基于分段拟合算法的电流互感器误差研究

Research on the error of current transformer based on subsection fitting algorithm

电流互感器的传变误差直接影响继电保护动作的可靠性。然而利用现场测试数据无法直接预估大倍数短路电流时的励磁电流,很难对传变误差作定量评估和确切计算。提出利用三次样条插值和指数函数综合解析表达式,对原始数据分段处理拟合伏安特性曲线,可完整描述线性区和饱和区伏安特性,准确求出饱和区内的励磁电压和励磁电流值,从而计算出大倍数短路电流时电流互感器的传变误差和二次最大允许负载。通过与多组实测数据比对,验证了该算法拟合精度高,计算结果准确,具有较好的工程应用价值。

Proper transform of Current Transformer（CT） is the precondition for the proper operation of protective relays. However, the field test data can not be directly used to predict the excitation current when large short circuit current, it’s hard to make a quantitative evaluation or exact calculation of CT error. A comprehensive analytic expression of three spline interpolation and exponential function is proposed. It uses a subsection processing to fit I-V character curve, which can completely describe the linear and saturation regions of I-V character and obtain the excitation voltage and current value of the saturated region, thus it can calculate the transmission error and the maximum allowable load of the current transformer when short circuit fault occurs. After verification with the measured data, the measured data can be well fitted and the calculated results are accurate. Results show it has a good engineering application value.