Analysis of OCR and GFR Coordination on the 20 kV Cubicle at Mosad Office Tower Samarinda

The distribution system is a component of the electric power system responsible for delivering electricity from the transmission network to consumers. This system generally utilizes medium voltage levels, which are more susceptible to faults compared to transmission systems. To mitigate disturbances in the distribution network, protection equipment is employed. Commonly used protection devices include the Overcurrent Relay (OCR) and the Ground Fault Relay (GFR). Coordination between the OCR and GFR is essential to ensure the protection system functions optimally, possesses adequate selectivity and sensitivity, and maintains the continuity of electricity supply. This paper discusses the coordination settings of the overcurrent and ground fault relays. Simulations were conducted using ETAP 19.0.1 software based on field data. Calculation results on the feeder indicate an OCR grading time of 0.489 seconds, whereas the field data shows 0.4 seconds. For the GFR, the grading time on the feeder is 0.297 seconds, compared to 0.4 seconds from the field data. These values indicate that the protection coordination within this system can be considered ideal.