Study Of Fault Location Method In Small Current Grounding System

With the rapid development of the economic and industrial construction, the demand for electric power is increasing, and the distribution network is becoming more and more intensive. Only with reliable operation of the power can guarantee the smoothed domestic product production and people’s normal life, and the different operation modes of power system is related to the reliability of power supply, the safety of equipment and economy of operation. Medium-voltage distribution network in our country is nearly neutral non-effectual grounded system. However, the small fault current, the unstable arc characteristics, flexible and reliable operation mode of the neutral non-effectual grounded system and the extremely complicated fault situation had made it difficulties to determine fault location point after the single-phase-to-ground fault, which is still the most urgent problem up to now.Based on the feature that zero-sequence admittance measurement modulus of the fault point switches at both ends differences evidently, a novel fault location method, i.e. absolute maximum value method of zero-sequence measurement admittance modulus difference is first proposed. In this method, the fault parameter of steady state is defined, calculating the fault parameter of each segment in order to determine the failure criterion, and the biggest fault parameter of the two adjacent detection point can be considered as the fault segment. At the same time, the failure criterion is respectively simplified according to neutral resonant gounded power system, neutral un-grounded power system and neutral high-resister gounded system, which improves the positioning accuracy. The introduction of subtracted fault parameter effectively eliminated the measurement error, and the simulation results via ATP-EMTP demonstrate that this method has good adaptability, strong anti-interference ability and high location accuracy, which is suitable to a variety of different small current grounding systems.By use of the feature that zero-sequence admittance measurement modulus of the fault point switches at both ends differences evidently, a novel fault location method, i.e. absolute maximum value method of zero-sequence measurement admittance modulus difference is secondly proposed. The method has adjust sample clock modified the original correlation coefficient and threshold of the transient zero-mode power signals on both sides of the detection point. A large number of simulation experiments show that the method could be applied extensively, hardly be affected by the structure of the system and the neutral point grounding mode, and can effectively adjust the fault criterion by using DA system, which greatly improves the correct rate of location and lays a good foundation for the research and practical application of fault location in small current grounding system.