Electric power distribution system is a system that is useful for distributing electric
power from substations to consumers, which are inseparable from problems, including
short circuit current interference. To localize the interference, a protection system is
needed that meets the requirements of sensitivity, reliability, selectivity and speed.
MJN 08 feeders have a length of 32.950 km with over current relay (OCR) and ground
fauly relay (GFR) that serve to give orders to Reclosers or PMT. In the study of short
circuit current and protection coordination in MJN 08 feeders manual calculations and
simulations using ETAP were performed. The results of calculations and simulations
of short circuit currents are known that the farther the point of disturbance that occurs,
the short circuit current will be smaller. The results of the protective coordination
manual calculation of the 3 phase short circuit current relay work time are 0.301
seconds - 0.534 seconds and in the simulation with ETAP 0.303 seconds - 0.532
seconds, while the manual calculation of 2 phase short circuit current is 0.331 seconds
- 0.755 seconds, and ETAP simulation is 0.319 seconds - 0.582 seconds. OCR working
time is approaching the SPLN standard, which is 0.35 seconds - 0.4 seconds, but has a
difference of 0.1 seconds slower. The results of manual 1-to-ground short circuit
calculation are 0.765 seconds - 1.496 seconds while ETAP simulation is 0.706 seconds
- 1.243 seconds. From the results of calculations and simulations the value of GFR
protection work time is not in accordance with the SPLN