Flashover and Back-Flashover Analysis with Lightning Strokes of 69 kV and 24 kV Lines in Thailand Using ATP/EMTP

Lightning is the principal source of disturbance in power system leading towards outages and damage of expensive equipment in the electrical power network. Induction of disastrous voltages across string insulators from the lightning that causes flashovers and back flashovers have been the major study in recent researches. Efficient parameterization of lightning and it is associated with behavior provides a significant knowledge towards successful operation of the electrical network. Therefore, this work studies the effects of flashover and back flashover affected by negative lightning (single and double) strokes in the operation of 69 kV sub-transmission line and 24kV distribution line of Metropolitan Electricity Authority, Thailand. Seven poles spanning 24 km were considered in this study. Lightning was initiated at the vertex of the fourth pole and mid-span of the third and fourth pole, and investigations were carried out by lightning magnitude and multiplicity when it hits an overhead ground wire (OHGW) and phase A of the 69 kV line by using ATPDraw. Results showed that negative lightning stroke of -34 kA and above could induce disastrous voltages across string insulators that leads to back flashover and flashover when hits at the top and mid-span of OHGW and phase conductor respectively. Power failure in 69 kV may cause double failure to the network since it is the main power source of 24 kV line. Consequently, a double failure may direct towards reduced reliability and extra maintenance cost of catastrophically damaged line insulators. Therefore, the concept of flashover and back-flashover can help to improve the lightning performance of MEA power lines.