DEVELOPMENT AND FABRICATION OF CIRCUIT BREAKER SYNTHETIC TESTING UNIT

Abstract

Development in electrical power transmission systems require the use of circuit breakers with increasing breaking capacity. At this moment, circuit breakers are to be installed on 245kV to 800 kV power systems, with short circuit ratings upto 63 kA. To test this equipment, direct testing, using the power system or short circuit alternators, is no longer feasible. This means that synthetic tests, now no longer considered as an alternative to direct tests but as equivalent to them, are vitally important. The testing of HV circuit breakers oflarge capacity requires very large capacity of the testing station which is uneconomical. It is also not practical to increase the short-circuit capacity of the testing station. Therefore, indirect method of testing are used for testing of large circuit breakers. The short-. circuit power available in testing stations (which is of the order of 4000 MVA in laboratory type testing station) is not sufficient to test a complete breaker (which is of rated breaking capacity of the order of 10,000 MVA at 245 kV). Even single pole of a EHV CB cannot be tested by direct means. This Dissertation report presents transient recovery voltage (TRV) rating concepts, TRV circuits, computer aided design of synthetic testing test circuit and development and fabrication of CB synthetic testing test circuit (Proto type). Developed CB synthetic testing test circuit is parallel current injection test circuit (Weil-Dobke type) because parallel current injection method is widely used for testing circuit breakers as it is capable of providing RRRV and recovery voltage as required by various standards. Some experimental results of developed circuit and calculated results are also given.