中压配电网中性点接地方式研究与决策

发布时间：2018-04-03 03:15

本文选题：中性点接地方式　切入点：可靠性概率模型　出处：《重庆大学》2014年硕士论文

【摘要】：近年来，中压配电网飞速发展，电缆覆盖率大幅增长、网架结构不断增强、自动化程度日益提高、新能源广泛接入、新型故障选线技术的研发应用等，导致了中压配电网的中性点接地方式多样化，如何因地制宜的选取中性点接地方式对中压配电网的安全稳定运行具有重要意义。中压配电网中性点接地方式与供电可靠性、继电保护、过电压防护、通讯干扰及电气安全等密切相关，其选取方法应综合考虑上述因素，以保障人身、设备安全以及系统运行的可靠性和稳定性。本文通过对比了国内外中压配电网中性点接地方式的运用现状，分析了不同中性点接地方式下的单相接地短路故障特性，建立了相应模型计算不同条件下的故障电流、工频过电压及间歇性电弧接地过电压，得出了各中性点接地方式下故障电流及过电压的差异取决于单相接地故障时不同中性点接地方式对零序网络中零序阻抗的贡献。此外，对不同中性点接地方式下的安全防护措施及关键性问题进行了研究，提出了一种保证零序电流保护灵敏、可靠动作，过电压不超过一定范围以及最大故障电流在安全规范要求以内的多因素中性点电阻值选取方法；分析了影响消弧线圈接地系统选线准确率的因素以及各种选线方法的优缺点。建立了中压配电网不同中性点接地方式下线路的可靠性概率模型，对比分析计及、不计选线不准确率对概率模型的影响，以辐射型网络为例，评估了各中性点接地方式下、不同电缆比例时的配电网可靠性水平。基于上述可靠性评价结果，提出了一种综合可靠性、安全性及经济性因素的中压配电网中性点接地方式决策方法。该方法将不同中性点接地方式下配电网的可靠性评价与安全性防护及建设运行成本相结合，通过全寿命周期成本最优或可靠性水平最高为备选条件来实现中性点接地方式的决策，并通过算例结果验证了该决策方法的可行性及有效性，为中压配电网中性点接地方式的选择提供了决策依据。对含分布式电源(DG Distributed Generation)的新型中压配电网，针对单台DG及多台DG接入的情况分别建立等值模型，分析了DG并网变压器接地方式、接入容量及位置不同时，对配电网各中性点接地方式在发生单相接地故障时零序电流保护的影响，，并通过仿真计算及分析，寻求DG并网变压器与配电网主变中性点接地方式的配合原则。
[Abstract]:In recent years, with the rapid development of the medium voltage distribution network, the cable coverage has increased dramatically, the network structure has been continuously enhanced, the degree of automation has been increasingly improved, new energy sources have been widely connected, new fault line selection technology has been developed and applied, etc.It leads to the diversification of neutral grounding mode in medium voltage distribution network. How to select neutral grounding mode according to local conditions is of great significance to the safe and stable operation of medium voltage distribution network.The neutral grounding mode of medium voltage distribution network is closely related to the reliability of power supply, relay protection, over-voltage protection, communication interference and electrical safety.Equipment safety and system operation reliability and stability.In this paper, the current situation of neutral grounding in medium voltage distribution network at home and abroad is compared, and the characteristics of single-phase earthing short circuit fault under different neutral grounding modes are analyzed, and the corresponding models are established to calculate the fault current under different conditions.The power frequency overvoltage and intermittent arc grounding overvoltage are obtained. It is concluded that the difference of fault current and overvoltage depends on the contribution of different neutral grounding modes to zero-sequence impedance in zero-sequence network.In addition, the safety protection measures and key problems under different neutral grounding modes are studied, and a new method to ensure the sensitive and reliable operation of zero-sequence current protection is proposed.The methods of selecting the resistance value of multi-factor neutral point within a certain range of overvoltage and the maximum fault current within the requirements of safety specification are analyzed, and the factors affecting the accuracy of line selection of arc-suppression coil grounding system are analyzed, as well as the advantages and disadvantages of various methods of line selection.The reliability probability model of middle voltage distribution network with different neutral grounding modes is established. The influence of different neutral grounding modes on the probabilistic model without considering the accuracy of line selection is compared and analyzed. Taking the radiation network as an example, the neutral grounding modes are evaluated.Reliability level of distribution network with different cable ratio.Based on the above reliability evaluation results, a decision method for neutral grounding mode of medium voltage distribution network is proposed, which integrates reliability, safety and economic factors.This method combines the reliability evaluation of distribution network with safety protection and construction operation cost under different neutral grounding modes.The decision of neutral grounding mode is realized by the optimal life cycle cost or the highest reliability level, and the feasibility and effectiveness of the decision method are verified by an example.It provides a decision basis for the selection of neutral grounding mode in medium voltage distribution network.For a new type of medium voltage distribution network with DG Distributed generation (DG Distributed generation), the equivalent models of single DG and multiple DG connections are established, and the grounding mode of DG grid-connected transformers, the different access capacity and location are analyzed.The effect of neutral grounding mode on zero-sequence current protection in single-phase grounding fault in distribution network is discussed. Through simulation calculation and analysis, the coordination principle between DG grid-connected transformer and neutral grounding mode of main transformer in distribution network is sought.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM862

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