变压器套管局部放电射频信号在外部空间的分布特征

Distribution Characteristics of Partial Discharge Radio Frequency Signal in Transformer Tank and Bushing

外置式局部放电射频检测方法适用于在运行的设备,目前已成为感知变压器与套管绝缘缺陷的重要手段之一。其检测灵敏度受到传感器安装位置与极化方向匹配的影响。为了提高外置式射频检测方法的灵敏度,研究了变压器油箱内局部放电电磁波经过套管传播至外部空间时射频信号的幅值分布特征。首先建立了套管下部局部放电电磁波的传播仿真模型;然后利用色度图展示了电磁波传播的动态过程;其次分析了套管外部典型部位的射频信号电场强度波形,以及电场强度的极化方向;最后开展了局部放电试验与射频信号测量,利用双锥天线测量结果验证了射频信号的幅值分布特征与极化特征。仿真结果表明:电磁波将以套管接地法兰、套管顶部为中心向外传播;利用双锥天线将在此2个部位附近测得较强的射频信号;当双锥天线极化方向与套管轴向平行时测得的射频信号最强。该结论对于提升变压器及套管局部放电射频检测灵敏度具有参考价值和工程意义。

The external partial discharge(PD)radio frequency(RF)detection method is suitable for equipment in operation,and has become one of the important means to perceive the insulation defects of transformer and bushing.The detection sensitivity is affected by the matching of sensor installation position and polarization direction.In order to improve the sensitivity of the external RF detection method,this paper studies the amplitude distribution characteristics of the RF signal when the partial discharge electromagnetic wave in the transformer tank propagates through the bushing to the external space.Firstly,the propagation simulation model of partial discharge electromagnetic wave under bushing is established.Secondly,the dynamic process of electromagnetic wave propagation is shown by chromaticity diagram.Thirdly,the electric field intensity waveform of RF signal and the polarization direction of electric field intensity at typical locations outside the bushing are analyzed.Finally,partial discharge test and RF signal measurement are carried out,and the amplitude distribution characteristics and polarization characteristics of RF signal are verified by the measurement results of biconical antenna.The simulation results show that the electromagnetic wave propagates outward with the bushing grounding flange and the bushing top as the center;strong RF signals are measured near the two positions using the biconical antenna;the measured RF signal is the strongest when the polarization direction of the biconical antenna is parallel to the axial direction of the bushing.This conclusion is significant for improving the sensitivity of transformer and bushing partial discharge radio frequency detection.