Impulse voltage distribution on disk winding: calculation of disk series capacitance using analytical method

Nonlinear voltage distribution along the transformer winding during a lightning overvoltage can cause severe electric stress specially to the area of the winding close to the high voltage terminals. For high voltage transformers different methods such as interleaved winding, electrostatic shield wires, and wound-in shield wires are implemented on the first few disks to improve such nonlinear voltage distribution. Through application of those methods, the series capacitance of the first few disks is increased which results in reduction of electric stress on the highest stress region close to the high voltage terminal. In this paper disk series capacitances are calculated using the energy summation method and a simplified analytical formula is derived for different configuration of disk winding construction.