The paper establishes and assesses the performance of a numerical relay SEL387 model concerning the protection of the 115/24kV transformer at Lang Co Substation by Matlab/Simulink. The paper also calculates the setting value of two actual slope characteristics (O87P = , U87P = 10, SLP1 = 25%, SLP2 = 50% and IRS1 = 3). | 8 Le Kim Hung, Vu Phan Huan PERFORMANCE ANALYSIS AND ASSESSMENT OF A TRANSFORMER DIFFERENT PROTECTION RELAY SEL387 AT 110KV LANG CO SUBSTATION 1 Le Kim Hung1, Vu Phan Huan2 University of Science and Technology – The University of Danang; lekimhung@ 2 Center Electrical Testing Company Limited; vuphanhuan@ Abstract - Based on the influences of current transformer connection type, CT errors, magnetizing inrush current, errors because of tap changing and fault conditions on differential protection function, the paper establishes and assesses the performance of a numerical relay SEL387 model concerning the protection of the 115/24kV transformer at Lang Co Substation by Matlab/Simulink. The paper also calculates the setting value of two actual slope characteristics (O87P = , U87P = 10, SLP1 = 25%, SLP2 = 50% and IRS1 = 3). The results can be applied to increase the accurate and reliable performance of the differential transformer protection relay against internal faults. Simulation has simplified the process of selecting relay and protection system. This can improve the quality of the protection system design early, thereby reducing the number of errors found later in the operation. incorrect tap on the CT, Crossed phases, Incorrect CT polarity in design or construction [2]. In addition, there is a general lack of understanding the ground differential protection principle. In most cases, inadequate or no verification test is performed to check the correctness of the secondary current circuit. So, these errors depend on skill of testers. If the hardware has no issues, then it is very likely to be a setting problem. Unlike hardware issues, setting issues cannot be assessed by the naked eyes, so the universal relay test set and commissioning tool are required. It performs to check wiring and setting of relays, by using primary/secondary injection of currents from the test set. Key words - Different protection relay; transformer; two .
