变压器局部放电超高频检测中的混频技术研究

APPLICATION OF FREQUENCY MIXING TECHNIQUE TO ULTRA-HIGH-FREQUENCY PD DETECTION FOR TRANSFORMERS

信号的提取和分析是局部放电超高频检测中的重点和难点,文中提出用混频技术提取局部放电信号超高频分量的新方法.用混频技术进行超高频数字信号处理的仿真实验,结果表明该技术既可保留信号包络的峰值和相位特征,又降低了超高频信号的频率.基于混频技术建立变压器局部放电超高频在线监测系统,并对典型局放模型进行实验,结果表明混频技术的应用可以有效地提取中心频率在400～800MHz之间(最小步长5MHz)、带宽为10、20、40或80MHz的局部放电超高频信号,准确地计算放电相关参数,抗干扰性强且提取的放电信息丰富,可用于变压器局部放电超高频在线监测和智能化诊断.

A new method, i.e., frequency mixing technique, was proposed to extract ultra-high-frequency (UHF) PD signals in this paper. By using this method, simulation studies were made to process UHF PD signals. Results showed that this method not only kept the peak value and phase characteristics, but also reduced the frequency of UHF PD signals. Based on frequency mixing technique, an on-line UHF PD monitoring system was developed for transformers. With this system, some typical PD models were detected. Experimental results showed that the technique can effectively detect the time and the amplitude of the high-frequency (adjustable center frequency between 400~800 MHz in minimum steps of 5MHz) and narrowband (10, 20, 40 or 80MHz) signals emitted from PD, calculate accurately phase resolved PD patterns and statistical operators, suppress effectively interference from background, and be useful for on-line monitoring and intelligent diagnosis of UHF PD in transformers.