The performance of lightning protection system on 275 kV transmission lines Siguragura-Kualatanjung, North Sumatra, Indonesia

The research work has been done to investigate and analyze the lightning protection system on 275 kV Transmission Lines Siguragura to Kualatanjung in North Sumatra, Indonesia. This transmission lines is located near the equator which is known as an area with a high lightning density. Lightning data used in this work derived from National Weather Office shown that the total cloud to ground lightning flashes is very high compare to another area around it. To give good shielding from lightning strikes this transmission lines used three overhead ground wires. The use of 22 pieces of porcelain insulator instead of only 18 pieces with the counterpoises grounding system and the installation of magenetic link to measure the peak current in every tower give the good performance against lightning strikes. But the damages due to lightning strikes were still reported, such as the damages at ground wire and arcing horns. The work were done by measuring the lightning strikes to the towers, analizing the shielding failure using electrogeometric concept and finite element method. The result shows that the shielding failure flash over rate is zero. The estimation of lightning performance calculated by Whitehead concept give the results of excellent grounding and shielding. However, by using the lightning data derived from the tropical area, such as the probability of lightning peak current and the field measurement measured by magnetic links shows the different results and it stated as good grounding and shielding performance only. The transmission lines with three overhead ground wire have given a significant results against lightning strikes compare to the use of only two overhead ground wire in the tropical region.