Anti-polarity of zero sequence CT leads to the failure in NES fault line selection, after analyzing the reason, a new selection approach using approximate entropy of ground admittance is proposed. Difference method is used to improve matrix pencil and solve the problem of component annihilation, therefore the pole information of complex frequency domain is got accurately. Evaluating the approximate entropy of distribution capacitance of each feeder under arc suppression coil compensation effect, then it is discriminated as fault feeder when the numerical value is beyond a threshold value. The method eliminates the error due to the limitation of anti-polarity of zero sequence CT and can also be applied to system with two feeders. Experimental results show that it can increase the accuracy and dependability of fault line detection effectively.