A Study On On-line Monitoring System For Core Grounding Current Of Power Transformer

The power transformer is an important equipment of power transportation and power transformation,the operating condition of the transformer affects the security and stability of power grid operation.Despite the current operating conditions of some important equipment in substation has some online monitoring methods,such as main transformer oil online monitoring system of transformer partial discharge on-line monitoring,on-line monitoring of partial discharge in GIS.But for the power transformer core earthing current there is no better comprehensive online monitoring and analysis methods and equipment,at present still rely on the substation operating personnel regularly measured can not meet the core grounding current on-line,real-time monitoring and management requirements.This paper is based on the transformer core grounding theory,design a set of power transformer core ground current online monitoring system.The system includes client and host computer,PLC is the current acquisition unit based on STM32,according to the size of the current limiting resistor to realize automatic switching,prevent iron core multipoint grounding grounding lead core overheating and causing the current exceed the standard and burnt fault.The change range of iron core earth current,therefore,before using the A/D conversion of analog multiplexers,the preprocessing of the current signal program-controlled amplifier and filter,D/A conversion with first-order difference method to eliminate the sampling data in the singular,and the discrete data are smoothed by five point three times smoothing method.The degree to ensure the accuracy and reliability of data.The computer is mainly using programming language Visual C# and GDI+ graphic object oriented design the man-machine interface,the main interface includes the query interface login interface,system interface,real-time monitoring data and historical data interface.Login interface is mainly in order to facilitate staff login system;the main interface of system mainly shows the main function of the system;real-time monitoring interface data real-time display curve of core grounding current changes;historical data query interface is mainly displayed in the form of digital core grounding current.PC interface is also provided with an alarm information system according to the client to upload real-time data and historical fault information,the current value and the grounding resistance of the comprehensive value to judge whether the normal operation of thetransformer,to achieve real-time online monitoring and fault diagnosis for the purpose.