基金项目:
国家自然科学基金(51377175);
云南电力公司科技项目(K-YN2014-031);
Project supported by National Natural Science Foundation of China (51377175), Science and Technology Fund of Yunnan Power Grid Corporation (K-YN2014-031);
When impulse frequency response analysis is applied to online detect transformer winding deformation, the time domain characteristic of transient signal can not be depicted by conventional frequency response curves, and the limitations of fast Fourier transform (FFT) can result in deletion of available information. To overcome above problem, continuous wavelet transform was used to process transient signal, in which transient signal was obtained through online impulse signal injection, the wavelet time-frequency spectrum was plotted and matrix similarity was chosen as an indicator to diagnose fault. Firstly, a simulation model of single winding was constructed after theoretical deduction, the simulation analysis of different fault types was performed. Secondly, the faulty winding test was conducted, the time-frequency characteristic of detection signal was analyzed. In addition, the matrix similarity was used to quantize the relevance of detection signal between healthy winding and fault winding. Results show that the wavelet time-frequency spectrum under different fault types is significantly different from that of healthy winding, in which the deviations of spectrum in different frequency bands present similar regularity with the frequency response. Compared with healthy transformer, wavelet time-frequency spectrum of tested faulty winding shows significant difference beyond 0.6 MHz, which shows rightful characteristic of winding capacitive fault. In 0~0.6 MHz, matrix similarity of tested winding is 0.928 0, larger than the correlation coefficient 0.800 3 between signatures obtained by FFT, which shows priority of wavelet transform. Both the simulation analysis and experimental studies show the feasibility of the proposed method.
KEY WORDS :transformer;winding deformation;impulse frequency response;continuous wavelet transform;wavelet time-frequency spectrum;matrix similarity;
国内外学者开展了多种方法进行绕组变形故障的检测[2],主要包括振动分析法[3]、超声波法[4]、发散系数法等非电测法,以及短路阻抗法[5]和频率响应法[6]等电测法。其中,频率响应法由于具有稳定性好、有效、无损、经济、简单等特点,广泛应用于变压器检测项目中。频率响应法分为正弦频率响应法(sweep frequency response analysis, SFRA)和脉冲频率响应法(impulse frequency response analysis, IFRA)[7]。国内应用较多的是正弦频率响应法,该方法也先后颁布了中国电力行业标准和IEC标准[8-9]。而对于脉冲频率响应法,国外研究报道较多,英属哥伦比亚大学的Tom De Rybel研究从套管末屏向绕组注入高频脉冲信号,制作了实验室样机[10];哥伦比亚的Eduardo Gómez-Luna研究用小波变换从暂态信号获取绕组的频率响应,开展了仿真与试验验证[11-12];加拿大PowerTech Labs公司的May Wang提出利用电力系统暂态过电压信号开展变压器绕组变形在线监测,并进行了大量试验[13]。不管是利用电力系统暂态信号,还是向绕组注入脉冲信号,与正弦频率响应法相比,脉冲频率响应法的暂态信号持续时间较短且能量较小,几乎不对变压器的运行造成影响;另外该方法所用设备简单,成本较低,现场应用可快速获得信噪比较高的检测信号,具备实现在线检测变压器绕组变形的潜力。
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