电缆局部放电在线检测方法研究

发布时间：2018-05-25 06:04

本文选题：沟槽电缆 + 局部放电　；参考：《沈阳工业大学》2017年硕士论文

【摘要】：随着现代工业的发展和城市化水平的提高,电缆作为传输电能的重要工具,越来越得到人们的重视,其运行的可靠性直接影响电力系统的正常运行。然而电缆在运行中难免会遇到一些故障,主要是由于在电缆绝缘材料中容易产生局部放电现象,电缆绝缘材料在生产时由于加工技术的限制或者原材料有问题,导致加工完后绝缘中存在杂质或气隙,气隙和杂质尖端处是最容易发生局部放电现象的区域。电缆局部放电的大小与电缆绝缘状况的好坏息息相关,局部放电量的增加表示电缆的绝缘强度在减弱,这会危害电缆的安全运行,因此提前并准确检测局部放电的强弱是避免电缆故障最有效的方法。目前主要是定点或在离线状态下对电缆局部放电进行检测,针对传统方法检测电缆局部放电的局限性,本文对电缆局部放电超声波检测法进行深入研究。本文基于电缆绝缘层三电容模型和气隙放电力学模型解释局部放电现象以及分析局部放电产生超声波的机理,研究局部放电的分类和产生原因,同时研究局部放电超声波信号的波形特征,为电缆局部放电超声波检测法给予理论支持。针对电缆局部放电超声波信号,研究局部放电超声波信号的传播特性,分析局部放电超声波信号的频率和幅值信息,以及环境中可能存在的各种干扰信号,以此作为基础,选取适合电缆局部放电现场检测的超声波接收探头,设计信号放大、滤波等处理电路,通过计算和分析选取合适的电路参数,利用STM32单片机处理和存储模拟转换后的信号,并对电路进行了仿真和测试。利用MATLAB的GUI功能编写用户界面对数据进行处理,能够显示超声波信号波形,提取信号的包络,显示信号最大幅值及放电起始点。通过系统的实验研究,分析超声波接收探头中心频率、放电强弱以及距放电源距离对局部放电超声波信号的影响。研究结果表明局部放电能够产生类似于AM调制的超声波信号,且信号幅值与放电量成正比,与探头和放电源之间的距离成反比,在局部放电信号频率范围内,低频段局部放电信号的幅值较大,本文中探头的最优中心频率为27kHz,采用中心频率为27kHz的接收探头时,局部放电检测装置的有效检测距离为80cm,应用MATLAB提取局部放电信号的包络,能够直观地分析信号幅值及放电起始点,为判断局部放电有无、放电量大小及位置提供有效的依据。
[Abstract]:With the development of modern industry and the improvement of urbanization level, more and more attention has been paid to cable as an important tool to transmit electric energy. The reliability of cable operation directly affects the normal operation of power system. However, some faults will inevitably be encountered in the operation of the cable, mainly because partial discharge is easy to occur in the cable insulation material, and the cable insulation material is produced because of the limitation of processing technology or the problem of raw materials. After processing, there are impurities or air gaps in the insulation, and the air gap and impurity tip are the areas where partial discharge is most likely to occur. The magnitude of partial discharge of cable is closely related to the insulation condition of cable. The increase of partial discharge indicates that the insulation strength of cable is weakening, which will endanger the safe operation of cable. Therefore, early and accurate detection of partial discharge is the most effective method to avoid cable faults. At present, partial discharge of cable is mainly detected at fixed point or off-line state. Aiming at the limitation of traditional method of detecting partial discharge of cable, the ultrasonic detection method of partial discharge of cable is studied deeply in this paper. Based on the three capacitance model of insulation layer and the mechanical model of air gap discharge, this paper explains the phenomenon of partial discharge and analyzes the mechanism of partial discharge producing ultrasonic wave, and studies the classification and cause of partial discharge. At the same time, the waveform characteristics of partial discharge ultrasonic signal are studied to provide theoretical support for cable partial discharge ultrasonic detection method. According to the ultrasonic signal of partial discharge of cable, the propagation characteristic of ultrasonic signal of partial discharge is studied, and the frequency and amplitude information of ultrasonic signal of partial discharge are analyzed, as well as various kinds of interference signals that may exist in the environment. The ultrasonic receiver which is suitable for the field detection of partial discharge of cable is selected, the signal amplification and filter are designed, the suitable circuit parameters are selected by calculation and analysis, and the signal after analog conversion is processed and stored by STM32 single chip computer. The circuit is simulated and tested. Using the GUI function of MATLAB to write the user interface to process the data, the ultrasonic signal waveform can be displayed, the envelope of the signal can be extracted, the maximum value of the signal and the starting point of discharge can be displayed. The influence of the center frequency of ultrasonic receiver probe, discharge intensity and distance from the discharge source on the ultrasonic signal of partial discharge is analyzed. The results show that partial discharge can produce an ultrasonic signal similar to AM modulation, and the amplitude of the signal is proportional to the discharge quantity, and inversely proportional to the distance between the probe and the discharge source, and in the frequency range of the partial discharge signal. The amplitude of PD signal in low frequency band is large. The optimum center frequency of probe is 27kHz. When the receiver with 27kHz central frequency is adopted, the effective detection distance of PD detector is 80 cm. The envelope of PD signal is extracted by MATLAB. The signal amplitude and the starting point of the discharge can be analyzed intuitively, which provides an effective basis for judging whether the partial discharge exists, the magnitude and the position of the discharge.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM855

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