Investigation of performance of ferroresonance suppressing circuits in coupling capacitor voltage transformers

In order to restrain ferroresonance in coupling capacitor voltage transformers (CCVT), three kinds of ferroresonance suppression circuits (FSCs): the resonant type, the fast-saturation reactor type and electronic type which are connected to secondary side of CCVTs, are proposed in this paper. Frequency domain analyses, for voltage ratio magnitude, are carried out for CCVTs to obtain preferable FSC. Furthermore, using surge suppressors such as metal oxide varistors (MOV) to improve the performance of the FSCs is investigated. Time domain simulations demonstrate that ferroresonance can be cleared in few cycles in presence of FSCs. The Electromagnetic Transients Program (EMTP) is used for modeling and fine-tuning the FSCs.