Power circuit breaker transient recovery voltages

This paper describes the effects of the system zero-sequence network impedances and bus capacitance on circuit breaker transient recovery voltage requirements for EHV systems. Three basic types of faults are considered: three-phase-to-ground terminal faults, three-phase ungrounded terminal faults, and short line faults. Comparisons are presented between conventional methods of calculation used in the ANSI and IEC Standards and a more exact method which considers a simulation of the zero-sequence impedance of the system, including frequency dependence of the line surge impedances. The sensitivity of transient recovery voltages to bus capacitance is also shown for both source and line-side capacitances. The effect of bundled subconductors clashing at high fault levels is also shown and an approximate method of predicting the clashed configuration is presented. Comments on circuit breaker testing are included.