基于3δ滤波的介损角算法

Dielectric Loss Angle Algorithm Based on 3δ Filter

脉冲噪声的干扰、信号频率偏离正常值导致的频谱泄漏和栅栏效应会给介损角测量造成误差。为此,提出了一种能有效抑制脉冲噪声和非整周期采样给介损角测量造成误差的算法:用3δ算法抑制电压和泄漏电流信号中的脉冲噪声;对处理后的信号使用改进的基波相位分离法计算介损角,能高精度获得介损角、且计算量较小。对频率为50.5Hz、含有脉冲干扰的电容型设备的电压和泄漏电流信号的计算结果表明:无论是滤波前后,改进基波相位分离法较之DFT算法均具有更高精度;两者滤波都具有一定的效果,滤波使改进的基波相位分离法400次计算所得误差的绝对值的最大值、绝对值的均值和均值分别从0.01990、0.00412和-0.00026rad减少到0.01464、0.00327和0.00006rad。从而验证了该方法能抑制脉冲噪声和非整周期采样给介损角测量带来的误差。

Voltage and leakage current signals for dielectric loss angle measurement are easy to be interfered by impulse noise, which will cause large error of dielectric loss angle measurement. And signal frequency deflection from normal value will cause spectral leakage and fence effect, and will bring about measurement error of dielectric loss angle. Therefore, the paper proposes an algorithm that can decrease the error caused by impulse noise and non-integer period sampling. Firstly, the algorithm use 3δ rule filter algorithm to suppress impulse noise of sampled voltage and leakage current signals, then the processed signals are calculated by the modified fundamental harmonic separation algorithm, and the algorithm not only gets more accurate dielectric loss angle, but also has less calculation quantity. Voltage and leakage current signals of capacitive electrical equipment are constructed, which have impulse noise and frequency is 50. 5 Hz. The results indicate that： the modified fundamental harmonic separation algorithm has smaller error than DFT algorithm; calculation results of filtered signal have a higher accuracy than those of unprocessed signal regardless of DFT algorithm or modified fundamental harmonic separation algorithm, and 3δ filter algorithm makes the maximal absolute value of 400 times calculation error to decrease from 0. 01990 rad to 0. 01464 rad, the mean absolute value of 400 times calculation error to decrease from 0. 00412 rad to 0. 00327rad, and the mean value of 400 times calculation error to decrease from -0. 00026 rad to 0. 00006 rad. Those indicate that the algorithm proposed by the paper not only can suppress dielectric loss angle measurement error caused by impulse noise, but also can alleviate the error cause by non-integer period sampling.