Impact Of Split Factor Value On The Safe Design Of Substation Earth

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Martin Toi Shao Kiat
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Earthing system is an important role for every substation. it protects the equipment and the safety of personnel work in the substation during fault occur or lightning strike. To design a safe and economical earth grid, it is necessary to calculate the distribution of fault current in a substation. Split factor is a main consideration when design a safe and economical earth grid. In this study, a substation earth grid was designed by using CDEGS and carry out in MALT. The energized fault current is 5000A and varied into 100%, 75%, 50% and 25% to investigate the impact on safety level of the substation. There are 2 type of earth grid was designed and 3 scenarios were carried out by the both type of earth grid. The first earth grid consists of 7 parallel conductors in row and 9 parallel conductors in columns. Second earth grid consists of 11 parallel conductors in row and 13 parallel conductors in columns. Both of the earth grid conduct with 354Ω-m, 1000Ω-m and 3000Ω-m resistivity of soil surface layer. Result indicated that 25% of fault current flow into second type of earth grid in three scenarios are safe. Although substation hard to meet safety criteria while the resistivity of soil surface layer is high.
Split Factor , Touch Voltage , Step Voltage