The testing of generator circuit-breakers

Generator circuit-breakers face much higher current and voltage stress than distribution switchgear. This has led to a special standard (ANSI C37.013). Strictly in accordance with this standard's requirements, test circuits and parameters for a 100 kA and 120 kA (25.3 kV) SF6 generator circuit-breaker have been defined. The circuit-breaker is equipped with capacitors at both sides of the extinction chambers. The effect of these is to reduce the TRV severity and this is quantified for the relevant switching duties. Adequate test-circuits are described. Also, the optional verification of interruption of generator-fed faults with very large DC components has been demonstrated. Herein, delayed current zero can extend arcing time. The importance of arc voltage in reducing the longer arcing time is illustrated in a calculated example