Analysis on Three-Phase Current Unbalance in Triple-Circuits of 500 kV Transmission Lines From Changzhi to Jiu’an in Shanxi Province

To investigate the cause of three-phase current unbalance of triple-circuits of 500kV transmission lines from Changzhi to Jiu’an in Shanxi province thoroughly and optimize the renovation scheme,using electromagnetic transient program PSCAD and structural model of the transmission lines different conductor arrangements were simulated and the optimal renovation scheme was recommended,and satisfied renovation effects were achieved.It was discovered from both simulation results and renovation process that for non-transposed double-circuit transmission lines on the same tower,within the 36 kinds of conductor arrangements the minimum current unbalance could be attained by six kinds of reverse phase sequence conductor arrangements and the current unbalance degrees of the six reverse phase sequence conductor arrangements are basically the same;however under the parallel operation of non-transposed double-circuit transmission line on the same tower with incomplete-transposed single transmission line,due to the affection of the single transmission line there were obvious differences among the six renovation schemes adopting reverse phase sequence conductor arrangements,thus there was the optimal one that could be selected.