Setting Analysis of Over Current Relay and Ground Fault Relay on Transformer Protection System of High Voltage Substation System

Electrical energy is one of the basic needs of everyone at this time. Therefore, electrical energy must always be available economically and of good quality, such as voltage or frequency and reliability. To maintain the continuity of electric power in distributing electrical energy required protection system is needed. The function of this protection system is to detect and disrupt power network interruptions from other non-interrupted networks as quickly as possible with the intention that greater losses are avoided. The usual disturbances are 3 phase, 2 phase, and 1 phase short circuits. To secure the electrical power system from various disturbances, especially the transformer, the protection relay is very important. The protective relays are used for a transformer covered an overcurrent relay (OCR), ground fault relay (GFR). This paper is a calculation and analysis of the OCR/GFR based on the settings on a 60 MVA transformer at the 150 kV Cibatu Substation in West Java. The results of a comparison between the calculation and the data that is installed in the main substation is quite similar. The calculation results on the time multiplier setting (TMS) show that the OCR setting on side 20 kV plots in 0.20 of TMS while the OCR setting on 150 kV side obtains in 0.23 of TMS. Moreover, the GFR is adjusted on 20 kV side obtained 0.18 of TMS while the GFR setting on 150 kV side is 0.107 for the TMS. In general, these studies show that the settings installed on Cibatu Substation is still in good condition but it needs monitoring to face load demand changes.