What is current sensitivity?

Current monitoring relays are sensitive to under-current conditions as this condition may lead to the contactor not picking up to start the motor and also pose dangerous for operation of the motor. Over-current condition occurs when there is an overload, short-circuit or when the current is higher than the set value, leading to excessive heat generation and fire or damage to device. Devices that can be damaged due to currents over a set value use current monitoring relays that are sensitive to this range of current values and which indicate fault when the current values exceed the set current value of the device. In case of over-current, also called as short-circuit as per National Electrical Code (NEC), there is a breakdown in insulation resulting in excess current which is a magnitude of the electrical load. Voltage gradually decreases as does the current but the initial current is of the full DC transient voltage at the time of short-circuit and the relay follows an inverse time delay curve.