Research On DC Bias Current Calculation And Monitoring System Of Transformer Under The Influence Of Metro

Metro adopts DC traction power supply mode.Stray current between rail as the return current path of traction current and the earth will cause DC magnetic bias of transformer and endanger the safe operation of the power system.In view of this,the design of computer monitoring system for transformer DC bias under the influence of Metro is put forward to provide mechanical support and theoretical reference for Metro Planning and operation,power system dispatching and operation.This paper mainly studies the following aspects:Firstly,existing monitoring data of DC bias of main transformers in urban thermal power plants are analyzed,and the characteristics and regularities of DC bias current of transformers under stray current are revealed.On this basis,the numerical model of stray current distribution and surface electric field distribution caused by stray current during metro operation and the model of magnetic bias current of main neutral points in urban areas are established,so as to select and monitor the stray current.Site preparation.Secondly,modular design of DC bias monitoring system for urban main transformer is carried out,including data preprocessing sub-module.Data calculation sub-module,magnetic bias current data monitoring sub-module and data communication sub-module.Software design of monitoring system based on MATLAB and SQL Server is carried out.Data transmission is carried out by traditional communication mode and cloud computing platform,and finally a bias is formed.The overall design framework of magnetic current monitoring system.Finally,taking Urumqi Metro and urban power system as examples,the magnetic bias current level of the neutral point of the main transformer is calculated and evaluated,and a monitoring system.Finally,taking Urumqi Metro and urban power system as examples,the magnetic bias current level of the neutral point of the main transformer is calculated and evaluated,and a regional DC magnetic bias monitoring system is installed at the site with magnetic bias risk.The system has the functions of data monitoring,storage,early warning and upload communication.It has friendly interface,easy operation,scalability,simple installation and configuration,and is also compatible with SCAD of the power system.System A is directly locked and can store data in the database of power system operation parameters.The monitoring results to verify the calculation results,prove the usefulness of the monitoring system,and also prove the correctness of the estimation of the bias current level.The research results in this paper can provide a theoretical analysis basis for DC bias phenomenon of main transformer in an urban area,and also provide the operational basis for dispatching operators of urban power system in actual project maintenance and dispatching.