【作者】 李信；

【导师】 李成榕；

【作者基本信息】 华北电力大学（北京） ， 高电压与绝缘技术， 2005， 博士

【摘要】 全封闭气体组合电器(GIS)局部放电在线检测技术中,需要解决的关键问题是:放电类型的判别、放电源的定位和放电量的估计。 本文工作基于GIS局部放电在线检测特高频方法,研制出的两种固定式特高频介质传感器。第一种传感器利用了CT引线箱处的半封闭结构和二次引线端的绝缘结构,仿真和试验表明,在不降低GIS密封和绝缘性能情况下,传感器耦合到信号能量的大小约为普通外置式传感器的3倍,而且也具有内置传感器抗干扰的优点。第二种传感器安装在手孔位置,人为的在天线周围填充耦合介质,利用介质吸收局部放电产生的电磁波,通过仿真计算得到了介质最佳的参数:填充介质的整体厚度为2cm,介电常数为5。 本文通过试验研究了GIS内部不同缺陷类型的局部放电特征,利用一个工频周期内的UHF检波输出进行局部放电类型的识别,从特高频信号中取出低频调制信号,将特高频传感器输出的特高频成分滤除,而仅保留信号的幅值和相位信息,大大减少了数据量,降低了监测设备的硬件采样率,使得检测工作更加简便并行之有效,而且可利用检波之后的数据对多个局部放电周期进行统计工作,得到放电的分布谱图,以利于局部放电的长期监测。 本文提出了针对不同类型放电的UHF信号,利用三次样条插值结合互相关函数提取时间差和利用小波包分解结合互相关函数提取时间差的综合算法,基本上可以将定位误差范围限定在10cm内,从而提高了GIS局部放电定位的精度。为了进一步确定放电源的部位,本文利用在腔体周围放置多个传感器,发现当传感器接收位置与放电源垂直时,耦合到的能量值为最大,利用这种方法可以确定放电源的方位。为了验证特高频定位测量装置、定位综合算法和方法的整体性能,本文作者曾经对25个变电站进行实地局部放电定位测量,共发现三处变电站内存在有局部放电现象。 本文利用时域有限差分法(FDTD)对波导结构中的局部放电和信号接收情况进行了仿真,研究了影响传感器接收信号能量的各种因素,包括放电源的位置、放电源与接收点的相对角度、GIS腔体结构和脉冲的陡度(宽度和幅值)。发现传感器输出的UHF信号能量大小与放电源的放电量并无线性关系。脉冲陡度是决定UHF信号能量大小的主要因素。当脉冲宽度一定时,UHF信号能量的平方根同实际脉冲的幅值成正比。 本文提出利用局部放电源的实际放电量最大值对GIS局部放电进行估计。设定了放电量最大值对应的脉冲宽度为2.4ns,如果在同样幅值条件下,此时的实际放电量可达到最大值,但是接收点耦合到的信号能量最小。通过试验和仿真发现UHF信号能量的平方根与实际放电量之间呈线性关系,随着实际放电量的增长而增加。更多还原

【Abstract】 There are three key technologies in the on-line detection of the partial discharges in Gas Insulated Substations (GIS), the classification of partial discharge (PD), the location of PD source and the estimate of PD quantities.In ths dissertation, one kind of portable ultra-high frequency (UHF) sensor is developed, and it consists of UHF antenna, UHF amplifier and high-pass filter, the whole measure bandwidth range is 500~5000MHz. To improve the sensibility and security of the sensor, a new filled dielectric UHF sensor is developed, and chooses the CT chamber and hand hole as the best installation point. The CT chamber is of semi-closed constructure, if the sensor installed there, the insulation and sealed ability is not invariable, furthermore, the EM noise is very low, as installation of intenal sensor. In the hand hole, the high dielectric constant medium is filled in front of antenna to enhence the EM energy coupling capability. The best parameter is that depth is 2cm, and the dielectric constant is 5.The PD detector allows extracting meaningful data from UHF signal of PD, such as the amplitude and pulse phase, that can be reduce the sample rate of measurement equipment. The data from the detector can be used to statistics during some power frequencies for monitoring the PD in GISThe difference in arrival times of UHF signals at two sensors can be measured to assist with locating faults in GIS. The test results in the laboratory indicate that the fault location precision depends on the digital rate of the oscilloscope. In on-site test, if the sample rate is low, it is could not have enough sample plots to recover the real pulse wavefronts, which is difficult to identify the arrival times at the two sensors by the first peak of UHF waveform. A new algorithm has been described, which applies cubic spline interpolation to increase points between two real sample points, and improve the location precision of time flight method.In this dissertation, author used multi-sensor to locate the PD souce’s direction in GIS, which distuibuted around the spacer vertical cross. The signal will be maximium when the sensor is vertical to the PD source.In this dissertation, GIS cavity configuration is utilized and transmission of PD electromagnetic wave in wave-guide is simulated by FDTD method. Therefore, factors influencing UHF signals are analyzed, including PD current amplitude and pulse width of PD source. The results showed that the UHF signals have no directe relation to the PD of souce. When the pulse width is constant, the square root of UHF signal energy is direct retio to the amplitude of the real pulse. Supposed that the maximium width of the pulse in GIS is 2.4ns, the original max PD quantities is composed by the maximium width and amplitude of the pulse, According to relationship between UHF signals energy and PD pulse, the original max PD quantities can be estimated, which contributes to marking GIS partial discharge.更多还原