Voltage Acceleration - A Basic Measure of Severity of Oscillatory Transient Recovery Voltage

Difficulty of ac circuit interruption is influenced by the time-function of the rise of transient recovery voltage (TRV) across the interrupting device following interruption. It has been common practice to express the severity (steepness) of this time-function in terms of rate of rise of the voltage. However, this approach is not definitive when applied to the initial portion of the displaced-cosine transients that are associated with lumped-element circuits ( e.g., transformer- and reactor-limited faults, series and shunt reactors, and inductive load circuits). The correct measure of initial TRV severity is shown to be acceleration, rather than rate of rise, of voltage. Expressions for acceleration of both single- and multiple- frequency transients are presented, as well as methods for determination of acceleration. Use of the voltage-acceleration concept in testing and applying interrupting devices is illustrated.