Abstract:
A new method for optimizing overcurrent relay
(OCR) settings and coordination in interconnected power
systems was developed. The method considers factors such as
feeder impedance equivalences, phase-to-phase fault currents,
current settings of 110kV incoming and 15kV outgoing feeders,
and operating times for relay characteristics (standard, very,
and extremely inverse of overcurrent relay). The maximum
fault current of the interconnected power grids is also
considered. Power system parameters like X/R ratio, current
transformer ratio, transmission line length, resistances,
inductances, full load current, line capacity, CT ratio for
outgoing feeders, grid frequency, and real power are also
considered. To ensure safety and rapid operation of
overcurrent relays, settings such as pickup value, time setting
multiplier (TMS), and OCR characteristics are carefully
considered. The results show that the OCRs coordination
interval time to fastest clear faults range from 0.0927 sec-0.062
sec to 0.0764 sec-0.0661 sec for extremely, very, and standard
inverse relays, respectively.