Reliability assurance of HVDC thyristor valves by rigorous type tests

Rigorous type tests are essential to ensure the reliability of HVDC thyristor valves. A conventional six-pulse back-to-back direct test circuit is a proper representative of an actual network to test the valves. The test equivalence by this circuit has been proven by the reliable operations of valves installed worldwide. To keep pace with the fast development of power handling capability per single thyristor, an alternative test circuit, synthetic test circuit has been developed to continuously hold the stringent type test program of ABB s HVDC thyristor valves. With properly defined test parameters, both the conventional six-pulse back-to-back direct test circuit and the synthetic test circuit can produce the stresses equal to or greater than the worst-case service stresses. As a result, higher reliability is exhibited by the tested valves.