振荡电压下电缆典型缺陷局部放电的统计特征及定位研究

Statistical Characteristic and Location of Partial Discharge Caused by Typical Defects in Power Cable Under Damped Oscillation Voltage

振荡波检测技术在近似于工频的阻尼振荡电压作用下检测电缆绝缘缺陷处的局部放电,具有检测结果可标定、对电缆绝缘无损伤、特别适合现场测试等优点。为研究阻尼振荡电压作用下电缆缺陷局部放电的统计特征,文中在10 kV电缆上预设了中间接头导体接管处错缠绝缘胶带、端部针尖、本体外半导电层破损、端部悬浮共计4类典型缺陷,采用自主研发的振荡波测试系统试验测量了预设缺陷的局部放电信号,应用振荡电压相位分析方法,分析了4类典型缺陷局部放电在不同严重程度时的相位统计特征。分析结果表明：4类预设缺陷的定位误差不大于10 cm;中间接头导体接管外错用绝缘胶带产生的局部放电信号呈三角形稀疏分布在振荡电压的20°~70°、200°~280°2个相位区间;端部针尖缺陷产生的局部放电信号呈矩形密集分布在振荡电压的20°~110°、200°~280°2个相位区间;外半导电层破损缺陷产生的局部放电信号呈三角形集中分布在振荡电压的180°~280°相位区间;端部悬浮缺陷产生的局部放电信号呈矩形集中分布在振荡电压的200°~300°相位区间。预设缺陷局部放电的相位谱图存在明显的特征差异,为进一步研究阻尼振荡电压作用下电缆局部放电的模式识别和放电严重程度奠定了基础。

Oscillating wave test system（OWTS） possesses such advantages as calibratable detection results,not causing deterioration in power cable insulation,especially suitable to field testing and so on while it is utilized to detect partial discharge（PD） occurred at the position of power cable,where defects exist,under damped oscillation voltage.To research statistical characteristic of PD caused by power cable defects under damped oscillation voltage,four circumstances are preset to simulate four typical cable defects,they are： A） incorrect winding-up of insulation adhesive tape at intermediate joint core,B） a nadel at the surface of conductor core pricking into insulation layer of cable,C） breakage of outer semiconducting layer of cable body and D） a extrinsic metal pin pricking into main insulation layer of cable but not touching with both surfaces of conductor core and inner semiconducting layer.Using self-developed OWTS,the PD signals caused by preset circumstances are measured,and then the phasic statisticalcircumstances are measured,and then the phasic statistical characteristics of PD caused by the four circumstances with different severities are analyzed by the phase analysis of oscillation voltage.Analysis results show that all location errors of the four preset circumstances do not exceed 10cm.The PD signals caused by circumstance A concentrate within two phase intervals of oscillation voltage from 20° to 70° and from 200° to 280° respectively and the densest distribution appears nearby 230°,and in grey image they sparsely distribute in triangle shape,and the discharge density in the negative half-cycle is slightly denser than in positive half-cycle;the PD signals caused by circumstance B concentrate within two phase intervals of oscillation voltage from 20° to 110° and from 200° to 280° respectively and in grey image they symmetrically distribute in rectangular shape,and the distribution densities in positive and negative half-cycle are basically consistent;the PD signals caused by circumstance C mainly distribute at the zero-crossing point and at the rising stage of oscillation voltage in the reverse direction,and concentrate within the phase area of oscillation voltage from 180° to 280° and in the phase interval from 190° to 230° they distribute more denser,and in grey image their distribution area presents in triangle shape;the PD signals caused by circumstance D mainly distribute in the phase area of oscillation voltage from 200° to 300°.In the phase spectrum of PD caused by preset defects there are obvious differences in statistical characteristic.Results of this research lay a foundation for further research on pattern recognition of PD in cables under damped oscillation voltage and the research on severity of PD.