变压器局部放电源的半定松弛逐次逼近定位方法研究

发布时间：2018-02-25 04:06

本文关键词： 到达时间差定位技术半定规划理论半定松弛方法秩-1松弛逐次逼近方法　出处：《重庆大学》2014年博士论文　论文类型：学位论文

【摘要】：局部放电（Partial Discharge, PD）是电气设备内部发生绝缘缺陷时在局部范围内产生的一种放电现象。电力变压器的多数故障是由内部绝缘缺陷产生的PD，在运行电压下的不断加剧和发展，最终造成设备整体绝缘性能丧失而引发故障。这类似于“肿瘤”的发展过程与最终危害一样，PD在本领域有“绝缘肿瘤”之称。所谓“绝缘肿瘤”，具体地讲就是由于设备内部初期绝缘缺陷产生PD，可能导致局部高能电磁脉冲对装备内部绝缘材料的加速损伤，若不及早发现并加以“治理”，它会由弱变强、由局部到整体，最终可能导致绝缘材料完全丧失绝缘能力，致使装备发生绝缘击穿性损坏，进而引发电网停电事故。因此，对电力变压器内部产生的PD源进行快速、准确定位监测，不仅是保证设备安全运行的有效方法之一，也是根据绝缘故障部位对设备安全运行带来的危险程度来制定有针对性的检修策略的重要依据之一。特高频（Ultra High Frequency, UHF）检测技术具有灵敏度高、抗干扰能力强等优点，将其应用于电力变压器内部PD源的定位，一直是本领域关注的热点问题之一。但如何根据UHF PD实现准确、可靠的故障定位是电力设备状态监测急需解决的一个难题。其主要原因为电力变压器体积庞大、结构复杂、电磁环境恶劣，且其绝缘结构中缺陷类型、位置和数量具有多样性所致。此外，在PD源定位计算的过程中，除了背景噪声、传感器的响应时间、PD电流脉冲的上升时间等众多影响因素导致难以准确获取PD信号时延之外，以电磁波传播速度为等值波速建立的时间差方程组也在一定程度上影响了定位的准确性，从而出现所谓“误差多级放大”的情况，进一步降低了PD定位精度，甚至无法定位。同时，目前的定位算法还面临着对时延误差敏感、易局部收敛或发散、运算速度慢等难点。以上的不足，在一定程度上严重制约了基于UHF技术进行变压器PD源定位的应用。为此，针对到达时间差（Time Difference of Arrival, TDOA）定位法中对时延精确获取依赖性较大和因时延获取精度不高而带来定位误差较大的难题，引入“先粗后细”的理念，提出逐次逼近定位PD源的方法，以期解决针对变压器PD难以准确、快速定位的难题。本文开展的主要工作和所取得的创新性成果如下： ①提出一种基于“相关—移位—叠加”方法的四阶累积量时延估计改进算法。对来自同一放电源的多个样本数据先进行“相关-移位-叠加”数学变换后得到具有统计意义的PD信号波形，再利用四阶累积量准确地求取时间差。该方法不仅能有效消除所获PD信号的水平晃动和随机干扰，还可以有效地抑制高斯噪声提高信噪比，提高了时延测量准确性。 ②针对目前TDOA定位PD源存在对时延误差敏感、易局部收敛或发散以及运算速度慢等难点问题，提出一种可用于时间差定位方程组求解的半定松弛方法。将难以求解的时间差定位方程组通过等价变换和秩1松弛转化为一个半定规划问题，使得松弛后的问题易于求解且具有唯一的全局最优解。研究结果表明，半定松弛解法可降低对时延误差的敏感性，有效地对TDOA定位方程组进行求解，并确保得到的结果是全局最优解从而获得更高的定位精度，且较传统定位算法具有较高的定位效率。 ③为了降低时间差定位法中对准确获取时延的依赖性，提出了一种基于多样本寻优PD源的逐次逼近定位方法，以消除定位误差过大带来的PD源难以准确判断的问题。实测结果表明，提出的逐次逼近定位方法可有效地解决因时间差测量不准确而引起的定位结果较差的难题，，误差满足变压器PD定位要在数米范围内达到数厘米的定位精度要求。 ④通过采用半定松弛算法与逐次逼近定位技术对多样本数据计算后，得到的定位精度有了明显的提高，解决了单样本因时间差测量不准确而引起的定位结果分散、误差较大的问题，误差由之前单样本的数十厘米减少到数厘米，且高于用平均值法计算的结果，确保了PD源定位的准确性。且定位精度会随着每次选择样本数（即m值）的减小而变得越高，不足之处在于计算量也随之增大。
[Abstract]:Partial discharge ( PD ) is a kind of discharge phenomenon generated in the local area when the insulation defect occurs in the electrical equipment . The majority of the faults of the power transformer are the PD produced by the internal insulation defects , which can lead to the failure of the whole insulation property of the equipment . In addition , in the process of PD source positioning calculation , besides background noise , response time of sensor and rise time of PD current pulse , it is difficult to accurately obtain PD signal time delay . In addition , besides background noise , response time of sensor and rise time of PD current pulse , it is difficult to accurately obtain PD signal delay . In order to solve the difficult problem of accurate and fast positioning of transformer PD , this paper puts forward a method of successive approximation to locate the PD source in order to solve the difficult problem that the transformer PD is difficult to accurately and quickly locate . The main work and the achievements made in this paper are as follows : This paper proposes an improved algorithm based on " correlation - shift - superposition " method to estimate the fourth - order cumulant delay estimation . After the " correlation - shift - superposition " mathematical transformation is performed on multiple sample data from the same discharge source , the PD signal waveform with statistical significance is obtained , and the fourth - order cumulant is used to accurately calculate the time difference . The method not only can effectively eliminate the horizontal shaking and random interference of the obtained PD signal , but also effectively suppress the Gaussian noise and improve the signal - to - noise ratio , and improve the accuracy of time delay measurement . The results show that the semi - definite relaxation method can reduce the sensitivity of the time delay difference and solve the problem easily and have the only global optimal solution . The results show that the semi - definite relaxation method can reduce the sensitivity of the time delay difference , effectively solve the problem of the time delay difference , and ensure that the obtained result is global optimal solution so as to obtain higher positioning accuracy , and the traditional positioning algorithm has higher positioning efficiency . ( 3 ) In order to reduce the dependence of the time delay on the accurate acquisition time delay , a successive approximation positioning method based on a plurality of optimal PD sources is proposed to eliminate the problem that the PD source is difficult to judge accurately due to the excessive positioning error . The experimental results show that the proposed successive approximation positioning method can effectively solve the problem that the positioning result caused by inaccurate time difference measurement is poor , and the error satisfies the positioning accuracy requirement of the transformer PD to reach several centimeters in the range of several meters . ( 4 ) The accuracy of the positioning accuracy of PD source is solved by using semi - fixed relaxation algorithm and successive approximation positioning technique . The error is reduced from tens of centimeters of the previous single sample to several centimeters , which is higher than the result calculated by means of average method , which ensures the accuracy of PD source positioning .

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM855

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