Characteristics Analysis Method And Technology Development Of Distribution Network Single Phase Grounding Based On Physical And Simulation

Distribution network is an important part of power system.With the continuous expansion of power network coverage area,the risk of step voltage electric shock caused by single-phase grounding accident in distribution network becomes more and more prominent.The grounding current is the direct factor affecting the degree of electric shock.Accurate calculation of grounding resistance at fault point and construction of step voltage calculation model after accident are the premise of studying electric shock risk assessment technology.In this paper,the influence of non-effective contact between grounding electrode and soil is fully considered,and the calculation formulas of contact resistance and grounding resistance of conductor falling on the ground at any buried depth are derived.The fault current formulas under different grounding modes after single-phase wire break is derived by using circuit analysis theory.The field-circuit coupling calculation model is established by combining the dispersion field and human body circuit.Finally,MATLAB software is used to realize the algorithm programming of the calculation model.The model is verified by Simulink,multi physical field simulation software and experimental test.The error of grounding current between the calculation results and Simulink is less than 2%;the error of grounding resistance between the calculation results and multi physical field simulation software is less than 5%;by comparing the measured,simulation and calculation results,the error both of grounding resistance and grounding current is less than5%,and the error of step voltage is less than 10%.Combined with the measured data and calculation formula of grounding resistance,an indirect calculation method of contact layer parameters between conductor and soil is proposed,and the equivalence between proportional test and 10 k V real fault is analyzed.Based on the test platform,and combined object with simulation,the characteristics of single-phase wire broke grounding fault in distribution network are analyzed.The influence of the length of the conductor,the buried depth of the conductor,the soil resistivity,the resistivity of the contact layer,the thickness of the contact layer and the change of the contact resistance on the grounding current and step voltage are analyzed in detail.Based on the physiological reaction and harm degree of human body after different electric shocks,the risk assessment technology of single-phase wire broke grounding fault in distribution network is developed,and the risk level of electric shock is divided.The software and hardware platform of risk assessment based on actual parameters is developed,and the evaluation results of the platform are verified,and the error is less than 10%,which meets the engineering requirements.The hardware platform can realize the simulation of different fault conditions and the effective measurement of step voltage.The software platform can carry out real-time risk assessment on the measured data,and can also realize the off-line assessment of electric shock risk combined with the calculation model constructed in this paper.