20kV Busbar Protection Design Development to Overcome Various Disturbances Caused by Transformer Loading Configurations

In 2019, PLN UIT JBB (Western Java Transmission Main Unit) implemented 20kV busbar protection by coordinating incoming and non-cascade feeder protection. However, when the fault occurs in parallel feeders or when the Feeder is transferred to another busbar transformer with coupler facilities. The 20kV busbar protection design does not work correctly in isolating the faults due to fault coordination logic between busbar protection feeders and incoming. Therefore, the authors propose a new concept by changing the non-cascade protection scheme setting, which initially used a moment fault current sensor of 230% of the Transformer's nominal current (4000A) to a current sensor from a Time Multiple Setting with a current magnitude of 120% of the nominal current Feeder (320A). The authors also added a 20kV coupler as the 20kV busbar protection part. This scheme has been tested in a laboratory using a multi-tester protection relay with the results. The new design of the 20kV busbar protection can localize the disturbance correctly, being more selective and reliable to accommodate five different types of disturbances.