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Adjustment Method of Insulation Level Difference between 10kV Overhead Line and Distribution Transformer

The single-phase installation method of 10kV overhead bare conductor with parallel gap can effectively improve the lightning resistance level of the line, but it further expands the difference in insulation level between the line and the equipment, and the power distribution equipment is more vulnerable to damage. It is not economically feasible to improve the insulation level of power distribution equipment and the current capacity of the zinc oxide arrester (MOA) at the front end of the equipment, this paper adopts the method of installing coupling ground wire at the end of 10kV line to solve this problem. The shunt principle of the coupled ground wire is studied, and it is considered that the number of poles and the grounding resistance of the poles are the main factors that affect the shunt effect. A 10kV overhead bare-conducting line overvoltage simulation model under the parallel gap single-phase installation mode is established. The calculation results show that in a typical configuration of 10kV overhead lines, when the induction point of the induced lightning is 4 base poles before the distribution transformer, the maximum overcurrent energy of MOA passing through high voltage side of distribution transformer exceeds the threshold of safe operation; at this time, the coupling ground wire is installed on the two base poles before the distribution transformer, and the poles and towers do not need to be grounded to limit the flow of the MOA on the high-voltage side, it can limit the overcurrent amplitude and thermal charge transfer value of MOA flowing through the high voltage side to below the safety threshold, the maximum reduction is 69.4% and 83.5%, respectively. The proposed method plays an important role in reducing the failure rate of power distribution equipment and maintaining the safe and stable operation of the distribution network.