Research On Key Technologies Of Transient Recording Fault Indicator System

Fault indicator,as an intelligent electronic device that can reflect faults in time,is an indispensable tool for the intelligent construction of distribution network.For a long time,it is difficult to judge and locate the single-phase grounding fault in the low current grounding system,and it is also a problem that must be solved in the development of fault indicator.In this paper,a self-designed electric field sensor is used to measure the voltage of distribution line,and the starting criterion of fault indicator based on voltage is studied by using the measured results.The transient recording type fault indicator studied in this paper is applied to overhead lines.It consists of acquisition unit and collection unit.Three groups of transient recording type fault indicator and main station system together constitute the transient recording type fault indicator system.This paper introduces the working principle of the system in the case of short-circuit fault and single-phase grounding fault.According to the problems existing in the operation of the system,two research difficulties are summarized,which are the acquisition of line voltage and the start-up of fault indicator.Aiming at the problem of line voltage acquisition,this paper designs two kinds of electric field sensors for transient recording fault indicator.They are cylindrical electric field sensor and semi-cylindrical electric field sensor.The electric field sensor converts line voltage into sensor output voltage,and collects line voltage through non-contact measurement.The working principles of two kinds of electric field sensors are analyzed in detail,and the simulation models of two kinds of electric field sensors are built in Maxwell simulation software to verify the correctness of the theory.During the design of the electric field sensor,it is found that the change of the structure and parameters of the electric field sensor will change the response curve of the electric field sensor.Therefore,the influence of the parameters of the electric field sensor on the responsiveness of the sensor is analyzed,and the influence of several representative external interference factors on the measurement accuracy of the electric field sensor is studied.After modeling and simulation analysis,some external interference factors which seriously affect the measurement accuracy of electric field sensor are analyzed,and corresponding interference reduction schemes are put forward.Because the electric field sensor in three-phase conductor system can not avoid the interference of adjacent conductors,the output voltage of the electric field sensor which characterizes the three-phase integrated voltage is directly used in the starting criterion of the fault indicator.Two start-up criteria based on voltage fault indicator are proposed.A simulation model of 10 kV distribution network is built on the platform of MATLAB/Simulink to simulate single-phase grounding fault of 10 kV distribution line.The parameters of the protection criteria are adjusted and verified by using the obtained voltage data.