PT铁损对铁磁谐振的影响分析

Analysis of PT Core Loss Effects on Ferroresonance

通过实测PT的参数,采用最小二乘曲线拟合的方式确定PT模型的特征曲线和铁损。分别对中性点直接接地系统和不直接接地系统的铁磁谐振现象进行分析,从理论上证明了PT的铁损对铁磁谐振的阻尼作用。利用MATLAB分别对两种系统进行仿真,研究在不同的谐振条件下,PT铁损的变化对谐振的影响。仿真结果表明,在各个谐振区域,这种影响都存在。PT的铁损越小,谐振越容易发生,产生的过电压越高,持续时间越长,这在中性点直接接地系统中尤为显著。仿真结果同理论分析相吻合。

The characteristic parameters of PT are calculated by processing the test data in the least squares curve fitting methods. Based on equivalent model of PT, this paper analyzes the reduced equivalent circuits to the power system with earthed and non-earthed neutral respectively. The act of PT core loss on damping ferroresonance intensity and persistence is proved theoretically. The simulating tool of MATLAB is then applied to calculate the effects in both systems, which are caused by changing core loss of PT at different condition of ferroresonance. From the results, it is shown that the influence exists under all of the conditions and is more remarkable in the earthed neutral power system. The lower the core loss is, the intenser the resonance is, the higher the value of overvoltage caused is. The results are in good agreement with the analysis concluded in theory. It is also helpful to design suitable equipment for suppressing resonance in different types of power system.