With the acceleration of social process, the users'demand to power distribution reliability and quality is increasing. Correspondingly, urban distribution network is also developing endlessly, and has formed'Closed loop connection, open loop operation'approach. When we need load transmission or lines maintenance, the traditional method is interrupt power supply first, then transfer the load. But this method has been unable to meet the need of users. For this reason, it requires closed-loop operation to transfer load, improve utilization and mutual supply without interrupting the power supply.During operation, because of the differences of network structures, line parameters and load. The steady-state current and impact current that produced by closed-loop operation may lead to line protection, even a wider range of power outage. Therefore, to avoid unnecessary breakdown or accident, it is necessary to analysis before closed-loop operation, computing the power flow and current of closed loop. Then proposed effective and practical measures to reduce the circulation is important to realize closed-loop operation effectively and smoothly.Based on the structure and characteristics of distribution network, this paper summarizes all aspects of the loop closing operation. Then establish corresponding model, based on the analysis of a variety of current calculation method in closed-loop network, proposed combine Newton-Raphson algorithm and superposition method to calculate the steady-state current in the closed-loop. The transient process is also analyzed in detail, deduce the formula of surge current and its relationship with the steady-state current by Thevenin's theorem and corresponding model.In this paper, the current and flow of lines in the closed-loop is also studied in detail. Derive current formula with network parameters based on typical closed loop, expressions of power flow, and the effects of voltage amplitude difference and phase angle difference on the power flow. And then analysis the reason of how the closed-loop current formed and the influence factors.Then combined with the equipment and parameters of distribution network, find out the adjustable factors of power flow and current, explore methods to reduce the closed-loop current.Finally, integrated to form a corresponding closed-loop current control strategy, conbine actual devices and characteristics of network and all the derived results, proposed measures to reduce the closed-loop current, formed corresponding control strategy of closed-loop current integrated, and the effectiveness and feasibility of the control strategy is verified. |