Study On Digital Metering System Of Transformer Substation

Current and voltage are elementary parameters in power system. As new measuring instruments, electronic current transformer (ECT) and electronic voltage transformer (EVT) have been rapidly developed recent years attributing to their remarkable advantages: smallness,lightness,no ferromagnetic saturation,board band width and compatibility with interfaces of microprocessor based protection. But, the lack of the metering and protecting technology deeply restricts the development of electronic transformer.The direct object of power metering is electronic transformer. From IEC standards, electronic transformer has two kinds of output: digital signals and analog signals. Power metering system which based on the digital output of electronic transformer can eliminate the error in transmission abstractly. At the same time the additive error which brought from temperature or extended excursion is disappeared. Therefore, the research of digital metering technique and system can accelerate the development of electronic transformer consequentially.This thesis introduces the development of electronic transformer and the significance of digital metering technique and system. After introducing the structure of the electronic transformer, the thesis analyses the details about data acquisition system and the digital output interface of merging unit. Then, the whole design of digital metering system and the function of each part are introduced. Based on the analysis of the standard IEC61850-9-1 and the working process of network card, the thesis gives the solution to the digital input interface. To the data, the thesis compared some kinds of digital metering arithmetic, presents the quasi-synchronization DFT arithmetic after considering the accuracy, security, calculational capacity and speed. Finally, each kinds of mentioned metering arithmetic is emulated and the error estimation is also made.