Recent developments in generator circuit breakers.

The self-blast technique of interruption for SF6 High-Voltage circuit breakers has been developed and improved during the last fifteen years. This technique has proved to be very effective and has been widely applied to High-Voltage circuit breakers up to 800 W. The paper shows the application of this technique to the development of SF6 Generator circuit breakers with low energy spring-operated mechanisms. A particular characteristic of Generator circuit breakers is their necessary capability to interrupt short-circuit currents with delayed current zeros. As shown in this paper, this performance, required by ANSI/IEEE Standard C37.013, can be demonstrated by breaking tests and calculations. The IEEE Switchgear Committee is currently revising the standard for Generator circuit breakers in order to extend the scope to applications of less than 100 MVA rated power. The paper presents calculations that have been made to calculate TRVs (Transient Recovery Voltages) for system fed faults in the case of small Generator circuit breakers connected to the step-up transformer by cables.