Research On Neutral Point Of 10kV Power Grid By Non - Linear Resistance Earthing

The 10 kV voltage grade is the major way used in urban distribution network. There are three common ways used in grounding the neutral point-ungrounding method, arc suppressing coil grounding method, resistance grounding method. As the city line change from over-line to cable line, increasing the electric capacity and current in the system, these current grounding methods can’t meet the needs of limited over-voltage and decreased fault current. As a result, the new type of grounding method named the neutral point grounding with nonlinear resistance become the research direction in neutral point grounding field.First of all, study the background and development about neutral point grounding. Based on PSCAD(Power System Computer Aided Design) software, establish a model comparing and analyzing the current and waveform about traditional grounding method with grounding with nonlinear resistance, to validate the technical feasibility.Secondly, establish the hybrid model of neutral nonlinear resistor and arc suppression coil grounding. In order to restrain the arc grounding overvoltage and reduce the fault current, on the basis of the neutral point of nonlinear resistance grounding model, build the new modified model. Through stimulating the overvoltage of single-phase grounding fault current and arc voltage, the mixed grounding mode has obvious inhibitory effects on the arc grounding voltage and the fault current is significantly reduced.Finally, reduce the influence on people and equipments. Through coordinating with relay protection equipment, neutral point grounding with nonlinear resistance method and hybrid method effectively inhibit the over-voltage, which reducing the influence on people and equipments.All in all, this grounding method has feasibility in technology and will be the development trend in the neutral grounding field.