Domains of ferroresonance occurrence in voltage transformers with or without damping reactors

This paper is aimed at investigating the circumstances under which ferroresonance is liable to occur in a 400 kV Gas Insulated Substation (GIS) equipped with inductive voltage transformers, and at establishing the efficiency of damping reactors connected to the secondary winding of these transformers in order to improve the damping of the ferroresonance or to avoid its appearance. The paper outlines the computational model. Various operational schemes liable to be driven into ferroresonance are taking into account. The ferroresonance occurrence domains, determined using the computational model, emphasize that the damping reactor efficiency depends on the value of the external serial resistor and on the various operational schemes.