Application of Line Surge Arresters for Switching Over-voltages in UHV Transmission Systems

Switching Overvoltages (SOV) are critical for systems operating at Ultra High Voltage (UHV) level. Pre-insertion resistors (PIR) are usually used to suppress the switching overvoltages in UHV systems. PIR are effective in suppressing SOV’s, but their shortcomings prompt utilities to explore other protection schemes. In this paper, the application of Line Surge Arresters (LSA) to suppress switching over voltages is studied. The statistical overvoltage analysis is carried out for a typical UHV system to compute the highest overvoltage magnitudes. The location and number of LSA’s to be placed along the transmission line are decided based on the overvoltage profile along the line, observed during switching operations. The switching impulse withstand values of the equipment are calculated for proposed non-gapped line arrester arrangements and also compared with the withstand values for conventional system. The energy absorbed by the LSA’s when placed along the transmission line is also observed. The simulations are performed using Electro-Magnetic Transient Program for the 1200 kV Indian transmission system. The results of this study show that the LSA’s can be considered an alternate protection measure to suppress SOV’s in a UHV system.