【作者】 孙彤；

【导师】 高有华；

【作者基本信息】 沈阳工业大学 ， 电气工程， 2008， 硕士

【摘要】 气体绝缘金属封闭式开关装置(GIS)以其占地面积小、运行稳定和维护方便等一系列优点,越来越多地用于电力系统中。GIS中的隔离开关在分合空母线时,由于触头运动速度慢,开关本身的灭弧性能差,故触头间隙间会发生多次重燃,引起快速暂态过电压(VFTO)。这种不同于冲击电压和雷电波、具有截波特征的过电压具有上升时间短、幅值高的特点,有几纳秒到几十纳秒的波头,对GIS设备不同部位,如母线支撑件、套管以及开关本身的绝缘都有很大的危害,影响开关设备本身的可靠性,甚至危及到相连设备变压器的绝缘性能。本文首先根据GIS的实际结构特点,对各元件进行合理近似的等效,确定了GIS中集中元件电阻、电感、电容和无损传输线的等效暂态电路模型;确定了变压器、断路器的等效暂态电路模型和隔离开关燃弧和未燃弧两种情况下的暂态电路模型。并依据电感、电容的计算公式,计算出了变压器、断路器、传输线、接地开关和隔离开关的等值参数值。其次,根据实际的500kV GIS中隔离开关分合母线充电电流时产生的快速暂态过电压电路,确定了各元件的暂态电路模型,从而给出了VFTO数值模拟的等值电路模型。建立了暂态过电压计算的节点电压方程,对VFTO进行了数值模拟,计算了不同部位的暂态过电压的波形,给出了不同元件上暂态过电压的幅值及发生时间。最后,本文对快速暂态过电压(VFTO)波形进行离散傅里叶变换,确定了VFTO的频率成份及幅值特征,分析了频率产生的原因,研究了VFTO对GIS设备中元件绝缘的影响。通过计算分析,讨论了变压器入口电容、母线残余电荷以及支撑绝缘子等元件参数的变化对VFTO波形及其幅值的影响,并给出了VFTO的变化规律。指出了影响VFTO数值的关键因素是变压器的等值入口电容值。此外,选用较大的弧道电阻值、适当增加电缆长度和采用氧化锌避雷器等也对VFTO的幅值有一定的抑制作用。故随着我国超高压GIS的迅速发展,应对其中隔离开关操作所产生的特快速暂态过程高度重视,采取必要的措施限制此类过电压,以提高GIS运行的可靠性。更多还原

【Abstract】 More and more Gas Insulated Switchgear (GIS) has been put in use in electric power system for their advantage of less area occupancy, steady run and maintaining convenience. When disconnector switched on and switched off charging current circuit, Very Fast Transient Overvoltage (VFTO) is caused by slow contact sports, the interrupter switch their poor performance, the gap between contact will be renewed repeatedly occurred. VFTO has the characteristic of the steep front and high amplitude value. It has the wave head of several nanosecond to several tens nanosecond. VFTO has the characteristic of intercepting wave, and it is very dangerous to the different parts of GIS equipment, such as the insulation of bus support, casing pipe and switch self. It has the effect on the reliability of switch equipment, and endangers the insulating property of transformer which is connected to GIS.First of all, according to the actual structure of GIS, the various components of the equivalent reasonable approximation are brought up. The dynamic circuit model of focuing on components resistors, inductors, capacitors and lossless transmission line are confirmed, and the dynamic circuit model of transformer, bresker and disconnect switch which of arc and unburned arc as well. According to the formula of inductors and capacitors, parameters of components are also calculated.Secondly, in this paper, with regarding to a charged electric current circuit of practical 500kV GIS is presented, in which the disconnect switch is disconnecting and closing the bus. The dynamic circuit model of each component is confirmed, and the equivalence circuit model of VFTO is brought up. The node voltage equations of calculating the transient overvoltage are built up to calculate the transient overvoltage, and then numerically simulated VFTO. The wave shapes of transient overvoltage to different parts are calculated, and the amplitude value and the occurred time of transient overvoltage to different components are presented. VFTO poses a threat to the insulation of electric power transformer, which is connected to GIS. Finally, according to the VFTO waveform of the Discrete Fourier Transform, when the parameters of components changed, the effects on the amplitude value of VFTO are discussed. And then the characteristic of frequency and amplitude value of VFTO are analyzed so that the effects on the components insulation of GIS equipment are studied. The wave shape of VFTO along with time is also presented. Then when the parameter of transformer’s entrance capacitance and bus’s remain charge as well as support insulator are endowed with different value, the influence on the wave shape and the change rules of VFTO is discussed. In addition, selection of the larger arc of resistance values, appropriate to increase the length of cable and the use of zinc oxide surge arresters, also on the amplitude VFTO have some effect. With rapid development of the GIS UHP, we deal with the isolation switch operation by special fast transient attach great importance to the process. We will take the necessary measures to limit the overvoltage to enhance the reliability of GIS.更多还原