Optimization of neutral grounding reactor parameters-an analysis for a double circuit EHV line

In order to maintain power transmission reliability, application of single-phase switching (SPS) and auto-reclosing on EHV line is a common practice. However, in some cases, it is necessary to apply special means like neutral grounding reactor (NGR) to improve the conditions for secondary arc extinction for successful auto-reclosing. This paper presents importance of various parameters in optimization of NGR in a double circuit (D/c) EHV line. In case of SPS on D/c line, the secondary arc is maintained not only by the inter-phase coupling of the faulted circuit but also by the mutual coupling of the other healthy circuit. An empirical formula for NGR value of a double circuit line along with the methodology for its optimization is presented. Magnitude of secondary arc current also depends on the line length, power flow, source strength etc. Sensitivity of various parameters on secondary arc current has been demonstrated through EMTP study