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To calculate the overvoltages in transformer windings under very fast transient overvoltages (VFTOs) generated by switching operations in gas-insulated substation (GIS), a single-input and multiple-output circuit model, which is based on a multiconductor transmission line (MTL) model, is presented in this paper. The procedure to determine the transfer function is deduced. Vector fitting and recursive convolution are used to calculate the time domain response. The resonant frequencies and the location of the resonance are determined by an analysis of the amplitude-frequency response characteristics. For validation, the calculated results are compared with the measurements on a transformer winding model, and the results are found to be satisfactory. Index Terms--Resonance, transformer windings, vector fitting, very fast transient overvoltage (VFTO).

Calculation of magnetic vector potential A is fundamental in the partial element equivalent circuit method, which directly affects the value of inductive part, called partial inductance. All of the existing methods for partial inductance are based on Lorenz gauge. This paper presents an analytical method for calculation of partial inductance with Coulomb gauge in quasi-static field. The difference lays on the calculation of A, which has an obvious impact in open loop problems. Some analytical results of conductor segments are derived for comparison of two different gauges, and show the difference between the proposed method and existing methods. Numerical experiments of the self- and mutual-partial inductances of conductor segments in open loop problems are also given. The results illustrate that the proposed method is consistent with the energy method, whereas the existing method gives different values, especially for short conductor segments whose difference might reach 50%. The proposed method may also be applied to closed loop problems and give same results with existing method. [ABSTRACT FROM AUTHOR]