Design Of Virtual Instrument-Based Calibrator For Power Transformers

Power transformer is an indispensable part in the power system. It is very significant that accurate and quick measurement of the power parameter for the power dispatching automation and guaranteeing power system security and economic operation of power network. Therefore transformer calibration research about the accuracy grade has also become a research hotspot.With the rapid development of computer hardware and software technology, measurement system has begun to develop in this direction. Virtual Instruments is the perfect combination of the modem computer technology, the instrument technology and other new technologies. Through a data acquisition card, it will measure the analog signals into digital signals and the software can replace all the hardware equipment to achieve the various functions which is its extraordinary character. It is a fully computer-based equipment. With a data acquisition card and LabVIEW software development platform, it can achieve all the traditional instruments.Transformer calibration system design in this paper is based on virtual instrument technology. Using LabVIEW as the main programming language, this system fully achieves the design thought: "software is instrument". By virtue of PCI-6221 data acquisition card and the computer as the hardware platform in the VI, the program achieve the functions of data acquisition, data analysis and processing, preservation of the parameters and the results, curves drawing and report generation, and so on. One part of the data-processing algorithms calculates the signals' phase error and ratio error by using correlation function algorithms. In accordance with national measuring transformers test limits of errors, it can judge the accuracy grade of the transformers be measured.After connecting lines connection of the standard mutual transformer and the test transformer , together with a particular self-made signal conditioner board, testing personnel can directly to test the accuracy grade by this calibration system.The design makes full use of computer software and hardware's advantages, to achieve the functions of data automated acquisition, data analysis and processing. It can not only achieve the effect of traditional instruments, but also be more convenient and flexible. In addition it has a strong extendibility, so users can modify or increase calibrator's functions upon their own demands.