To assess the performance required for the 765 kV equipments and insulation coordination of the 765 kV systems, an exhaustive Electromagnetic Transient study was performed.

This study covered the several aspects such as continuous power frequency overvoltage, temporary overvoltage, switching overvoltage & lightning overvoltage. Statistical switching study is done to find the maximum overvoltages arising in the system. These overvoltages were reduced using surge arrester, Pre insertion resistance & controlled switching.

Various simulations are done to ascertain the value of energy stresses on the surge arrester. Optimization of neutral ground reactor of line reactors is also done for minimizing secondary arc current for the successful Single Phase Auto Reclose.

For all the simulation ATP (Alternative Transient Program) is used. All models drawn in ATP-Draw version 3.7p2 provided by SINTEF Energy Research, Norway, vide personal license No. (IEU086) (ATP-India user group). Insulation coordination of equipments is done based on IEC & IEEE standards for insulation coordination.