XLPE电缆局放脉冲频谱分析及传感器选频

Spectrum Analysis of the Partial Discharge Pulses in XLPE Cable and Frequency Band Selection of Sensors

为选择好局放测量传感器的频带，用指数衰减函数、梯形函数、高斯函数和三角函数数学描述了交联聚乙烯（XLPE）缆中的局放脉冲并定量分析了局放脉冲的上限频率，其结果和实测局放脉冲经快速付里叶变换后的频谱基本吻合。用最小二乘法拟合信号各频率分量在XLPE电缆中的三特性并给出最优表达式后，把输出信号和输入信号比值在0．7～1范围内作为局放能量的集中区域，在此区域内得到检测不同长度XLPE电缆局放所需传感器的频带要求。对于5m长的电缆接头，传感器上限频率需〉168．9MHz，较长电缆局放测量则需数十MHz。

The exponential attenuation function, trapezoidal function, Gaussian function and circular function are used to describe the partial discharge （PD） pulses in XLPE cables, and the upper frequency limit of the PD pulses is analyzed quantitatively, which matches well with that of the detected PD pulses after FFT. The least squares techniques are used to fit the attenuation characteristics of different frequency component in XLPE cables and the best expression is given. Considering ratio of the output signals magnitude and the input signals magnitude from 0. 7 to 1 as the focus energy range of the PD pulses, the bandwidth of sensors is advised in this paper when detecting the partial discharge of XLPE cable with different length. For a 5-meter-long cable joint, the upper frequency limit of sensors should be not less than 168.9 MHz and the bandwidth is several tens MHz when PD is measured in longer cables.