【作者】 宋云东；

【导师】 苑舜； 蔡志远；

【作者基本信息】 沈阳工业大学 ， 高电压与绝缘技术， 2010， 博士

【摘要】 随着我国经济的快速发展,配电网建设不断增加,城市内线路走廊用地越来越少,征地所需费用也越来越昂贵,所以电缆敷设成为线路建设的主要方式。同时为了满足城市环境美化及供电可靠性的需要,城市配电线路也由原来的架空线路部分或者全部改为地下电力电缆线路。随着电力电缆在城区配网中所占比例越来越大,导致配电网容性电流不断增大,在单相接地故障发生时使故障电流增大,给设计部门及实际运行单位都带来了一定的困难。因为单相接地保护方式存在多种形式,而且对单相接地保护方式的选择一直存在较大争议,所以本文主要研究单相接地故障保护方式选择依据及其故障保护方式的综合评价方法,为设计和运行部门提供理论依据和参考。通过对电缆网存在的不同类型故障进行分析,得到不同类型故障产生的原因,并对电缆绝缘破坏到电缆发生燃烧的过程进行理论研究。在上述研究的基础上建立了永久性接地故障模型和弧光接地模型;使用受控制开关导通与关断单相接地电弧,及可变电阻模拟电弧电阻,基于电弧故障消失或转化的判据建立了电缆击穿至燃烧阶段的故障模型。模型的建立为单相接地故障计算分析提供了理论基础,且首次推导出电缆基于热因素的电弧烧毁模型,为保护方式响应时间对单相接地故障控制效果分析的计算打下基础。在电缆网故障模型建立的基础上,对影响单相接地故障分析的不同因素进行随机组合计算。经过分析上述计算结果得到了电缆网电容电流、接地电阻、接地点位置及接地保护方式对系统运行的影响程度。经过对比不同工况下系统的电压与电流,得到单相接地故障暂态过程中性点经小电阻接地保护方式最优,稳态过程基于分流装置保护方式最优的结论。在大量单相接地故障计算结果的基础上,建立了基于IAHP的单相接地故障综合评价方法。主要对不同电缆网单相接地故障保护方式进行分析,得出判别单相接地故障保护方式的判据;在建立综合评价层次结构的基础上,建立了层次决策表,利用两两比较法得到判断矩阵,经过对判断矩阵的一致性校验,求得总目标的综合权重,最后通过排序得到关于不同保护方式的综合评价权重。在此首次将IAHP应用于单相接地故障保护方式的评价方法,而且该方法可有效避免人为因素导致的误差,达到了准确评价故障保护方式的目的,从而为具体电缆网故障保护方式选择提供依据。为了验证不同保护方式对单相接地故障的控制效果及熄灭电弧的特性,搭建了基于380V供电系统的模拟实验台。系统中的元件参数均为采用10kV设备等值简化得到,试验证明实验平台可有效模拟10kV配电系统。采用PIC控制系统实现了对接地故障开始时刻及保护方式响应时间的准确控制。在模拟实验台上的试验证明了仿真计算结果及综合评价结果的正确性,验证了保护方式对单相接地故障控制效果及熄灭电弧的作用。在实际变电站进行了基于分流装置故障保护方式的接地试验,结果证明该接地保护方式在单相接地故障时有消弧和抑制过电压的作用,验证了基于IAHP综合评价结果的正确性。更多还原

【Abstract】 With the economy developing rapidly, distribution network construction increases and land for line-corridors in the city is getting less and less, land costs are increasingly rising, so laying of cables become the main ways for line construction. Meanwhile, in order to meet the needs of the urban landscaping and power distribution reliability, urban distribution lines have been converted from the original overhead lines into underground power cable lines completely or partly. With the proportion of power cable in urban areas distribution network increasing quickly, capacitive current of distribution network is increasing gradually, so that fault current increases when single-phase ground fault occurs, and some difficulties have been brought to the actual operation units and the design departments to some extent. Because there are various kinds of single-phase protection ways, and a big controversy arises on the choices about single-phase protection way, in the paper, the methods of synthesis evaluation on the single-phase protection ways and the approaches to protecting it from fault were formulated, which was expected to provide a theoretical basis and reference to the actual operation units and the design departments.The causes resulting in different faults were obtained through analysis of different types fault models in cable networks, and the processes of cable insulation damage to burn was studied. Based on the study above, a permanent ground fault model and the arc grounding model were formulated; using a controlled switch turn-on and turn-off single-phase ground arc, and using variable resistor simulated arc resistance, the arc faults were established during the cable breakdown to burning based on the criterion of the fault disappearance or transformation. The model establishment provided a theoretic basis for calculation and analysis on single-phase ground fault, and the first cable arc burnout model based on thermal factors was derived, which was a basis for the calculation of the single-phase ground default control effect against protection methods response time.Based on the establishment of the cable network fault models, the factors affecting single-phase ground fault analysis were calculated in random combinatorial way. After analyzing the results of the cable network capacitive current, grounding resistance, ground point location and grounding protection methods on the degree of influence system operation have been obtained. After comparing the system voltage and current under different conditions, it’s found that the neutral grounding via low resistance mode protected systems best during transient process of single-phase ground fault, while during steady process based on shunt devices protected systems best.A large number of single-phase ground fault calculation results were used to establish a single-phase ground comprehensive evaluation based on IAHP. Through the analysis on different cable networks single-phase ground fault ways, the criterion of distinguish single-phase ground fault protection ways were obtained; based on establishing hierarchy structure of comprehensive evaluation, hierarchical decision-making table was set up, and judge matrix was obtained by using pairwise comparison, and consistency of matrix should be checked, and the comprehensive weight of overall goal was obtained, at last, the comprehensive evaluation weight of each protection way was obtained by collating. IAHP was applied to single-phase ground fault protection methods as an evaluation way for the first time in this paper, which can effectively avoid the errors caused by human factors and achieve fault protection approach purpose accurately and provide reference for the selection of protection means to specific cable network.In order to verify different protection methods on the control effects of single-phase ground fault and the characteristics of arc extinguish, simulation experiment platform was structured based on 380V power system. System component parameters were obtained through simplifying to be equivalents based on 10kV equipment, and the experiment proved that the experimental platform could effectively simulate 10kV distribution system. PIC control system was used to control the earth-fault beginning and protection mode response time accurately. The simulation experiments on the platform proved that the simulation results and the comprehensive evaluation results were correct, and verified the protection methods for single-phase ground fault controlling effects and extinguishing arc role.Grounding tests based on streaming device fault protection methods carried out in a substation, the results of which proved that the grounding protection methods played the role of arc-suppression and suppression over-voltage when single-phase ground fault occurred and verified the results of comprehensive evaluation based on IAHP correctness.更多还原