电流互感器暂态特性试验用标准信号的参数估计

Parameter Estimation of Standard Signals for Transient Characteristics Test of Current Transformer

电流互感器的暂态特性是影响继保装置正确动作、攸关系统安全稳定的关键因素之一,对入网的电流互感器开展暂态特性试验或检测具有重要意义。为准确掌握试验用标准信号的信息,提出了相应的参数估计方法。在噪声允许的范围内,求标准信号的正极大值。结合暂态发生的时间信息,截取出暂态时段内的各个正极大值,再利用对数变换将其转换为直线函数,使用最小二乘法拟合得到直线的截距与斜率,分别对应暂态电流的幅值及时间常数。仿真结果表明:当标准信号的采样频率为6.4 kHz并伴有20 dB高斯白噪声时,所提方法能精确估计出暂态发生时刻,对暂态电流时间常数的估计精度高于暂态电流幅值,暂态电流时间常数的估计范围为80?210 ms。所得结论为开展电流互感器的暂态特性试验提供了参考依据。

Transient performance of the current transformer（CT） is one of key factors that relates to the security and stability of power grids and whether the protective relaying could be operated correctly, so it is of great significance for grid-connected CT to perform transient performance test or detection. To master the information of standard signals for the test, corresponding parameter estimation method is proposed to solve the positive maximum of standard signals within the allowed noise range. Combining with the time information when the transient process happens, positive maximums within the transient time period are captured, then they are transformed into linear function by logarithmic transformation, and then using least square fitting both intercept and slope of the linear function are obtained, which correspond to the amplitude and time constant of transient current respectively. Simulation results show that when the sampling frequency of the standard signal is 6.4 kHz accompanied with 20 dB of Gaussian white noise, using the proposed method the moment when the transient happens can be estimated accurately, and the estimated accuracy of transient current time constant is higher than the estimated accuracy of transient current amplitude, the estimation range of transient current time constant is from 80 ms to 210 ms. The obtained results are available for reference to the CT transient performance tests.