Recent developments in generator circuit breakers

The self-blast technique of interruption for SF/sub 6/ 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 kV. The paper shows the application of this technique to the development of SF/sub 6/ 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.

I. Introduction

Generator circuit breakers, which are located between a generator and the step-up transformer, are an economical and efficient solution for the protection of generators and transformers. They are widely used nowadays for generator ratings ranging from 100 MVA to 1300 MVA.