Analisis Setting Arus Relai Differensial Pada Trafo II 30 MVA PT. PLN (Persero) Gardu Induk Sutami

The protection system is a very important part in an electric power installation. The purpose of the protection system is to secure equipment from abnormal conditions as early as possible so that the disturbance does not have time to cause greater damage to the equipment. The differential relay is the main safety relay on the transformer which functions to secure the transformer when an internal fault occurs in the transformer with the working principle of this relay comparing the secondary current value on the 150 kV primary voltage side with the 20 kV side secondary voltage. This study aims to determine the calculation of the appropriate differential relay current settings. The methodology in this study is to analyze the calculation, namely the calculation of the nominal current of the transformer to determine the CT ratio in the transformer, calculating the mismatch error and calculating the differential current, calculating the resistance current, calculating the slope of the differential relay, calculating the differential relay setting current, and calculating the disturbance in the transformer. From the research conducted, the results of the mathematical calculation of the value of the differential relay setting current for Transformer II 30 MVA Sutami Substation are 0.297 A. While the value of the installed setting is 0.3 A. From these results there is a very small difference so that this calculation is in accordance with the setting value. the current in the installed differential relay and the differential relay can work optimall