CALCULATING CAPACITANCE FOR 500 kV DOUBLE CIRCUIT TRANSMISSION LINE WITH INVERTED PHASE SEQUENCE

Abstract

In defining electric field distribution under 500 kV traJ1§mission line, phase-groundcapacitance calculation plays a very important role. This paper presents the capacitancecalculation method for a special case: 500 kV double circuit transmission line with invertedphase sequence.Based on Maxwell's set of equations expressing the relation between phase potential andcharge of a "3 phases - ground" system, we could apply for a 500 kV double circuit transmissionline with vertical configuration of conductors and inverted phase sequence: A,-B,-C, vii C,-B,A,including the effect of two earth wires. So there will be eight equations showing the linkbetween the potential and the charge of phase conductors and shielding wires.Because of the inverted phase sequence, when transposing the phase sequence of twocircuits at the same time, the relative position between phases, phases to ground and phases toearth wires will be different, so we have to calculate the capacitance of all phases. This is quiteiifferent from the case of two circuits with the same phase sequence. After alterring, we willmake the above equations shorten and so we could define the phase capacitance that is the ratioof the charge per the potential of each phase respectively.With this result, then we could calculate the distribution of electric field under 500 kVdouble circuit transmission line with inverted phase sequence, compare with the case of twocircuits with the same phase sequence and raise the necessary recommendation to mitigate theeffect of EHV transmission line electric field on human and environment.