Alstom Mcgg22d1cb0753c – Feeder Overcurrent

Calculation method for instantaneous overcurrent protection of relay protection

IOCP settings depend on maximum short-circuit current and protection coverage, following IEC 60909 (short-circuit current calculation) and IEC 60255-151 (overcurrent protection settings). (1) Instantaneous Pickup Setting (Iinst) Iinst = Krel × I(3)k. Its defining feature is zero intentional time delay (or minimal delay), with typical operating times of 20–50 ms, complying with IEC 60255-151 (Overcurrent Protection. Relay coordination is the process of selecting settings that will assure that the relays will operate in a reliable and selective way. Instantaneous units should be set so they. Instantaneous overcurrent protection is where a protective relay initiates a breaker trip based on current exceeding a pre-programmed “pickup” value for any length of time. The protection operates with a definite time characteristic.