Closed-Loop Low-voltage Distribution System Design, Implementation And Reliability Analysis

As the terminal of power system, low voltage distribution network’s operation state directly impacts user experience. Once a fault occurs, a significant influence will be imposed on users’terminal due to the widely used open radial structure of low-voltage (LV) network;Even with ring structure, the LV distribution network usually operated as open radial network, making it difficult to solve the short time outage problem. Currently, fault locating and power recovering rely on on-site operation due to the low automatic degree of LV distribution network, which takes long time to fix problems and has great effect on important loads, including high building elevator, firefighting load et al. With the development of economy, traditional LV distribution network cannot keep pace with the requirements for high reliability of power supply to users. In summary, a new way of LV network to supply power has practical significance.The closed-loop operation mode of LV distribution network is discussed in this paper, aiming at the improvement of reliability. Based on characters of closed-loop structure, protection needed, communication, monitor software and other essential technology, the differences between closed-loop operation of LV distribution network and media voltage distribution network is studied, as well as the effects of LV distribution network closed-loop operation on media network. Based on smart terminal unit(STU), the components as well as suitable protection of closed-loop LV system are introduced. A monitor software is developed, whose communication part is based on IEC60870-5-103 communication protocol. What’s more, its monitoring interface part is based on Microsoft Visio secondary development that can provide powerful image process and management ability. The impacts of closed-loop structure on reliability is studied. Based on ASP.NET and jQuery Scripting Framework, a web application to manage the LV distribution systems’reliability data was coded, whose equipment foundation is realized by STU and data acquisition pathways is provided by communication networks.