Research On Single-phase Grounding Fault Location Technology In Distribution Network

In order to enhance the reliability of power supply system, the neutral point non-solidgrounded is applied in the distribution network of our nation. However, for a long time therehas not been a solution to locate the single-phase ground fault because of weak current whenthe system has a single-phase ground fault. At present and at many places, they still adoptmanual switching and artificial patrolling to locate the fault point, resulting in longtime powercut, heavy overhaul overload and high expense. So the research of locating the Single-phaseground fault of power supply system is manful in theory and reality to enhance the reliabilityand ensure the safety.Firstly, the paper analyses and compares the change features of the current’s stable andtemporary conditions after the single-phase grounding fault happened. In condition of the fault,the stable condition signal is weak because of the Compensation effect of Arc suppression coil,then accuracy of adopting stable condition signal to locate the fault is low. Comparing with thestable condition weight, the temporary condition weight is enhanced obviously. Therefore, thelocation of the fault based on temporary condition signal is more favorable to overcome theeffect that Arc suppression coil has made.In view of the position-sequence and negative-sequence aren’t effected by the Arcsuppression coil, the paper raises a new way to locate the fault based on the Transient complexsequence current. Delimiting plus position-sequence and negative-sequence fault weight iscomplex sequence current. The complex sequence current flows from fault point to system side,so the complex sequence current in fault zone is much more than that in normal zone. Thecomplex sequence current method can locate the fault by comparing the complex sequencecurrent in different zones. The method is not effected by Arc suppression coil and distributedcapacitance, and its ability of anti-transition resistance is good, in a while its demand ofsynchronism is low.Aim to situation which has zero sequence current and voltage mutual inductor, we raise themethod of transient combination admittance. We choose three forms of frequency which has themost reactive power from specifically frequency parts, and then combine the angles of the threefrequencies according to their reactive power percentage. The location of fault can be brought about according to the difference of admittance’s angle in different detection points. This methodis applied to system which is Neutral Point suppression coil grounding. The emulation resultsverify the correctness of the method of transient combination admittance.It raise a overall scheme that ante-location of single-phase-to ground fault in small currentgrounding system based on the theory research, and it also discussed the power mode of FTUunit and means of communication of system, finally, it elaborates the Functional structure andworkflow of fault-ante-location system. All of above lay the foundation for the development ofthe follow-up of the physical prototype.