There has been tremendous growth in the power industry in Indiaduring the last five decades. Presently, more than 35000 circuitkilometers of 400 kV and above transmission lines are transmitting bulkpower within the regional grids and also from one regional grid toanother regional grid. As India is a vast country with area about 3million sq.kms, the 400 kV transmission lines are quite long of theorder of 250 to 350 kms. Most of the transmission lines are on doublecircuit towers. For maintenance of transmission lines, shut down of boththe circuits is not normally available. Maintenance of these doublecircuit lines with one circuit live has to be done under induced voltageconditions. However, very high level of induced voltage of the order of23-82 kV under various operating conditions persist for a 300-350 kms.Long 400 kV double circuit line connected with 63 MVAr shunt reactors atboth ends. This paper describes how we have been able to control theinduced voltage to a very low level of 8-10 kV. Further, design ofportable earthing equipment and earthing schemes suitable for suchmaintenance work under these conditions with utmost safety are alsodescribed in the paper
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