different scenarios. Ground fault protection focuses on detecting abnormal current flow caused by ground faults and will trip very quickly, whereas instantaneous protection is designed to react to short-circuit conditions almost immediately, demanding less overall energy for operation compared to the prolonged monitoring required for overload conditions under the long time function. Current limiting, on the other hand, operates to prevent excessive currents in the first place, thus it does not take energy in the same sense