On the Response of Interleaved Transformer Windings to Surge Voltages

The high series capacitance theory for the response of interleaved transformer windings to surge voltages is criticized from the point of view that an increased series capacitance as a result of interleaving is incompatible with the concept of a pure capacitive initial voltage distribution. A new theory is proposed according to which the distributed earth capacitances are charged up during an initial period by heavy currents flowing into the winding through surge impedances formed by the coils as a result of interleaving. Formulas are derived for the initial voltage distribution and for the maximum axial voltage gradient.