Ferroresonant Overvoltage Control Based on TNA Tests on Three-Phase Wye-Delta Transformer Banks

This paper shows possible ferroresonant overvoltages on wye-delta transformer banks during single-phase switching as a function of transformer size and lateral length. Application guide is based on industry standard voltage criteria. Secondary loading and neutral resistor requirements are given. A neutral resistor presents an attractive solution in many cases. Simple to use equations are given to allow application of test data.