A Method for Controlled Fault Interruption for Use with HV SF6 Circuit Breakers

A method has been developed for synchronizing the trip commands to a HV circuit breaker in order to achieve a preselected optimum arcing time, even under transient asymmetrical fault current conditions. The algorithm estimates parameters of the fault current by applying least means squares regression to a generic model and sampled values of the current in each phase. An analysis of variance is made between the sampled and modeled currents to provide additional control and as a basis for discrimination between grounded and ungrounded fault cases. In addition, high power experiments have been conducted to investigate the stability of minimum arcing times of HV SF6 circuit breakers over a large succession of interruptions. The data from these experiments indicates good stability in the minimum arcing time behavior, thus providing important information for the viability of synchronizing circuit breakers in order to avoid unnecessarily long arcing times.