Closed-loop testing with the real-time digital power system simulator

Most protection and control equipment is usually tested in the open-loop mode. However, closed-loop testing is often the only cost-effective approach. This paper highlights the areas where closed-loop testing of protective relays and control equipment is preferable. Test setups with a real-time digital simulator for closed-loop testing of protective relays, power system stabilizers, and controllers for controlled closing of individual poles of a shunt capacitor breaker are described.