Based on the voltage variations,a new approach called ‘lower threshold value,more criterions’ was proposed to enhance the single-line-to-ground fault detection sensitivity in neutral un-effective gounded system. The zero sequence voltage, fault phase voltage and un-fault phase voltages would change simultaneously when the single-line-to-ground fault happened in the system. The variations of the voltages were in different fixed intervals considering the effect of fault impedance and fault distance. Then the fault detection method based on the several voltage variations was proposed. The algorithm based on many voltage variations avoids being affected by normal operations of system and the small features of fault, and the sensitivity of the fault detection was enhanced by lower threshold. It could be used for the high impedance fault detection. The enhancement of anti-interference and anti-fault-resistance of the algorithm was proved by the large numbers of simulations using PSCAD/EMTDC program. The method is beneficial to the accurate and reliable single-line-to-ground fault detection.
