近年来气体绝缘组合电器（GIS）的绝缘故障给电力系统安全运行带来了严重危害。为了监测GIS绝缘状态，广泛采用特高频局部放电检测法。特高频检测包括局部放电特高频信号耦合和信号处理。特高频信号耦合受三因素影响，分别是放电源频谱特征，GIS中特高频信号的激发和传播特征以及传感器的设置和性能。本文首先研究GIS中典型缺陷局部放电的时域幅值和频谱分布特征。试验中设计并制作了四种典型放电源，同时改变放电模型的结构尺寸，研究结构尺寸对放电源频谱特征的影响，并探讨每种缺陷放电特征的一致性。通过大量试验，揭示了局部放电源的本质特征。接着文中分析了GIS中特高频信号的激发机理，推导出径向TEM模电场，和高次模（TE和TM）电场的表达式，然后利用XFDTD仿真分析GIS中径向电场的激发过程。根据TEM波和高次模波的不同特征，将电磁波中的TEM分量和高次模分量近似分离，发现GIS中局部放电信号以高次模分量为主。通过仿真和试验发现，当放电源远离内导体时，低频分量（800MHz以下）会减小，而高频分量（1GHz以上）将增大，而且高次模所占比升高。GIS的结构尺寸将影响局部放电信号，文中改变内导体的尺寸，发现局部放电信号的频谱特征发生了显著变化。文中利用HFSS仿真分析局部放电信号经过典型GIS结构的模态转化和传输效率，发现经过L型结构和T型结构，在拐弯方向TEM波和高次模波之间将相互转化。同时利用仿真和试验分析四种缺陷的放电信号经过四种GIS结构的频谱变化和衰减特性。发现低频TEM模分量主要由于GIS结构引起的反射造成信号幅值和能量衰减，而高次模分量则由于色散现象和模态转化的影响，造成信号幅值衰减，波形畸变。为了利用特高频信号评估GIS内部局部放电的严重程度，文中用特高频检测法和IEC60270法同时检测三种典型局部放电。分析放电量与局部放电特高频信号时域幅值和信号功率之间的联系。通过试验分析发现利用信号功率可准确评估GIS中局部放电的严重程度。最后本文提出了三个改进CIGRE特高频检测灵敏度校验方案的措施，制定了特高频测量系统灵敏度和线性度的检验策略。

The ultra high frequency (UHF) method for PD detection is widly applied to monitor the condition of the insulation in GIS. The coupling of UHF signal and the processing of the signal constitute the UHF detection method. There are three key components for the coupling of UHF signal, including the frequency spectrum characteristics of PD source, the propagation characteristics in GIS, the coupling style and the capability of the UHF coupler. Firstly, this paper focused on the intrinsic characteristics of the typical defect in GIS, such as the amplitude of the time-domain signal and the frequency spectrum characteristics. Four types of typical PD sources were designed and fabricated. Several different structure sizes of the defect were applied to make sure the consistency of the results and discover the factors that affect the frequency spectrum characteristics. The results of the study presented the essential characteristics of the partial discharge. Secondly, the fundamental theory describing the excitation of ultra high frequency signal by PD pulse in GIS was analyzed, and the radial electric field in the GIS excited by the PD pulse was expressed by the appropriate Green’s dyadic, including the TEM mode and the high order mode, such as TE11, TE21 and TM01 etc. The Finite Difference-Time Domain (FDTD) method was applied to analyze the proportions of the TEM mode and high order mode, and the influence of position of the PD source. According to the unique characteristics of TEM wave and high order mode wave, they were separated approximately. Firstly, it was discovered that the high order mode was the main component of the electric field around the enclosure in GIS. Besides that, when the distance between PD source and inner conductor increased gradually, the low frequency component decreased correspondingly, but the frequency component beyond 1 GHZ got larger contrarily, and the proportion of high order mode also increased. The structure size of GIS had great impacts on the PD signal, because the cutoff frequency of high order mode of electromagnetic (EM) wave depends on the diameters of the inner conductor and the enclosure. In this paper by varying center conductor size, it was confirmed that frequency spectrum of PD was influenced by the the inner conductor diameter.High Frequency Structure Simulator (HFSS) was adopted to simulate propagation process of the different model EM-wave though typical GIS structure. It was found that through the L-shaped and the T-shaped structures, the TEM mode and the high order mode component of PD signal transformed to each other in the turning direction. The FDTD method and experiment were also used to analyze frequency spectrum variations and propagation attenuation properties of the typical PD sources through the spacer, L-shaped branch and T branch. It was found that the attenuation of the low frequency component of PD signal was mainly resulted by the reflection of the GIS structure, meanwhile the dispersion and mode transfoemation of high order mode caused the loss of high frequency beyond 300 MHz component in GIS.In order to assess the severity of PD defects using UHF method, the partial discharge was simultaneously measured using UHF method and the IEC60270 measurement technique. The relationship between the apparent charge and the amplitude of the time domain signal, the integral energy of signal induced by PD in GIS were analyzed carefully. Power was proposed to be used for the evaluation of severity of partial discharge in GIS. Eventually, several proposals were presented to improve The GIGRE method for the sensitivity verification of UHF PD detection system, and the strategy was developed to verify the highest sensitivity and linearity of UHF PD detection system.