Overvoltages on five legged core transformers on rural electric systems

Five-legged-core, grounded-wye-grounded-wye, three-phase transformers can cause overvoltage conditions on an open phase when the primary is cable fed and single-phase switched. Field and laboratory test results on the overvoltage condition are given. An equivalent circuit of the transformer is evaluated and used to simulate laboratory and field test conditions. Techniques to minimize the overvoltage condition are discussed.<
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