大容量试验短路电流波形参数的测算

采用抛物线拟合方法计算大容量试验短路电流波形的峰值和对应的时间坐标。理论证明短路电流波形上相邻两峰值的时间坐标中点的电流值近似等于此时的直流分量值,并据此给出波形的直流时间常数、交流(基波)分量有效值和直流分量百分数的算法。使用STL提供的标准短路电流波形,对文中算法和现有算法进行了对比测试。测试结果验证了该算法的准确性,同时表明,仅使用3个峰值点并未显著降低文中算法在计算交流分量恒定的短路电流波形参数时的准确度。通过计算直流时间常数不同、频率和交流分量有效值随时间变化等STL标准波形在每一个峰值点处的参数,得到该算法在计算峰值、直流时间常数、交流分量有效值、直流分量百分数时的相对扩展不确定度分别为0.03%、0.20%、0.40%、0.80%。

Measurement and Calculation of Short-circuit Current Waveform Parameters for High Power Tests

The parabolic curve fitting method is used to calculate the peak value and the corresponding time coordinate of short-circuit current waveform in high power tests. It is proved theoretically that the current value at the midpoint of the two adjacent peaks in the short-circuit current waveform is approximately equal to the DC component atthis time. A algorithm to calculate the DC time constant,the RMS value of AC(fundamental)component and the percentage value of DC component is given accordingly. Using the standard short-circuit current waveform provided bySTL,the algorithms of this paper and the existing ones are compared and tested. Test results verify the accuracy ofthe algorithms in this paper,and show that using only three peak points does not significantly reduce the accuracy ofthese algorithms when calculating short-circuit current waveform parameters with constant AC components. The relative expanded uncertainties of these algorithms in calculating the crest value,the DC time constant,the RMS valueof AC component and the percentage value of DC component are 0.03%,0.22%,0.39%,and 0.76% respectively,which were obtained by calculating the parameters of the STL standard waveforms at each peak point,whose DCtime constants different,frequency and the RMS value of AC component change over time.