A Thesis Submitted in Partial Fulfillment of the Requirements
for the Degree for the Master of Engineering
The Rearch of Characteristics of Very Fast Transient Overvoltage in UHV GIS System
Candidate: Zhou Ting
Major : Electrical Engineering
Supervisor: Assoc. Prof. Xu Tao
Prof. Wen Y uanfang
Huazhong University of Science & Technology
Wuhan 430074, P.R.China
January, 9th, 2013
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摘要
随着电力系统超特高压线路的不断投入运行，相应的电力系统出现的过电压也在不断提高，为了维护电力系统运行的稳定与可靠性，对超特高压系统的绝缘设计提出了更高的要求。本文的研究对象是GIS隔离开关操作时产生的特快速暂态过电压（VFTO），它的幅值与随着系统电压等级的提高而成比例提高。在电压等级较低时，VFTO并非GIS绝缘设计时需要考虑的因素，而当电压等级增加时，相应的绝缘设计并没有成比例增加，所以在电压等级较高的系统中，VFTO造成的事故时有发生。文章主要针对武汉凤凰山特高压交流试验基地的1100kV电压等级的GIS 开合隔离开关时产生的快速暂态过电压进行现场实测和仿真研究。
在现场试验中，采用方便实用可靠性高的锥形电容分压传感器，在GIS的负载侧和电源侧一共设置了5个不同测点，负载侧用直流电源对其进行充电等效实际系统运行时的残压。由于电源合闸相位的不确定性，进行了数百组的试验以得到最大的VFTO值。试验结果显示在分闸的后段以及合闸的前段会出
现幅值较大的过电压，在GIS的短线末端处会有较高幅值的VFTO，而越远离操作刀，其过电压幅值有下降趋势。
数值仿真计算中，本文首先将试验系统中的各个元件等效成暂态模型，运用EMTP/ATP暂态仿真软件对试验系统进行建模，输入正确的参数，通过改变GIS短管母线的长度以及并联分合闸电阻的阻值来说明GIS中产生VFTO的特性。仿真结果显示，GIS中产生的VFTO与试验中有相同的分布特性，即在GIS的短管末端由于行波的全反射作用会有较高的幅值；GIS侧管母线末端产生的VFTO幅值随着它自身长度的减小而增大，并且相应的频率分量也有增大的趋势；并联分合闸电阻对快速暂态过电压有很好的抑制作用，在并联电阻阻值较小时，抑制作用明显，当并联电阻阻值继续增大时，VFTO的减小不明显，在并联电阻为500Ω时就系统产生的最大过电压远小于GIS本身的过电压耐受能力，因此综合经济和安全性两方面的考虑在实际GIS系统中推荐使用500Ω电阻。
关键词：特高压系统GIS 快速暂态过电压（VFTO）分合闸电阻
Abstract
With the continuous improvement of the voltage level of the power system, power system overvoltage is also rising, the UHV system insulation design put forward higher requirements in order to maintain the stability and reliability of the power system operation. The object of this paper i
s the V ery V ast Transient Overvoltage (VFTO) which caud by the operation of disconnecting switch in GIS, its amplitude has a proportional relationship with the voltage level of the power system, at a lower voltage level, VFTO in GIS is not a factor need to be considered in insulated design, but when the voltage level is incread, the corresponding insulation design doesn’t increa proportionally, accidents caud by VFTO have occurred in systems with a higher voltage level. This paper focud on the very fast transient overvoltage caud by 1100kV voltage level GIS in Wuhan Phoenix Mountain UHV AC test ba with Field measurements and simulation studies.
In field tests, using a convenient , practical and high reliability tapered capacitive partial voltage nsor, with a total t of 5 different points in the load side and the power supply side of the GIS, and the DC power supply in load-side charging the GIS is equal with the residual pressure in actual power system. In order to get the maximum VFTO hundreds of tests have been taken due to the uncertainly pha of switch operation. The test results show the overvoltage amplitude of closing the gate slightly larger than that of opening; there will be a higher amplitude VFTO at the end of the GIS; the overvoltage amplitude has a downward trend in the points much more away from the operating knife.
In simulation numerical calculation, first of all, we get the transient model of various components of t
he test system, using EMTP/A TP transient simulation software to model test system, enter the correct parameters, by changing the length of the GIS short tube bus and the parallel resistor to e the characteristics of VFTO. The simulation results show that the GIS generated VFTO trial the same gment characteristics, and that there will be a higher amplitude in the short end of the tube in GIS due to the total reflection of traveling wave; the GIS side tube bus terminus generated VFTO amplitude value which increas while decreasing its own length, and also has a tendency to increa the corresponding frequency component; taking brake resistors will have good inhibition of
VFTO, but inhibition decreas with the increa of the parallel resistance, recommended closing resistors of 500Ω resistance.
Keywords:UHV System GIS V ery Fast Transient Overvoltage(VFTO) Opening and Closing Resistor
