【作者】 周卓敏；

【导师】 彭建春； 彭高辉；

【作者基本信息】 湖南大学 ， 电力系统及其自动化， 2007， 硕士

【摘要】 本文根据目前长沙城区10kV配网的特点,结合实际情况,对长沙城区10kV配网现有接地方式(中性点经消弧线圈接地方式)及其使用的配套装置进行分析,发现部分消弧线圈容量已经不能满足实际要求;配套的小电流选线装置选线准确率低;消弧线圈微机控制装置性能不稳定,使自动跟踪补偿线圈的优势显示不出来。随着长沙配电网电容电流的不断增长,中性点经消弧线圈接地方式的弊端也突现出来,具体表现为系统发生单相瞬时接地故障时,电弧不易熄灭,从而演变成相间短路,甚至多线短路等故障。通过分析研究,认为应将长沙城区10kV配网部分(电缆占主导的系统)中性点经消弧线圈接地方式改为中性点经小电阻接地方式,其优点是当发生单相接地故障时,由继电保护动作切断故障,从而保证配网的安全运行。本文对中性点经小电阻接地系统的一次设备和继电保护设计进行了阐述,并以黎托变电站、广电变电站为例进行了设计。即使小电阻接地方式优点显著,但由于架空线路易发生树枝碰线等瞬时接地故障,无论接地故障是永久性还是非永久性的,线路断路器都会跳闸,使线路跳闸次数大大增加,降低了供电可靠性。分析论证得出城郊变电站架空线路占主导,不宜采取中性点经小电阻接地的方式。所以在长沙城区10kV配网应采用两种接地方式共存。在重负荷的长沙城区(电缆线路比重大的变电站),将10KV配网经消弧线圈接地系统改为中性点经小电阻接地,在城乡交接地域的变电站(以架空线路为主导)可以考虑使用新型KD-XH配电网智能化快速消弧系统,有利于长沙城区10KV配网的安全、可靠运行。更多还原

【Abstract】 Under overall investigation on 10kV distribution network in Changsha district we notice that current neutral grounding mode via arc suppressing coil would not meet the demand sufficiently in three aspects: some of the arc suppressing coil failed to reach the capacity for practical application; supporting selected line equipment with small current ran under low accuracy; insufficient arc controller disturbed the full function of automatic tuning compensation arc suppression coil. Among practical accidents related to the incapacity of the grounding mode the biggest problem is that when one-phase-to-ground faults are detected arc extinction is difficult to complete and interface short circuit even poly-phase short circuit occurs instead. Therefore we try to introduce a novel neutral grounding mode via small resistance in distributing system which applies relay protection to cut off single-phase line faults for minimal electrical hazards.This paper describes the design and implementation of neutral grounding equipment and relay protection schemes. Lituo and Guangdian power stations are employed to illustrate the proposed ideasOverhead line trends to produce instantaneous ground faults caused by contact of branches and other aerial objects. Once such faults happen the reliability of distribution network would be damaged heavily because cut-off conductors in supporting neutral grounding system would react consequently under both permanent and impermanent fault conditions. Therefore we conclude from comprehensive investigation on suburban distribution network which be covered up mainly by 10kV overhead line that neutral grounding via small resistance fail to provide substantial ground-fault protection and insulation and continue to discuss the alternative approach for overhead line grounding protection in the paper based on the conclusion.On the whole, we try to propose innovative grounding solution for urban and suburban distribution network in this paper. Grounding mode via arc suppressing coil in heavy-load 10kV urban distribution network would be recommended to be replaced by neutral grounding mode via small resistance. On the other hand suburban overhead line network adopt KD-XH intelligent fast arc suppressing coil for grounding solution. We hold rational reasons to believe that the combination of grounding modes suitable for different distribution network would improve the power utilization in Changsha district largely.更多还原