通过浇注孔检测GIS内部局部放电UHF信号

发布时间：2018-02-12 21:20

本文关键词： 气体绝缘开关设备局部放电特高频浇注孔蝶形天线　出处：《华北电力大学(北京)》2014年硕士论文　论文类型：学位论文

【摘要】：运行中的大多数气体绝缘开关设备(gas insulated switchgear, GIS)上未安装内置式特高频(ultra-high-frequency,UHF)传感器,并且盆式绝缘子被金属法兰覆盖,因此,常规的检测方法无法检测其内部局部放电的UHF信号,检测金属法兰浇注孔处辐射出来的UHF信号成为实现GIS局部放电UHF检测的唯一方法。同无金属法兰结构的裸盆子相比,金属法兰浇注孔的特殊结构和狭小尺寸会对局部放电UHF电磁波造成极大程度的衰减,而且传播出来的电磁波的特性也发生变化。因此,如果仍旧采用常规的外置式UHF传感器检测浇注孔处的局部放电信号,检测灵敏度会大幅度的降低,无法满足GIS设备故障带电检测的灵敏度要求。本课题旨在研究与开发专用于浇注孔式的局部放电UHF传感器,以提高GIS局部放电检测的灵敏度。本文研究了局部放电UHF电磁波通过浇注孔后的传播衰减特性。理论分析中,采用电磁屏蔽技术中的孔隙电磁泄露理论,得出电场方向平行于孔的短边的电磁波更容易从孔中传播出来,垂直方向的电磁波会极大程度的被衰减掉；随着入射电磁波频率的逐渐升高,浇注孔的屏蔽效能(Shielding Effectiveness, SE)逐渐下降,如45×20mm浇注孔在0.85GHz处SE为20dB,频率增大到1.71GHz后,SE几乎降为0dB；浇注孔的长边尺寸越长,可以通过信号的频段范围越宽,如通过45×20mm浇注孔的信号主要频率范围在0.85GHz以上,55×20mm时降低到0.68GHz。仿真计算中,基于时域有限差分法(FDTD)仿真了局部放电UHF信号在GIS中的传播过程,重点分析和对比了浇注孔表面和裸盆子表面的电场强度分布和频谱特性。研究表明,浇注孔处UHF信号的电场强度主分量的方向平行于孔的短边,比其他两个方向信号强约30dB,可以认为是线极化电磁波,主要能量集中在0.8～2GHz之间；裸盆子表面的信号的电场强度的方向分布相对要均匀很多,线极化程度很弱。试验验证中,在252kV GIS平台上进行了局放检测,与理论和仿真的结论取得了较好的一致性。通过分形理论、电阻加载和背腔技术研制了蝶形天线,其在0.8-2GHz上的平均等效高度达到常规天线的2.6倍；给矩形波导加脊处理,研制了双脊波导天线,平均等效高度为常规天线的1.7倍。搭建了252kV GIS局部放电UHF信号检测平台,制作了3种故障模型：高压电极、气泡放电和沿面放电故障。分析了局部放电UHF信号通过不同尺寸的浇注孔后的频带分布；试验证明了局放UHF信号浇注孔式检测的方法是可行的；测试表明,蝶形天线检测GIS局部放电浇注孔处UHF信号的灵敏度达到了15pC以下。
[Abstract]:Most gas insulated switches in operation are not equipped with built-in ultra-high-frequency ultra-high-frequency UHF sensors, and the basin insulators are covered with metal flanges. Therefore, conventional detection methods are unable to detect UHF signals from their internal partial discharges. Detecting the UHF signals radiated from the pouring holes of metal flanges is the only way to detect GIS partial discharge (GIS) UHF. The special structure and small size of metal flange pouring hole will cause great attenuation to partial discharge (UHF) electromagnetic wave, and the characteristic of electromagnetic wave will change. If the conventional external UHF sensor is still used to detect the PD signal at the gating hole, the detection sensitivity will be greatly reduced. The purpose of this paper is to study and develop a partial discharge UHF sensor for pouring holes. In order to improve the sensitivity of GIS partial discharge detection, the propagation and attenuation characteristics of partial discharge UHF electromagnetic wave passing through pouring holes are studied in this paper. In the theoretical analysis, the electromagnetic leakage theory of pore in electromagnetic shielding technology is used. It is concluded that the electromagnetic wave along the short side of the hole in the direction of the electric field is more easily propagated from the hole, and the electromagnetic wave in the vertical direction will be decayed to a great extent; as the frequency of the incident electromagnetic wave increases, The shielding efficiency of the casting hole and the shielding efficiency of the casting hole are gradually decreasing. For example, the SE of the 45 脳 20mm pouring hole is 20dB at 0.85 GHz, and the frequency increases to 1.71GHz and the SE decreases to 0dB.The longer the size of the long side of the pouring hole, the wider the frequency range of the signal. If the main frequency range of 45 脳 20mm pouring hole is reduced to 0.68 GHz when the main frequency range is above 0.85 GHz, the propagation process of partial discharge UHF signal in GIS is simulated based on finite difference time-domain (FDTD) method. The distribution of electric field intensity on the surface of the pouring hole and the surface of the bare pot are analyzed and compared. The results show that the direction of the principal component of the electric field intensity of the UHF signal at the pouring hole is parallel to the short side of the hole. Compared with the other two directional signals, it can be considered as a linear polarized electromagnetic wave with the main energy concentrated in the range of 0.82GHz. The directional distribution of the electric field intensity of the signal on the surface of the bare pot is much more uniform, and the degree of linear polarization is very weak. The PD detection on 252kV GIS platform is in good agreement with the conclusions of theory and simulation. The butterfly antenna is developed by fractal theory, resistor loading and back cavity technology. The average equivalent height of the antenna at 0.8-2GHz is 2.6 times that of the conventional antenna, the double ridge waveguide antenna is developed by ridging the rectangular waveguide, and the average equivalent height is 1.7 times that of the conventional antenna. The detection platform of 252kV GIS partial discharge (UHF) signal is built. Three fault models are made: high voltage electrode, bubble discharge and surface discharge fault. The frequency band distribution of partial discharge UHF signal through different size pouring holes is analyzed. The test results show that the method of partial discharge (UHF) signal gating hole detection is feasible, and the sensitivity of butterfly antenna to detect UHF signal at GIS partial discharge gating hole is less than 15pC.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM595

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