Method For Measuring Ground Parameters Of Medium Voltage Distribution Network Based On Arc Ground Fault Characteristics

The distributed capacitance and insulation resistance of the line are two important technical parameters for the normal operation of the medium voltage distribution network,which determines the reliability and safety of the power supply.Cable insulation aging can cause single-phase grounding faults and even personal electric shock,which seriously damages the reliable operation of the distribution network.Accurately grasping the insulation state of the cable and the distributed capacitance to the ground have a great significance in actual production.Aiming at the problem that the existing method affects the normal operation of the system in the process of measuring the parameters of the ground,and is affected by the operation mode of the system,it can’t be monitored online for a long time.The paper starts from the characteristics of the distribution network and studies the parameters of the line to the ground and the distribution network.The intrinsic link between the transient faults that exist,and the feasibility of using the instantaneous fault data to measure the ground parameters.Aiming at the arc signal,the fault signal is seriously distorted,and the signal contains rich information on the ground parameter information.The signal analysis method suitable for the distortion voltage and the distortion current is selected.On this basis,the Fryze distortion power decomposition method is used to analyze the fault signal,and the information related to the ground parameters is directly extracted in the time domain.Distorting the zero-sequence current into distorted active current,distortion reactive current and electric blunt current according to the distortion zero-sequence voltage;Based on the analysis of the transient single-phase ground fault characteristics,the Fryze&Hilbert transform is used to directly solve the zero-sequence equivalent conductance of the equivalent susceptance of the ground-distributed capacitance from the perspective of distortion power.The wave correction factor improves the measurement accuracy of the cable’s distributed capacitance to ground.Finally,the measurement algorithm and implementation scheme of the grounding parameters of the medium voltage distribution network are designed.The simulation model of lOkV medium voltage distribution network is established in this paper.The correctness of the proposed method is verified by simulation of different grounding methods and different fault types.The ground-parameter measurement method based on transient fault information proposed in this paper can simultaneously measure the line-to-ground capacitance and insulation resistance of the system for safe operation,and has the advantages of wide application range,safety,economy and easy implementation.