Effect of Externally Gapped Line Arrester Placement on Insulation Coordination of a Twin-Circuit 220 kV Line

Application of externally gapped lightning arresters (EGLAs) to a twin circuit 220 kV transmission line was simulated using Alternative Transients Program/Electromagnetic Transients Program. The lightning current to the tower top as well as to phase conductors was estimated using the electrogeometric model. Increasing the number of phases on which EGLAs were installed in one circuit reduces the likelihood of back flashover. Installing EGLAs on the three phases of one circuit has two advantages, viz., 1) eliminating double circuit outages and 2) preventing lightning-induced back flashovers for strikes to the tower top ≤ 200 kA. However, EGLAs on one circuit cannot improve lightning performance related to the shielding failure when the unprotected circuit is hit. EGLA duty varied little with the number of phases on which EGLAs were installed, which indicates that the required EGLA rating is unlikely to depend on the number of phases on which EGLAs are installed.