Dieter Braun - ABB High Voltage Technologies Ltd. Zurich Switzerland ۱. Muzaffer Canay Consultant Birr Switzerland
Saeed Kianfar - Asea Brown Boveri (PJSC) Tehran Iran Georg S. Kdppl KOEPPL POWER EXPERTS Wettingen Switzerland

Out-of-phase synchronizing occasionally occurs in power stations. The resulting fault current may exhibit delayed current zeros. Theses delayed current zeros have totally different causes and are quite dissimilar in comparison with the well-known delayed current zeros associated with generator terminal faults. The effect of circuitbreaker arc voltages on the course of the resulting fault current has been examined and a compatison made between generator voltage and high voltage circuit-breakers. From this comparison follows that while circuit-breakers on both side of the main transformer are necessary from a protection point of view, the generator circuit-breaker should preferably be used for synchronizing operations.