I 摘要 近年来，随着经济社会的发展，人们对配电网供电可靠性的要求日益增高。 国内配电网长期以来形成的“闭环设计，开环运行”模式无法满足部分地区对可 靠性的严苛需求。鉴于配电网合环能够进一步提升供电可靠性，本文对配电网合 环转供电操作和配电网合环运行相关问题进行了研究。 在配电网合环操作方面，提出一种配电网合环冲击电流计算方法，并推导了 较准确的非合环支路冲击电流解析计算公式。采用最佳频率法计算网络合环前后 最佳频率下的潮流，基于该潮流结果和戴维南定理，提出了利用现有潮流子程序 计算合环冲击电流衰减时间常数；提出了基于额定频率下合环前后的潮流结果和 最佳频率法计算获得的衰减时间常数，计算合环冲击电流及非合环支路的冲击电 流。 采用本文的方法、文献[23]的方法计算两个算例中的合环冲击电流，并与 PSCAD/EMTDC 暂态仿真的结果进行比较分析，验证了本文方法的实用性和有效 性。算例结果同时表明某些非合环支路的冲击电流比合环支路冲击电流要大，说 明本文提出的非合环支路冲击电流简化计算公式及其计算校验是非常必要的。基 于提出的方法开发了相应的配电网合环辅助决策软件，并将其应用于某地区实际 配电网的合环电流计算分析，对配电网合环操作具有较大的实用价值和指导意义。 在配电网合环运行方面，介绍了国内外中压配电网合环运行现状，以及馈线 合环方式、短路电流、继电保护及可靠性等方面的特点；综合考虑可靠性及经济 性，将配电网合环建设运行成本及停电成本计入优化目标，提出了配电网从开环 运行升级为合环运行的净收益模型；同时对以系统平均停电持续时间（SAIDI）为 主要指标的中压电缆线路可靠性评估简化模型进行了改进；探讨了配电网闭环运 行适用范围及实施难度。 以单回电缆为分析对象，对其由开环运行升级为合环运行后的可靠性及经济 性进行定性分析和定量计算，并对相关参数进行灵敏度分析。研究表明，对于经 济发达、负荷密度大、有分布式电源接入以及可靠性要求高的地区，在条件允许 的情况下，可考虑采用闭环运行方式（主要为来自同一母线的两馈线自环）；该运 行方式虽然可能增加供电公司的成本，但能够在提升供电可靠性的同时保证良好 的社会经济效益。 关键词:配电网；合环操作；冲击电流；合环运行；供电可靠性；经济性重庆大学硕士学位报告 英文摘要 II ABSTRACT In recent years, with the development of society and economy, the demand for distribution network reliability is rising. The closed-loop design, open-loop operation mode, which has been used for a long time for domestic distribution networks, cannot meet the stringent requirements on power supply reliability for some areas. Since the power supply reliability can be further improved by the closing-loop operation or closed-loop operation of distribution networks, some related problems are studied in this paper. In the aspect of loop-closing operation, a method of calculating the surge current from closing a loop is proposed; meanwhilea relatively accurate analytic formula for calculating the surge current of non-closing branches is deduced. With Thevenin's theorem and the power flow analyses before and after closing a loop being employed, the decay time constant is computed through the optimum frequency method. Based on the decay time constant and the power flow analyses under the rated frequency, the surge currents of closing loop branch and non-closing loop branches can be calculated. The proposed method and the method in reference [23] are used to calculate the surge currents for two examples. The results are compared with those from PSCAD/EMTDC transient simulation with the proposed method’s practicality and validity being shown. The results also show that the surge currents of some non-closing loop branches are larger than the current of closing loop branch, and thus it is very necessary to check the surge currents of non-closing loop branches. Based on the proposed method, an aided decision making software of closing a loop in a distribution network is developed. The software is applied to the closing loop current calculation and analysis in an actual distribution network, and is of good practical value and guiding significance. In the aspect of closed-loop operation, the domestic and abroad closed-loop operation status quo of medium voltage distribution networks are introduced, as well as some features of closing loop modes, short-circuit current, relay protection and reliability. With both of reliability and economy being considered, the construction, operation and outage costs of closed-loop operation in a distribution network is included in the optimization objective, and a net profit model of upgrading a distribution network from opened-loop operation to closed-loop operation is established; at the same time, a重庆大学硕士学位报告 英文摘要 III simplified SAIDI evaluation model of medium voltage cable feeders is modified with the System Average Interruption Duration Index (SAIDI) being regarded as a main index. The difficulties and applicable scopes of closed-loop operation are discussed. Regarding a cable’s upgrading from the opened-loop operation to closed-loop operation, the corresponding qualitative analysis and quantitative calculation of reliability and economy are performed, and the sensitivities of some related parameters are also analyzed. The study result shows: for the areas of developed economy, large load density, distributed generation and high reliability requirement, the closed-loop operation mode (mainly the one of two feeders from the same bus) can be considered for use with the conditions being satisfied; although the cost of a power supply company may become greater due to the using of closed-loop operation mode, the power supply reliability can be improved with the social and economic benefits being ensured. Keywords: distribution network; loop closing operation; surge current; closed-loop operation; power supply reliability; economy重庆大学硕士学位报告 目 录 IV 目 录 中文摘要..........................................................................................................................................I 英文摘要........................................................................................................................................II 1 绪 论......................................................................................................................................1 1.1 选题背景及意义 ....................................................................................................................... 1 1.2 国内外研究现状 ....................................................................................................................... 2 1.2.1 配电网合环转供电研究现状 ........................................................................................... 2 1.2.2 配电网合环运行研究现状 ............................................................................................... 4 1.2.3 配电网可靠性评估研究现状 ........................................................................................... 5 1.3 本报告主要工作............................................................................................................................. 6 2 配电网合环分析理论基础 ...........................................................................................8 2.1 配电网合环转供电基础 ........................................................................................................... 8 2.1.1 合环转供电方式 ............................................................................................................... 8 2.1.2 合环稳态电流计算方法 ................................................................................................. 10 2.1.3 合环冲击电流计算方法 ................................................................................................. 12 2.1.4 衰减时间常数计算方法 ................................................................................................. 13 2.1.5 合环电流对继电保护的影响 ......................................................................................... 15 2.2 配电网合环运行基础 ............................................................................................................. 16 2.2.1 合环运行实践................................................................................................................. 16 2.2.2 合环运行方式的特点 ...