基于传感器阈值法的局部放电信号自消噪

Method for PD Signal Self-denoising Based on Sensor Threshold

为抑制噪声干扰准确提取局放信号,针对局部放电脉冲的时域特征,运用电流、电容耦合以及电磁波传感器同时获取局部放电信号,将不同传感器采集的信号在时域上相乘,从而确定放电脉冲的起始和终止时间,再利用这两个阈值构建出一个时域屏蔽滤波器;运用该滤波器对含有背景噪声的原局部放电信号自行消噪,进而从噪声中提取出放电信号,提高信噪比。采用实际局部放电脉冲信号加人工模拟噪声信号对该消噪方法定量验证的结果表明,该屏蔽滤波器结构简单,容易实现在线处理,具有良好的消噪效果和应用前景。

A de-noised method based on PD signals from electrical sensors is introduced. Three kinds of sensors including current, capacitive and electromagnetic sensors are employed to obtain PD signals for the time domain characteristics of partial discharge pulses. The surface discharge model is used in the experiment. Then the signals from the three different sensors are multiplied in the time domain. It is believed that the amplitude of discharge is in- creased while the amplitude of the white noise is decreased. Therefore, the starting time and ending time of discharge can be confirmed as thresholds. Two thresholds are determined by the value of 10 percent of the discharge amplitude. A shielding filter could be constructed through the two thresholds： the value between the starting time and the ending time is set as one and the other value as zero, which means that the signals between the two thresh- olds can totally go through the filter and the signals out of them are eliminated. Then the oi-iginal PD signals with white noise are processed and denoised by the shielding filter, which improves the signal-to-noise ratio. With this shielding filter, the white noise can be totally eliminated and the discharge amplitude is not changed. The PD pulses plus the artificial white noise signals are used to quantitatively analyze the denoising result of the shielding filter. The results show that the proposed shielding filter has simple configuration and possesses favourable denoising effect.