A small current neutral grounding fault location method based on the direction of
transient state reactive power is characterized in that change of
voltage or current serves as a failure starting condition, and after the starting, the zero sequence
voltage is taken as the participating
voltage if a detection point can be used for detecting the zero sequence voltage and if not, the following steps are performed: 1, confirming the fault phase as per characteristics of three
transient state line voltages, and 2, confirming the
transient state line voltage including the fault message as per the type of the fault phase, taking the transient state line voltage as the participating voltage, confirming the characteristic frequency range, and further building a
digital filter to filter the participating voltage and the zero sequence current
signal, so as to obtain the component within the characteristic frequency range; and then confirming the direction of the reactive power of all the detection points through utilizing the components of participating voltage and the zero sequence current within the characteristic frequency range, so as to further confirm the fault section. According to the invention, the transient voltage and current signals as well as zero sequence voltage and line voltage are utilized at the same time, the positioning reliability is higher, the adaptability is stronger, quick direction protection for ground fault of all the voltage classes is applicable at the same time, and the protection speed and reliability are taken into consideration.