Research On Monitoring Technology Of Short-circuit Capacity Of Distribution Network Based On Measurement Method

With the change of the scale and structure of modern power system,the short-circuit capacity,as the key parameter of power system operation and control,has been paid more and more attention.At the same time,the parameter of short-circuit capacity is closely related to the selection of primary equipment and the maintenance of secondary equipment.How to obtain the short-circuit capacity of power grid more efficiently and conveniently has become an urgent problem in the power industry.In order to achieve the convenience and timeliness of obtaining the short-circuit capacity of the power grid,and to ensure the reliability and accuracy of the results,this paper proposes a new online measurement technology of the short-circuit capacity of the power grid.On this basis,the prototype of power grid short-circuit capacity tester is developed for laboratory and field tests.The work of this paper mainly includes the following two parts:1)A new technology of on-line measurement of short-circuit capacity is put forward,and the measurement method of the new technology is continuously improved.This technology is based on the non fault disturbance,through the voltage disturbance caused by the switching of parallel capacitors or reactors with known capacity on the bus,the voltage vector value(including the effective value of voltage and phase angle difference)of the bus before and after the disturbance,the total active and reactive power rate value sent by the bus before the disturbance and the known capacity solution of the reactive power compensation equipment for switching operation to calculate the short of the bus to be tested Road capacity value.In this paper,the measurement method of bus voltage phase angle difference is studied deeply,and three methods of measuring angle difference are put forward respectively.Based on MATLAB/Simulink off-line simulation platform,a virtual instrument model is built for simulation analysis.2)Based on the new measurement technology,two prototypes of the tester are developed and tested on multi platform.First of all,the correctness and accuracy of the measurement principle are verified based on the off-line simulation platform of MATLAB/Simulink;then,the prototype is used in the real-time universal simulation platform of UREP to carry out the semi physical simulation test,once again verifying the correctness and accuracy of the measurement principle;then,the prototype carries out the semi physical simulation test with full coverage of short-circuit capacity based on RTDS At the same time,different calculation examples and different working conditions are set up to test the high accuracy of the tester.Finally,based on the physical dynamic experimental platform,the dynamic model verification test is carried out,including building a physical model platform to simulate the power grid,verifying customized components,carrying out short-circuit fault experiment,capacitor switching experiment and cross verification of dynamic model test and offline simulation,The test results show that the developed prototype can complete the measurement task of short-circuit capacity parameters correctly,and ensure that its measurement value has high accuracy.At the same time,field test is carried out based on the actual 10 k V substation to check the stability and convenience of the short-circuit capacity tester.