SETTING CALCULATIONS FOR HIGH VOLTAGE SHUNT CAPACITOR BANK PROTECTION AND VERIFICATION OF RELAY PROTECTION OPERATION USING REAL-TIME HARDWARE-IN-THE-LOOP TESTING

Capacitor banks are crucial for power factor correction and voltage stability improving the efficiency of the power system. This paper presents a methodology for setting calculations of protection devices for shunt capacitor banks using a practical example. In this example, capacitor banks with an installed capacity of 140 MVAr are connected to a high‑voltage 345 kV network and configured in a grounded double wye formation. For the high‑voltage shunt capacitor bank protection, both primary and secondary relay protection systems were utilized. As the main protection function voltage differential protection has been used, while backup functions included phase and ground overcurrent protection with both inverse and definite-time elements, overvoltage and undervoltage protection, and an overvoltage element as permissive condition for power circuit breaker of capacitor bank to close. The criteria for setting these protection functions are presented in detail, along with calculations performed to this specific case. Since the primary protection device did not have factory-implemented voltage differential protection but supported protection free-form logic settings, the logic for voltage differential protection was programmed within the device. Considering the importance of the protected capacitor bank, the operation of the protection device was tested using real-time hardware-in-the-loop (RT-HIL). The paper describes the testing procedures and the results, which confirmed the correct operation of the capacitor bank voltage differential protection developed in freely programmable logic of the device.