Optimum damping resistance of potential transformers for mitigating ferro-resonance in gas insulated substations

Different methods are developed for mitigation of ferro-resonance in high-voltage gas insulated substations (GISs). The main components, which have impacts on probability of occurrence of ferro-resonance, are grading capacitance of circuit breakers (CBs) and internal loss of potential transformers (PTs). However, by using active or passive damping resistance in the secondary of PTs, the probability of occurrence of ferro-resonance can be decreased substantially. It is worth mentioning that the thermal limitations of PTs restrict us to dissipate a lot of energy in the damping resistance. Therefore, in this paper, both thermal and electrical aspects of ferro-resonance are considered and modeled to obtain the optimum value of damping resistance for mitigation of ferro-resonance. The proposed model to find the optimum value is based on robust optimization programming. The proposed model is tested and validated on two GISs in Iran.