Challenges in field implementation of controlled energization for various equipment loads with circuit breakers considering diversified dielectric and mechanical characteristics

The close coordination between circuit breaker (CB) characteristics and behavior of equipment to be switched plays key role in achieving desired mitigation results during controlled switching. In this respect, usually, controlled closing is found to be more challenging compared to controlled opening. This paper presents key aspects in context to performance assessment of a CB during controlled energization of various equipment loads based on its mechanical and dielectric characteristics. The energization target may vary from CB gap voltage zero to peak depending upon the behavior of the equipment to be switched. In this context, the procedure of evaluating energization targets for various power system loads with diversified design and connection configurations have been elaborated. Furthermore, the way to analyze suitability of CB characteristics for achieving a range of energization targets having different closing speed and time scatter; especially breakers with slow closing speed have been discussed in detail. The challenges due to operating time scatter and inter phase coupling for transformers and uncompensated transmission lines have been analyzed in conjunction with field results. Finally, comparison of mitigation effects obtained during energization of shunt reactor with dissimilar CB operating characteristics on an existing 400 kV Indian transmission network has been presented.