大连66kV系统三相电压不平衡问题分析及处理

发布时间：2018-02-26 21:05

本文关键词： MATLAB仿真三相电压不平衡度消弧线图　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：电力系统在正常运行及事故状态下均会发生三相电压不平衡,本文主要分析的是系统在正常运行时发生的三相电压不平衡现象。阐述了系统三相电压不平衡对发电、供电、输电及配电环节中各种用电设备造成的损害,并通过公式,计算了三相电压不平衡时变压器的容量损耗以及输电线路的不平衡附加线损值。本文针对以下几种引起三相电压不平衡的不同起因,进行了研究分析：1、当电力系统的配出线路基本为架空线,且没有进行换位,导致三相对地电容不平衡时,将出现中性点位移电压,引发三相电压不平衡现象。2、中性点经消弧线圈接地的系统中,消弧线圈将放大三相电压的不平衡度。还容易与系统中的线路、母线等容性元件产生谐振,引起三相电压的剧烈波动,对电力系统危害极大。3、电力系统处于欠补偿运行时,出现开关合闸、单相接地等扰动激发导致电磁式电压互感器铁心磁饱和,从而产生铁磁谐振,引起三相电压不平衡。4、在大连地区,普遍存在三相负荷不平衡现象,特别电气化铁路的牵引机车及炼钢、电解铝等冲击性负荷大量分布各地。虽然在入网时考虑到尽量平均分配三相负荷,但其常伴有随机性与非同时性,表现为三相不平衡负荷,导致三相电压不平衡。5、电力系统在发生单相接地、线路断线以及谐振等异常时,也会发生三相电压不平衡现象。本课题以大连某个三相电压不平衡度超出国家标准的66kV系统为例,利用MATLAB软件中的simulink工具箱,根据实际的运行参数,建立仿真模型。并提出在相电压最低的线路末端加装电容器的方法来降低三相电压不平衡度。通过仿真分析,验证该方法的可能性。本文的研究方法和结果为降低大连地区三相电压不平衡度提供一种简单的方法。
[Abstract]:Three-phase voltage imbalance will occur in power system under normal operation and accident. This paper mainly analyzes the phenomenon of three-phase voltage imbalance in normal operation. Damage caused by various electrical equipment in transmission and distribution links, and through formulas, The capacity loss of transformer and the additional line loss of unbalanced transmission line are calculated when the three-phase voltage is unbalanced. When the distribution line of the power system is basically an overhead line and no transposition is carried out, the neutral displacement voltage will appear when the capacitance of the power system is unbalanced and the relative capacitance is unbalanced. In a system where the neutral point is grounded by an arc-suppression coil, the arc-suppression coil will amplify the unbalance of the three-phase voltage. It is also easy to resonate with the lines and bus lines of the system. It causes severe fluctuation of three-phase voltage, which is harmful to the power system. When the power system is in undercompensated operation, the switching and closing, single-phase earthing and other disturbance excitation lead to magnetic saturation of the core of the electromagnetic voltage transformer, which results in ferroresonance. Causes three-phase voltage imbalance. 4. In Dalian area, three-phase load imbalance is common, especially traction locomotive and steel-making of electrified railway, The impact load of electrolytic aluminum is widely distributed all over the world. Although the three-phase load is considered as evenly as possible when entering the network, it is often accompanied by randomness and non-synchronization, which is manifested as three-phase unbalanced load. Leading to unbalance of three-phase voltage. 5, when the single-phase grounding, line breakage, resonance and other anomalies occur in the power system, Three-phase voltage imbalance will also occur. Taking a 66 kV system with a three-phase voltage unbalance degree exceeding the national standard as an example, using the simulink toolbox in MATLAB software, according to the actual operation parameters, The simulation model is established, and the method of adding capacitors at the end of the line with the lowest phase voltage is put forward to reduce the imbalance of three-phase voltage. The research methods and results in this paper provide a simple method to reduce the unbalance of three-phase voltage in Dalian area.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM711

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