Single-Phase Switching Parameters for Untransposed EHV Transmission Lines

Single-phase switching compensation schemes are presented and analyzed for untransposed EHV transmission lines having one, two or three shunt reactor banks. For this purpose modified and simple four-legged shunt reactor banks are utilized. A general method is developed to optimize the neutral reactor values in order to minimize the secondary arc current for different arrangements of the modified and simple four-legged reactors. As an example, a large range of 765kV lines is used and single-phase switching parameters are obtained and analyzed for different ratios between the capacities of simple and modified reactor banks. The optimum neutral reactances as well as the secondary arc current, recovery voltage and neutral reactor voltages are presented as functions of the compensation factor which is varied from 0.6 to 1.0.