Research On Non-contact Measurement Technology Of Bus Voltage In Switch Cabinet

Voltage measurement is a key link in the process of safe and stable operation of the power system,and has a decisive influence on electric energy measurement and relay protection.At present,most of the distribution network lines connected by distributed power sources are not put into line reclosing or only put into normal reclosing mode,which is not conducive to timely transmission of power to the line,and directly affects the automatic power restoration function of the distribution network.Due to space constraints,the substation cannot install a voltage transformer on each 10 k V line.If a voltage transformer is installed in the switch cabinet,the transformer has high requirements on the installation conditions in the cabinet due to direct contact with the wire to obtain electricity.And it increases the equipment failure rate.In addition,with the development trend of miniaturization and compactness of the switchgear,the busbar voltage measurement of the switchgear is also facing the development needs of miniaturization,digitization,and intelligence.In view of this,this article proposes to use the indirect measurement method to measure the spatial electric field generated by the bus voltage of the switchgear,so as to realize the non-contact measurement of the measured voltage.The main work of this paper is as follows:(1)According to the structure and main technical parameters of the 12 k V armored removable AC metal-enclosed switchgear,this paper establishes a three-dimensional transient electric field finite element simulation model of the switchgear busbar room and cable room in the electromagnetic field of the finite element calculation software Ansys.Then the paper calculates the electric field distribution characteristics and electric field concentration area of the busbar room and the cable room under the nominal voltage of the10 k V system.Indeed,the software field post processor is used to view the specific values of the electric field strength at each position in the calculation area,so as to provide a data basis for the following integration operations..(2)In the steady-state temperature field of the finite element calculation software Ansys,considering the skin effect on the heating of the conductor,this paper comprehensively calculates the power loss of the main heating source conductor in the cabinet at 1.1 times the rated current,and obtains the switch cabinet busbar room,cable The temperature distribution of the room during operation,so as to provide a basis for later considering the influence of the ambient temperature on the electric field distribution and the numerical value of the electric field intensity in the switchgear.(3)In order to realize the non-contact measurement of the busbar voltage of the high voltage switchgear,taking the voltage measurement of the branch busbar in the cable room as an example,this paper applies Gauss Legendre integration algorithm and Chebyshev integration algorithm to measure the electric field intensity between the branch busbar and the bottom of the metal shell.According to the electric field distribution law under the branch bus,this paper re-divides the integration algorithm interval into two intervals as an improvement,and optimizes the integration calculation by summing the results of the two intervals.According to the simulation results,the improved Chebyshev integration algorithm restores the bus voltage accuracy slightly better than the improved Gauss Legendre integration algorithm.(4)Because the change of bus voltage and environmental factors may affect the electric field distribution on the integration path,this paper considers the influence of different bus voltages,three-phase voltage amplitude or phase imbalance,and ambient temperature and humidity on the electric field integration.This paper analyzes the electric field distribution law on the integration path and the result of the integration algorithm to restore the bus voltage under different initial conditions,further verifying the feasibility of the electric field integration method to restore the bus voltage.