Analysis of lightning surge overvoltages at substation using steady-state solution

The present paper proposes a method for analyzing lightning surge overvoltages at a substation by means of steady-state solutions. The lightning current is assumed to be periodic and representable by a Fourier series. The frequency responses of the line and substation impedances as seen from the substation entrance and the response of the steadystate solution for the open-end line voltage with the substation removed are then easily obtained. The steady-state voltage at the substation entrance is evaluated from the above frequency responses by means of Thevenin's theorem. The transient voltage is expressed as the sum of Fourier series of the steady-state voltages. The lightning surge overvoltages calculated by the proposed method are in satisfactory agreement with the transient solutions calculated by the EMTP technique, and the computation time and memory requirements are far smaller. Because the proposed method evaluates the lightning surge overvoltage only in terms of steady-state solutions, it is conveniently used to evaluate the effect of the circuit parameters of a substation in terms of ac theory and thus may be useful in investigating the relationship between bus length and overvoltage, in estimating the optimum location of an arrester installation, and so on.