基于高低频段暂态信号相关分析的谐振接地故障选线方法

Fault Line Selection Method in Resonant Earthed System Based on Transient Signal Correlation Analysis Under High and Low Frequencies

针对谐振接地系统在相电压过零点附近发生单相接地故障时选线灵敏度不足的问题,提出一种基于高低频段馈线零序电流与母线零序电压导数的相关分析故障选线法。系统故障后健全线路的阻抗在高低频段均呈电容特性,而故障线路的阻抗在高频段呈电容特性,在低频段呈电感特性。由此可知,健全线路零序电流与母线零序电压导数的相关系数在高频段和低频段相等,其差为零;故障线路在低频段含有衰减直流分量,该频段内零序电流与母线零序电压导数的相关系数很小,而高频段的相关系数数值较大,两者差值较大。根据这一特点构成故障选线判据。该方法物理意义明确,能提高相电压过零点附近的选线灵敏度,在其他故障状态下也能准确选线。大量仿真结果验证了该方法的有效性。

In order to overcome the inaccurate selection of faulty line of single‐phase grounding fault when the phase voltage passes zero in resonant earthed system , a method of correlation analysis is proposed based on zero sequence current of lines and zero sequence voltage of bus both in high and low frequency bands . After the single‐phase ground fault appeared in the system , the impedance of the sound line shows capacitance characteristics in the high frequency and the low frequency band . With respect to the impedance of the faulty line , it shows capacitance characteristics in the high frequency band and inductance characteristics in the low frequency band . So , the correlation coefficient of the zero sequence current of the sound lines and the derivative of the bus zero sequence voltage are equal both in the high and the low frequency band , and the difference is zero . Because of the existence of decaying DC component in the faulty line , the correlation coefficient of the zero sequence current of the faulty line and the derivative of the bus zero sequence voltage is very small in the low frequency band , while the correlation coefficient in the high frequency band is large as is the difference . So , the fault line selection criterion can be formed by the characteristics . The method has clear physical meaning , the sensitivity of fault line selection can be improved near the zero ‐crossing point of the phase voltage , and the fault line selection in other fault conditions also can be achieved accurately . A large number of simulation results show the feasibility of the method .