小电流接地方式对电力系统故障的影响

发布时间：2018-09-17 16:47

【摘要】：小电流接地系统是国内外非常流行的一种接地系统。目前常见的小电流系统都是以接地方式的不同而作区分的,而最常使用的接地方式主要有经电阻接地、经消弧线圈接地以及不接地三种。目前我国的小电流接地系统主要使用于3-66kV的电力系统中。这主要是因为小电流接地系统在遭遇故障的时候仍然能维持一段时间的正常运行,因此被广泛使用。我国的6~66kV配电网电力系统多属于小电流接地系统,一般采用中性点不接地或者中性点经消弧线圈接地的工作方式,因其发生接地故障时,流过接地点的电流小,又称中性点非有效接地系统。接地故障是指由于导体与地连接或对地绝缘电阻变的小于规定值而引起的故障。根据电力系统运行部门的故障统计,由于外界因素(如雷击、大风、鸟类等)的影响,配电网单相接地故障是配电网故障中最常见的,发生率最高,占整个电气短路故障的80%以上。当发生单相接地故障时,由于不能构成低阻抗的短路回路,接地电流很小,故称为小电流接地系统。它的优点在于发生单相接地故障时多数情况下可以自动熄弧并恢复绝缘。当线路发生永久性单相金属接地故障后,三相系统的线电压仍然是对称的,大小与相位并不变化,但系统的接地相对地电容被短接,对地电压都变为零。为防止另一相在接地而引起两相短路甚至三相电路,因而必须限制一定时间内排除单相故障。本文致力于解决小电流接地系统在遭遇故障的时候减小对电力系统的损害问题。通过深入分析系统发生故障的原因,从而在源头上找到避免故障发生的办法。为此,计划进行下述工作:(1)研究中性点接地各种方式的特点。(2)进行小电流单相接地系统的故障分析。(3)电力系统短路故障分类与计算。(4)进行小电流接地系统故障仿真分析。
[Abstract]:Low current grounding system is a very popular grounding system at home and abroad. At present, the common small current systems are differentiated by different grounding modes, and the most commonly used earthing methods are mainly through resistance grounding, arc suppression coil grounding and non-grounding. At present, the small current grounding system in China is mainly used in the power system of 3-66kV. This is mainly due to the low current grounding system can still maintain normal operation for a period of time in the event of failure, so it is widely used. The power system of 6~66kV distribution network in our country mostly belongs to the small current grounding system. Generally, the neutral point is not grounded or the neutral point is grounded by the arc-suppression coil, because the current passing through the connection place is small when the grounding fault occurs. Also called neutral point non-effective grounding system. Grounding fault refers to the fault caused by the connection of conductor to ground or the change of insulation resistance to ground less than the specified value. According to the fault statistics of power system operation department, because of the influence of external factors (such as lightning strike, strong wind, bird and so on), the single-phase grounding fault of distribution network is the most common fault and the highest incidence. It accounts for more than 80% of all electrical short-circuit faults. When a single-phase grounding fault occurs, it is called a small current grounding system because it cannot form a short circuit with low impedance and the grounding current is very small. Its advantage is that it can automatically extinguish the arc and restore the insulation when the single-phase earth fault occurs. After the permanent single-phase metal grounding fault occurs, the line voltage of the three-phase system is still symmetrical, and the magnitude and phase of the system are not changed, but the grounding capacitance of the system is short-connected and the voltage to the ground becomes zero. In order to prevent the other phase from causing two phase short circuit or even three phase circuit in grounding, it is necessary to limit the single phase fault within a certain time. This paper is devoted to solving the problem of reducing the damage to the power system when the small current grounding system is in trouble. Through in-depth analysis of the causes of system failures, to find ways to avoid failures at the source. Therefore, the following works are planned: (1) study the characteristics of neutral grounding modes; (2) carry out fault analysis of single-phase earthing system with small current; (3) classify and calculate short circuit faults of power system; (4) carry out fault simulation analysis of low current grounding system.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM862

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