In order to solve the problems of TEV(transient earth voltage) utilization,such as single judgment criterion and low reliability of PD detection in HV switchboard,this paper discussed the method on how to make a bette...In order to solve the problems of TEV(transient earth voltage) utilization,such as single judgment criterion and low reliability of PD detection in HV switchboard,this paper discussed the method on how to make a better utilization of TEV in PD detection of metal-enclosed switchgears.Through discussing the relationship among the temporal phase,number of pulses and threshold of measuring and extracting the features corresponding to different typical defects,test results showed that the needle discharge distributed in 0°～90°and 200°～340°with low appearance probability above high measurement threshold;internal discharge distributed in 0°～90°and 270°～315°,and showed a similar decreasing trend under increasing of the threshold in the two regions;suspended discharge distributed in 0°～135°and 180°～315°where the PD in negative half periods decreased more seriously than those in positive half with increasing threshold.These results followed the doctrine of consistency with the conclusions that were obtained by using the traditional pulse current method.The possibility of using TEV method to make identification of PD defects has been proved to prepare for further research.展开更多
针对高密度聚乙烯(High Density Polyethylene,HDPE)管热熔接头相控阵超声检测时存在的图谱判读效率低、人员经验要求高等问题,文章提出一种基于改进YoloX算法的热熔接头全聚焦(Total Focusing Method,TFM)相控阵超声图谱缺陷(以孔洞为...针对高密度聚乙烯(High Density Polyethylene,HDPE)管热熔接头相控阵超声检测时存在的图谱判读效率低、人员经验要求高等问题,文章提出一种基于改进YoloX算法的热熔接头全聚焦(Total Focusing Method,TFM)相控阵超声图谱缺陷(以孔洞为例)智能识别方法。在YoloX的加强特征提取网络中引入卷积注意力机制模块,提高模型对缺陷信息的关注度,使用CIoU损失函数计算回归损失,以提升模型的定位精度,降低漏检率。通过TFM相控阵超声检测实验,采集原始缺陷图谱,并在完成图像增强后创建数据集。采用迁移学习策略进行训练,加快模型收敛速度。结果表明:该方法对缺陷的识别精度达98.18%,检测平均速度达23.92帧·s^(-1),检测精度相较于原YoloX模型提升了2.57个百分点且对小目标缺陷有更好的检测效果。文中方法可以识别出TFM相控阵超声图谱中的缺陷,为热熔接头的精确检测提供技术支撑。展开更多
为了研究水树老化电缆极化-去极化电流(polarization and depolarization current,PDC)支路参数变化特征及原因,分析了水树微观结构特征,并揭示了水树微观结构对电缆PDC支路参数的影响。对短电缆和长电缆样本进行加速水树老化,利用PDC...为了研究水树老化电缆极化-去极化电流(polarization and depolarization current,PDC)支路参数变化特征及原因,分析了水树微观结构特征,并揭示了水树微观结构对电缆PDC支路参数的影响。对短电缆和长电缆样本进行加速水树老化,利用PDC检测样本极化–去极化电流,并计算老化样本Debye模型三支路参数。利用光学显微镜观测短电缆样本中的水树形态,利用扫描电镜(scanning electron microscopy,SEM)观测水树区域微观形貌。PDC三支路参数辨识结果表明,水树老化样本第3支路时间常数显著高于未老化样本。另外,第3支路电容增加量高于电阻减小量。微观观测结果表明水树区域存在大量孤立微孔,分析认为,水树生长将造成材料分子链断裂及形成大量微孔–XLPE界面,导致材料偶极极化时间及界面极化时间增长,样本第3支路时间常数显著增大。另外,水树区域存在大量孤立微孔,其限制了离子在水树区域的运动,从而导致样本第3支路电容增大量高于电阻减小量。展开更多
基金Supported by National Natural Science Foundation of China(50907051)
文摘In order to solve the problems of TEV(transient earth voltage) utilization,such as single judgment criterion and low reliability of PD detection in HV switchboard,this paper discussed the method on how to make a better utilization of TEV in PD detection of metal-enclosed switchgears.Through discussing the relationship among the temporal phase,number of pulses and threshold of measuring and extracting the features corresponding to different typical defects,test results showed that the needle discharge distributed in 0°～90°and 200°～340°with low appearance probability above high measurement threshold;internal discharge distributed in 0°～90°and 270°～315°,and showed a similar decreasing trend under increasing of the threshold in the two regions;suspended discharge distributed in 0°～135°and 180°～315°where the PD in negative half periods decreased more seriously than those in positive half with increasing threshold.These results followed the doctrine of consistency with the conclusions that were obtained by using the traditional pulse current method.The possibility of using TEV method to make identification of PD defects has been proved to prepare for further research.
文摘针对高密度聚乙烯(High Density Polyethylene,HDPE)管热熔接头相控阵超声检测时存在的图谱判读效率低、人员经验要求高等问题,文章提出一种基于改进YoloX算法的热熔接头全聚焦(Total Focusing Method,TFM)相控阵超声图谱缺陷(以孔洞为例)智能识别方法。在YoloX的加强特征提取网络中引入卷积注意力机制模块,提高模型对缺陷信息的关注度,使用CIoU损失函数计算回归损失,以提升模型的定位精度,降低漏检率。通过TFM相控阵超声检测实验,采集原始缺陷图谱,并在完成图像增强后创建数据集。采用迁移学习策略进行训练,加快模型收敛速度。结果表明:该方法对缺陷的识别精度达98.18%,检测平均速度达23.92帧·s^(-1),检测精度相较于原YoloX模型提升了2.57个百分点且对小目标缺陷有更好的检测效果。文中方法可以识别出TFM相控阵超声图谱中的缺陷,为热熔接头的精确检测提供技术支撑。
文摘为了研究水树老化电缆极化-去极化电流(polarization and depolarization current,PDC)支路参数变化特征及原因,分析了水树微观结构特征,并揭示了水树微观结构对电缆PDC支路参数的影响。对短电缆和长电缆样本进行加速水树老化,利用PDC检测样本极化–去极化电流,并计算老化样本Debye模型三支路参数。利用光学显微镜观测短电缆样本中的水树形态,利用扫描电镜(scanning electron microscopy,SEM)观测水树区域微观形貌。PDC三支路参数辨识结果表明,水树老化样本第3支路时间常数显著高于未老化样本。另外,第3支路电容增加量高于电阻减小量。微观观测结果表明水树区域存在大量孤立微孔,分析认为,水树生长将造成材料分子链断裂及形成大量微孔–XLPE界面,导致材料偶极极化时间及界面极化时间增长,样本第3支路时间常数显著增大。另外,水树区域存在大量孤立微孔,其限制了离子在水树区域的运动,从而导致样本第3支路电容增大量高于电阻减小量。
