Medium voltage distribution network is a network of 20 kV primary distribution substations supplied from power plants or diesel using medium voltage cable line (SKTM) or medium voltage air line (SUTM). Short circuit often occurs at 20 kV network, interphase (3 phase or 2 phase), short circuit or phase to ground. If the protection is less good coordination, it can cause widespread blackout. So protective equipment used is over current relay (OCR) and ground fault relay (GFR) which will work to instruct the PMT to open so disturbed SKTM be separated from network. From the discussion known that 1 phase fault current to ground influenced by fault location and setting of ground fault relay is calculated in accordance with the conditions that have been set in the field.
Key Words : Protection, Fault Current, Ground Fault Rela
