The Effect of Grounding Resistance About Back Flashover on 150 KV Tranmission Network in Main Station of Sungguminasa - Tallasa (Makassar)

Abstract

Lightningsurge on transmission network is a natural problem that affecting electricity voltage. This impact on the occurrence of equipment damages as result of back flashover. Back flashover causes an impulse wave due to the increase of voltage on the transmission and has a large grounding resistance value. There has been a disturbance in the transmission system SULSELRABAR causing black out on Tuesday, January 19th, 2016 at 14:13 pm. The disturbance occurred along with the rain and strong winds accompanied by lightning which caused the load loss of 746 MW. The research was conducted to determine the occurrence of direct lightning strikes on each tower, the effect of grounding resistance to back flashover on150 kV transmission network in main station of Sungguminasa - Tallasa, using modeling simulation of peak menara transmission network 150 kV in main station of Sungguminasa - Tallasa with software ATPDraw (Alternative Transient Program). The simulation results depicting one of the phase wire reach the peak current of 359.89 MA. In this condition occurs disruption that causing the impulse voltage and back flashover with disturbance current 22.65 kA. The large of grounding resistance has an average voltage exceeding the capacity limit from 1001.54 kV to 1042.31 kV. Based on the calculation, the impulse voltage obtained is 5.271 MV close to simulation result of ATPDraw(Alternative Transient Program) by 4.530 MV. The calculation of the current wave when there is lightning disturbance in the transmission line with a peak current of 60 kA and the wave front time of 1 set, obtained the highest value that is on the tower 39 the grounding value of 5.4 Ω, the grounding value obtained reflection coefficient of -0.937 and insulator voltage at 957.036 kV, the results of this research held the measurement of tower 39 using Megger Det4tcr and obtained the grounding value on the tower feet of 12.22 and 9.97 ohm. What makes this case interesting is that the installation is located in a wet-sand soil type, undertaken decrease grounding value of 39 of parallelization methods by adding 2 copper rods (arde) 5/8 inch diameter in 4 meters long and the addition of mixture of carbon and NaCl, the result of was able to reduce the magnitude of grounding resistance is 0.78 ohm, close to the calculation results of parallelization method is 0.0864 ohm.This method is more accurate because the disturbance of back flashover can be avoided by lowering the high grounding value due to lightning strikes and protecting other equipment, can be used in long-term, inexpensive and simple, very suitable applied of wet soil