【作者】 杜言；

【导师】 廖瑞金；

【作者基本信息】 重庆大学 ， 电气工程， 2006， 硕士

【摘要】 随着我国电力工业的发展,交联聚乙烯绝缘电力电缆(简称XLPE电缆)以其优越的电气性能和机械物理性能得到了突飞猛进的发展。为确保输电网络的安全,对XLPE电缆的检测技术受到了国内外众多专家的注意,对XLPE电缆局部放电的在线监测及定位技术就是其中的研究热点之一。本文首先研究了局部放电信号在电缆中的传输规律,在此基础上利用PSCAD/EMTDC建立了具有集肤效应的zCable电缆模型。经过仿真研究,验证了局放信号在电缆中的传输和衰减,为电缆中局放点的时延估计算法研究打下了基础。设计了一种基于自积分回路的宽频带局部放电电流传感器,分析了其性能参数,研究传感器的响应灵敏度及频带宽度与积分电阻、线圈磁芯材料、导线的截面积、线圈匝数等参数的关系。配合实验要求,设计了前置电路,搭建了满足电缆局放在线监测要求的实验平台。根据电力系统XLPE电力电缆局部放电的具体类型,实际制作了3种具有典型代表意义的放电模型,提出了具体实验方案,采集到XLPE电缆四种缺陷下的局部放电信号。用小波变换的方法对信号进行了去噪。通过仿真和实验,去噪效果达到要求。研究了小波在电缆定位中的作用,提出了基于小波的广义相关法和二次加权法这两种可用于电缆局部放电定位的时延估计算法。通过仿真研究得到结论:基于小波的广义相关法取消了直接相关法估计时延的假设条件,不论信噪是否相关,都能在尺度2~3上较准确定位;基于小波的二次加权法不仅特别适用于低信噪比情况,而且不易受信号衰减的影响,适用于长电缆局放定位,在尺度2~3、2~4上精度较高。缺点是没有克服广义相关法要求信噪互不相关的局限性。实际测量时,由于现场噪声来源复杂,应根据具体情况,综合运用两种方法。更多还原

【Abstract】 With the development of electrical industrial, XLPE has been used widely because of its superior electrical and mechanical property. In order to ensure the safety of transmission network, detection of XLPE has been paid great attention, and the on-line monitoring and location of partial discharge occurred in XLPE become one of the issues of general interest.Based on the transmission characteristic of partial discharge in cable, a zCable model considering skin effect is established by using PSCAD/EMTDC. According to simulation results, the transmission and attenuation of partial discharge have been verified which set the foundation for delay-time estimation algorithm for PD sites location.A self-integrating network based broad band current sensor for PD is designed and performance parameter are analyzed. Moreover, the response sensitivity and frequency breadth are studied from integrating resistance, magnetic core material of coil, sectional area of wire and number of windings. Front end circuit is designed and an experimental platform is established.According to specific types of partial discharge of XLPE, 3 typical discharge models are designed. During the experiment, PD signals corresponding to four defects are collected, and noise contained in them are eliminated by wavelet theory. Simulation indicate de-noise has achieve good results.Two time-delay estimation algorithms for XLPE PD sites location, namely, wavelet based general correlation method and twice weighted method, are proposed. Wavelet based general correlation method relax the assumed condition for time-delay estimation of direct correlation method, overcome the inaccuracy of location when PD signal correlate with noise, extend the application of time-delay,and have high degree of accuracy on scale 2~3. Twice-weighted method based on wavelet is not only particularly suit for time-delay estimation under low SNR,but also suit for the PD Location in long cable on scale 2~2 and 2~3 . However, it can not overcome the limitation of non-correlation between signal and noise needed by general correlation method. According to the simulation, both of the two algorithms can suit for PD location of XLPE with high accuracy. In practice, it should use them together to count various noise.更多还原