Differential Relay Protection Testing on Strating Transformer of PLTU Units 3 and 4 at PT PLN Nusantara Power UP Gresik

Abstract

The reliability of the transformer protection system has an important role in maintaining the continuity of power plant operations. One of the main components in the protection system is a differential protection relay that functions to detect internal interference in the transformer. This study aims to evaluate the performance of differential protection relays on Starting Transformers at PLTU Unit 3 and Unit 4 of PT PLN Nusantara Power UP Gresik. This research is focused on the analysis of the accuracy and response of relay operations based on the results of the tests conducted. The testing process was carried out using the OMICRON CMC 356 test kit with the help of the Test Universe lubricant through the current injection method to simulate various system operating conditions. Some of the test parameters carried out include MV Side, LV Side, Balance Condition, Minimum Pickup, and Slope relay characteristics testing. The test results are then compared with the set value of the relay that has been set to find out the level of deviation between the value of the test result and the setting parameter used. The results showed that the highest differential current error value obtained from the test was 0.54% which was still far below the permissible tolerance based on the IEC 60255 standard, which was ±5% to ±10%. In addition, the allowable relay operating time is in the range of 34.3 ms to 39.7 ms for various test conditions that are still within the permissible operating time range of 20 ms to 50 ms. Testing under balanced conditions also shows that the relay is in a No Trip condition so that it shows the stability of the protection system under normal conditions.