交联电力电缆的交接和预防性试验

阐述了交联聚乙烯绝缘电缆的交接和预防性试验的有关问题,提出6 kV~10 kV和35 kV交联聚乙烯绝缘电缆不同的试验方法和内容,并指出对交联聚乙烯绝缘电缆的交接和预防性试验应优先采用变频率串联谐振试验,以保证其安全运行。     

考虑负荷特性的XLPE电缆绝缘老化程度研究

为了规避传统介损在线监测法带来的电流传感器测量误差以及环境的影响,建立了基于泄漏电流矢量差的电缆相对绝缘老化程度的判断依据。首先,分析了基于电缆不同连接方式的电缆介损;然后,在考虑电缆所接负荷的负荷特性的基础上,分析了泄漏电流的变化特性,得出了接地电流的变化量与泄漏电流的变化量相同,可以通过接地电流值的变化特性判断电缆绝缘老化程度的结论。最后,利用仿真分析了改变电缆绝缘等效阻抗模拟电缆绝缘老化情况下,电缆泄漏电流与接地电流的变化特性,验证了理论分析的准确性与有效性。     

Understanding Electrical Performance and Microstructure of Water Tree Aged Cables after Silicone Injection during Electrical-Thermal Accelerated Aging

To further understand the long-term effect of rejuvenation fluid on water tree aged cross-linked polyethylene (XLPE) cables after silicone injection, electrical performance and microstructure of water tree aged cables were investigated during an electrical-thermal accelerated aging experiment. Two groups of treated and untreated water tree aged cable samples were subjected to electrical-thermal aging for 2 weeks. The results of the dielectric loss factor showed that the electrical performance of the treated samples was significantly better than that of untreated samples after electrical-thermal aging. Microobservation results showed that the overall water tree sizes of the treated samples were much smaller than those of the untreated samples after electrical-thermal aging. Furthermore, there was a second growth of water trees in the original water tree region during electrical-thermal aging in both groups of samples. Using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), rejuvenation fillers were observed tightly embedded in water tree voids after electrical-thermal aging. The infrared (IR) spectroscopy analysis results showed that the concentration of rejuvenation fluid increased from the outer layer to the inner layer of insulation. Based on the results, due to the improvement of the electric field at the water tree tip and the diffusion of silicone fluid in the insulation layer, both the second growth in the original water tree region and continuing growth at the water tree tip can be effectively inhibited.     

Investigation of Water Tree Degradation in Dry‐Cured and Extruded Three‐Layer (E‐E Type) 6.6‐kV Removed XLPE Cables

Dry‐cured and extruded three‐layer (E‐E type) 6.6‐kV cross‐linked polyethylene (XLPE) cables were introduced into electric power systems more than 30 years ago, but they do not experience failures because of water tree degradation. Also, the degradation index of water treeing for these cables has not been established. Therefore, investigating results of residual breakdown voltage and water tree degradation of these cables will help us plan for cable replacement and determine water tree degradation diagnosis scheduling, and will be fundamental data for cable lifetime evaluation. In this study, the authors measured the ac breakdown voltages of dry‐cured and E‐E type 6.6‐kV XLPE cables removed after 18 to 25 years of operation and observed the water trees in their XLPE insulation. As a result, it was observed that breakdown voltages were larger than the maximum operating voltage (6.9 kV) and the ac voltage for the dielectric withstanding test (10.3 kV). Water trees were mainly bow‐tie water trees and their maximum length was approximately 1 mm. Although the number of measured cables was limited, the lifetime of this type of cable was estimated to be approximately 40 years, even experiencing water immersion.     

电力电缆变频谐振耐压试验分析

随着交联聚乙烯（XLPE）电力电缆在城市电网中的大量应用,直流耐压试验方法已经不再适用于XLPE电缆。但工频交流耐压试验设备笨重,不适合现场应用,近年来理论和实践都证明变频谐振试验是替代工频试验的最佳选择。本文从理论和应用方面探讨了变频谐振试验方法。     

用于现场老化交联聚乙烯电力电缆的降解评估参数

The cables are more likely to deteriorate after several years of service in Shanghai,a city with a humid climate and abundant rainfall.Before assessing the aging status of those cables,it is critical to present effective test parameters which are sensitive to the aging process under special field conditions.Therefore,we have performed water tree investigation,tensile test,and differential scanning calorimetry(DSC)test on hundreds of cable samples removed from service.A large number of typical bowtie water trees were found in cable insulation and the water tree content was proposed to characterize the degree of water treeing.Based on Arrhenius Equation and equivalent thermal history parameters estimated from DSC profiles,we also proposed a new parameter ln(t/τθ)to characterize the aging status of cable insulation,Where,t is treated duration andτθis the thermal life under treated temperature.The applicabilities of water tree content,tensile strength,and ln(t/τθ)are tested using the analysis of variance(ANOVA).Then we investigated the relationship between the tensile strength and the water tree content using regression analysis,and analyzed the relationship between ln(t/τθ)and the tensile strength.The results indicated that each of these parameters performs differently with cables which experienced different degrees of age related degradation,and can be used to identify the aging status of field aged cables.The tensile strength can reflect the water treeing condition of field aged cables very well as a commonly used functional parameter.Since ln(t/τθ)is strongly related to the tensile strength,it is an effective parameter to characterize the aging status of field aged cable insulation.Using this newly proposed parameter is more time saving because of the convenience in sampling.     

振荡波电压下10kV交联聚乙烯电缆中间接头的局部放电特性

交联聚乙烯(XLPE)电缆局部放电的振荡波电压检测方法是一种无损检测方法,目前已得到初步应用。为了研究振荡波电压下电缆典型缺陷的局部放电特性,制作了4种10 k V交联聚乙烯电缆中间接头人工缺陷模型,对4种缺陷模型分别施加振荡波电压和工频电压,对比研究了振荡波电压和工频电压下的局部放电特性。研究结果表明:相较于工频电压,振荡波电压下局部放电的脉冲信号上升沿更陡峭,过峰值后衰减更快,在2~3个周期内衰减到0,脉冲持续时间短约3~30μs;同一种缺陷的局部放电3维统计图谱在振荡波电压与工频电压下基本一致,不同缺陷的局部放电3维统计图谱区别明显,为进一步研究振荡波电压作用下交联聚乙烯电缆局部放电的模式识别奠定了基础。     

交联聚乙烯绝缘电缆交联工艺介绍及应用

介绍了交联聚乙烯绝缘电缆的几种交联工艺,分析对比了过氧化物化学交联、硅烷交联和辐照交联的性能特点,及其在电力电缆中的应用。     

XLPE电缆绝缘老化与剩余寿命评估的试验方法

电缆投入运行后.绝缘会受到电、热、机械、水分等因素的作用而发生老化,影响电缆的运行可靠性和使用寿命.XLPE电缆的绝缘状态与剩余寿命的评估是目前的热点问题,相对于定性的分析,对电缆剩余寿命的定量评估更有实际价值.文章总结了XLPE电缆绝缘老化机理并调研了几种定量分析电缆剩余寿命的方法:击穿电压对比法,介质损耗因素法和直流泄漏电流法.可为从事电缆运行情况和寿命研究的技术人员提供参考.