Novel approach to study and prevent failure of an electromagnetic voltage transformer due to sustained overvoltage on switching

Abstract

The failure of an electromagnetic voltage transformer (EMVT), connected to a 220 kV substation, due to steady state ferroresonant overvoltage on switching and a numerical analysis to support the results of the field test have already been reported by Aggarwal et al. in 1981. However, the harmonic balance method suggested before is too involved to tackle such a nonlinear problem and failed to confirm all the test results. The present paper aims at developing a systematic analytical approach for an in-depth investigation of the effect of steady state ferroresonant over-voltage on an EMVT. The analytical approach presented confirms all the field test results and shows that connection of resistive load across the secondary of the EMVT will not serve as a measure to prevent its failure, as tried by the previous authors. A simple and elegant method is suggested here as a remedial measure.