Modelling of 132kV overhead transmission lines by using ATP/ EMTP for shielding failure pattern recognition

Abstract

Lightning overvoltage is the major cause of the transmission line interruption in Malaysia. It is the main reason that endangers the safety and reliability of transmission line system. The phenomenon is a dominant factor considered in designing substations and transmission-line insulation, therefore its investigation is important. This work modelled a 132 kV overhead transmission line for shielding failure pattern recognition by using ATP-EMTP software, as they are vital to the evaluation of lightning performance. The modelled transmission-line is divided into few parts: wires (shield wires and phase conductors), towers, cross-arms, insulator strings, tower-surge impedance and tower-footing resistance. The developed model is simulated with four different magnitudes of lightning-strike current on each phase conductor in order to investigate the shielding failure voltage pattern across the line insulation in the transmission line system. When the lightning- strike current is injected from upper phase to lower phase conductor, the magnitude of the maximum induced voltage across the insulator string at those phases has been decreased. On the other hand, as the magnitude of the lightning- strike current has been increased, the magnitude of the maximum induced voltage across the insulator string at each phase will be increased. Flashover occurs when the voltage induced across the insulator string at each phase is equal or exceeds the CFO voltage. These analyses have been done based on the waveforms obtained from the simulations on developed model.