Fault Line Selection And Location Study For Small Current Neutral Grounded Via Arc Extinguishing Coil System

In the electric power system, the system which voltage grade less than 60 kV is known as the small current grounding system, and this kind of system often used the operation mode of neutral non-effective grounding.In this mode, if single-phase earth fault happens, the system can run 1 or 2 hours because the phase voltage is still symmetry, and the ground current of fault phase is small.But single-phase earth fault will cause the increase of non-fault-phase’s voltage. Long time of grounding operation will easy to make fault expanded to two point or more earth short circuit, and even lead serious interphase short circuit fault.Therefore, in order to prevent more serious fault cause by single-phase earth fault.it necessary to find out the fault line and ground fault point as soon as possible.Because the single-phase earth fault signal of in the small current grounding system is small, firstly, the voltage change discriminant method is used to select the line of fault system. Then use the fault location method which base on zero-sequence current to find the fault point.The principle of this method is that when single-phase earth fault happens, the zero sequence current mutual inductor which is installed on the designated line is used to measure the current value. Then the data is sampled Synchronously and transmited to the control center through GPRS,the fault area is found by the GPS.Finally, after the ascertain of the fault area and fault line, using special positioning equipment to positioning the fault location.The paper using the KA2003-DW small current grounding system single-phase earth fault positioning device.In this method, it don’t need additional signal but only collect data of the lines in distribution network itself. So there is no effect on system operation. And a model is set up by Matlab simulation to verify the method above. The results indicate that the method of using zero sequence after the fault occurrence to realize the lines selection and positioning of the ground fault of small current grounding system single-phase earth fault is effectly and feasibly.