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. This work is supported by National High Technology Research and Development Program of China(863 Program)(No. 2012AA050215).