Electrostatic Voltage Distribution and Transfer in 3-Winding Transformers [includes discussion]

When a steep-front surge impinges upon a transformer winding, an electrostatic voltage distribution is immediately established along all the transformer windings. This paper discusses this electrostatic distribution in the impulsed and in the two nonimpulsed windings of 3-winding transformers, and expressions of the electrostatic voltages are derived analytically for various terminal conditions of the nonimpulsed windings. The line terminals of these windings may be isolated, grounded directly, or grounded through a capacitor. Computed voltages are in good agreement with the initial voltages measured on a 667-kva single-phase transformer and on its electromagnetic model, and also with the voltages measured on a capacitance board representing only the electrostatic field of the transformer.