【作者】 李道武；

【导师】 孙才新；

【作者基本信息】 重庆大学 ， 电气工程， 2004， 硕士

【摘要】 电力变压器局部放电在线监测是当前高电压绝缘检测与诊断领域研究的热点课题。由于变压器内部实际产生的局部放电信号非常微弱，加之现场严重的电磁干扰，局部放电信号的在线获取困难很大。现有技术虽然取得了一定的效果，但仍不能满足工程应用的要求。 本文针对现存的问题，从局部放电的定量测量和干扰的抑制两方面研究了脉冲电流发用于变压器局部放电在线监测。 首先，对用于变压器局部放电在线监测的谐振式空心罗戈夫斯基线圈电流传感器进行了系统的理论和仿真研究。建立了传感器的等效电路模型，经理论分析得到了传感器的传输函数；以Saber为工具，就传感器各参数对传感器的频率特性及灵敏度的影响加以研究；结合现场应用的实际，对工频大电流及雷电流下电流传感器的安全可靠性进行了核算。 首次提出了基于用谐振式空心罗戈夫斯基线圈电流传感器从高压套管取信号方式下的一种在线定量测量变压器局部放电的方法——定向耦合测量方法。通过对变电站整个运行网络阻抗特性的分析，建立了在线定量测量变压器局部放电的等效电路模型。 抑制及识别干扰是获取有效的局部放电信号的基本保证。本文在对局部放电信号和白噪的小波分解特性进行分析的基础上，从尽可能减小去噪对局部放电脉冲畸变的角度出发，分析了已广泛采用的门限值去噪算法；研究了最佳小波的选择方法。研究结果表明，采用与尺度有关的门限值处理技术不仅提高了信噪比，而且减小了对波形的畸变，较好地保持了放电脉冲的波形特征。更多还原

【Abstract】 On-line PD monitoring of power transformer is Presently the research hotspot in the area of high voltage insulation measurement and diagnosis. Due to the weakness of PD signals and bigness of interferences, the extraction of Pd pulses faces many difficulties. The developed techniques, with some achievement, have not met the demand of engineering application yet.Aiming at the present problems, this thesis studies the PD signal extraction of Pulse Current Method (PCM) in two directions: quantitative measurement and interference suppression.Firstly, theoretic and simulation research work is carried out on resonant nonmagnetic core Rogowski coil current sensor, which is usually used in PD monitoring of transformer. The equivalent circuit of sensor was designed and its transfer function was obtained through theoretically analysis. Using software Saber, the effects of coil number, parallel connection capacitance and loading resistance on the frequency responses of PD signals and the sensitivity was studied; Taking the locale application into account, the safety and reliability of the current sensor under the large power current and lightning pulse current was ensured.The directional coupling measurement, which employed resonant nonmagnetic core current sensor to induce signal from HV bushing, was first presented. The impendence characteristics of substation network are analyzed to build the equivalent circuit, which is used in PD quantitative measurement of transformers.Interference rejection and recognition is necessary to acquire the real PD pulse. Based on the analysis of wavelet decomposition characteristics of PD signals and white noise, the wavelet shrinkage denoising is analyzed in order to decrease the distortion of PD pulse caused by noise removal. Optimal wavelet selection for PD feature extraction is studied. As can be seen from the studied results, the PD S/N ratio is increased and the distortion of PD pulse caused by noise removal is decreased with the level-dependent thresholding. The method is effective for the extraction of PD signals.更多还原