A novel overcurrent test equipment for high voltage thyristor valves

The working principles as well as advantages and defects of several high voltage thyristor valve overcurrent test circuits in ABB Swiss, ABB Sweden, Toshiba, and Siemens are analyzed and compared. According to CIGRE's guidelines on intensity of both current and voltage of high voltage valve in series and the requirement of IEC's test specification on valves of both SVC and HVDC, a novel main circuit scheme for overcurrent test is proposed, in which the heating current is supplied by large current source, the overcurrent and corresponding locking voltage are supplied by resonant circuit, the special test requirements of HVDC valves is auxiliary implemented by high voltage circuit. The adjustment of the proposed test circuit is more flexible, more test modes can be offered and the test ability is also evidently improved. The voltage of the proposed test circuit is raised to 18kV, the overcurrent peak to 47kA, and the expanded frequency range is from 50Hz to 350kHz.