IEEE Std C37.011-2011 pdf download – IEEE Guide for the Application of Transient Recovery Voltage for AC Hig h-Voltage Circuit Brea kers.
3. Transient recovery voltage 3.1 General The recovery voltage is the voltage that appears across the terminals of a pole of a circuit breaker after interruption. This voltage may be considered in two successive time intervals: one during which a transient voltage exists (TRV), followed by a second during which a power-frequency voltage alone exists. During the interruption process the arc rapidly loses conductivity as the instantaneous current approaches zero. Within a few microseconds after current zero, current stops flowing in the circuit. The power system response to current interruption generates the TRV. TRV is the difference in the power system response voltages on the source side and on the load side of the circuit breaker. The nature of the TRV is dependent on the circuit being interrupted, whether primarily resistive, capacitive, or inductive (or some combination). Additionally, distributed and lumped circuit elements will produce different TRV waveshapes. In principle, the response of the load side and source side of the circuit breaker can be analyzed separately and the results subtracted point by point on a time line. The driving voltage is the instantaneous power- frequency voltage across the circuit elements at the instant of current interruption. The breaking operation is successful if the circuit breaker is able to withstand the TRV and the power- frequency recovery voltage.
3.2 Effect of circuit breaker on transient recovery voltage The circuit TRV can be modified by the arc of the circuit breaker. Therefore, the TRV measured across the terminals of two different types of circuit breakers under identical conditions can be different. Recognizing the modifying abilities of each of the various circuit breakers would be an immense task when either calculating a TRV or specifying a related value for the circuit breaker. To simplify both rating and application, the power system electrical characteristics are defined or calculated ignoring the effect of the circuit breaker. Thus, the TRV, which results when an ideal circuit breaker interrupts, is used as the reference for both rating and application. This TRV is called the inherent TRV. An ideal circuit breaker has no modifying effects on the electrical characteristics of a system and, when conducting, its terminal impedance is zero; at current zero its terminal impedance changes from zero to infinity.