【摘要】 介绍了电容型设备介质损耗因数在线监测的原理以及监测系统的组成,分析了测量结果的误差来源以及提高测量精度的方法,以谐波分析法为基础,采用基于DSP的跟踪频率变化交流同步采样技术,确保每个周期采样128个点,用快速傅里叶变换(FFT)求出电压、电流信号基波傅里叶系数,通过RS-485总线传给上层变电站信息管理系统。考虑到FFT的泄漏效应和栅栏效应,采用加多项余弦窗算法对FFT进行修正,提高其准确性。更多还原

【Abstract】 The principle and construction of on-line monitoring of the dielectric loss of a high voltage capacitive apparatus are discussed in this paper. Then the error sources and the methods of improving the measuring accuracy are analyzed. At the same time, on the basis of the harmonic analyzing method, the DSP technology is used to track the variation of frequency to ensure the sampling of 128 dots per cycle. Then the fast Fourier transform (FFT) is adopted to calculate the Fourier coefficients of the fundamental waves of both the normative voltage signal and leakage current. Moreover, it is easy to figure out the dielectric dissipation factor by finding the phase angle difference between the fundamental waves. The factor is uploaded to the upper level information management system via RS485 interface. By taking the influence of the leakage effect and the barrier effect into account, the poly-cosine window algorithm is employed to increase the accuracy of FFT.更多还原