Abstract: A two channel universal device for advanced protection from a short circuit current which evaluates a rate-of-change of current in a supply feeder and compares the current in the supply feeder and the current in load phases generating a differential signal in such a way that in normal conditions, when the load is running or starting, the differential signal is virtually zero. The differential signal and the rate-of-change of current in the supply feeder are compared with the settings of the protective device. If both the value of the rate-of-change of current and the value of the differential signal simultaneously exceed their settings, after an adjustable time delay, the device produces a signal to open the circuit. The existence of two conditions necessary to initiate the trip signal to cause the circuit to open ensures the reliable operation of this device and provides a feasible fast protection scheme.

Abstract: A two channel universal device for advanced protection from a short circuit current which evaluates a rate-of-change of current in a supply feeder and compares the current in the supply feeder and the current in load phases generating a differential signal in such a way that in normal conditions, when the load is running or starting, the differential signal is virtually zero. The differential signal and the rate-of-change of current in the supply feeder are compared with the settings of the protective device. If both the value of the rate-of-change of current and the value of the differential signal simultaneously exceed their settings, after an adjustable time delay, the device produces a signal to open the circuit. The existence of two conditions necessary to initiate the trip signal to cause the circuit to open ensures the reliable operation of this device and provides a feasible fast protection scheme.