Theory of Yd transformer faults

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For the Yd11 transformer, in the case of a two-phase short circuit on the d side: in terms of current, the current in the phase that is lagging with respect to the faulty phase is the highest; this value is 2/√3 times the current in the faulty phase. The currents in the other two phases are in the opposite direction and equal to half of that value. For example, if phases a and b are short-circuited, the current in phase B is the highest. In terms of voltage, the voltage in the phase that is lagging with respect to the faulty phase is the lowest, being twice the internal voltage drop of the transformer. The voltages in the other two phases are higher, with the line voltages being the highest. For the Yd11 transformer, in the case of a single-phase ground fault on the Y side: In terms of current, the current in the phase that is lagging behind the faulty phase is 0; the currents in the other two phases are equal but in opposite directions, and they amount to 1/√3 times the current in the faulty phase. In terms of voltage, the voltage in the phase that is lagging behind the faulty phase is the highest; the voltages in the other two phases are equal, while the inter-phase voltage is relatively high.