Isc Function: The short-circuit current is given by Isc = S / (V * PF) Isc_Relay Function: The secondary short-circuit current is given by Isc_Relay = Isc / CT Pickup Function: The relay pickup current is given by Pickup = Relay * VTIsc Function: The short-circuit current is given by Isc = S / (V * PF) Isc_Relay Function: The secondary short-circuit current is given by Isc_Relay = Isc / CT Pickup Function: The relay pickup current is given by Pickup = Relay * VTSelective short-circuit protection can be achieved in different ways, such as: Time-graded protection Time- and current-graded protection A straightforward way of obtaining selective protection is to use time grading. The principle is to grade the operating times of the relays in such a way that. This calculator provides the calculation of short-circuit current and relay pickup current for protective relaying applications. Calculation Example: Protective relaying is a system of devices that detect and respond to abnormal conditions in an electrical power system. Understanding each setting facilitates proper relay coordination. Plug Setting Multiplier (PSM):. LAY S TTIN LAY SETTIN of CT groups fCalculate pickup values, timing curves, coordination time intervals (CTI), and test injection currents for overcurrent (50/51), differential (87), distance (21), and directional (67) protective relays.
