The Study Of Calibration Device And Method For Electronic Transformer

Transformer is a converting device for current or voltage. The high voltage or current is converted into a standard current or voltage, in order to the meters measuring or the devices protecting. However, with the application of digital substation and its intelligent, the traditional electromagnetic transformers can’t keep up with the pace of the development of digitalization, which obtained the rapid development of electronic instrument transducers and applications. Not only electronic instrument transducers with a traditional transformer but with small size, light weight, good security and good linearity, meet the requirements of digital substation.The output of electronic transformers is divided into analog signals or digital signals. Transformer with analog signals is used for the meters which input is analog signals, transformer with digital output is used widely, the researchers for calibration device or method will be more, while the output of analog signals is intermediate links for digital signals, so studying the calibration method for transformer with output of analog signals have great significance. It is very different between electronic transformer and electromagnetic transformer on structure, traditional calibration methods are not up to the calibration of electronic transformer, so must study new calibration method. Calibration method has digital calibration method and analog calibration method, Digital calibration method is divided into the direct comparison and measurement difference method.Digital calibration method is adopted in this paper. Two signals from standard sampling transformer and transformer tested with a synchronized manner respectively, then send it into PC software for direct comparison, the amplitude difference and phase difference of electronic transformer is calculated. PC software is written by Lab VIEW, while errors will be showed in the way of a waveform, and will be more intuitive. The main design has waveform display interface, parameter setting interface, and check the interface, after run over it show result and save test data. Because of the standard transfcormer is a traditional electromagnetic transformer, its output is different from electronic transformer, the output is converted into the standard signal with a conversion device. Standard voltage signals using inductive voltage divider is rating of 0.005, standard current signal using no-inductance resistors is rating of 0.01, and last, convert it into an electronic transformer to compare the same standard output, Collecting device also can be choosen with low scale and more accurate capturing cards, the device uses NI PCI-6281 high-precision acquisition card NI PCI-6281, and PC can communicate better to shorten the development cycle. Direct comparison method is adopted in this paper, The two signals must be collected in a synchronized manner, Synchronization means which is based on ARM architecture STM32 have designed to meet the requirements, synchronization means is ARM architecture minimum system components synchronous triggering device, its change the mode of operation of the output pulse signal synchronous triggering electronic transformer and standard transformers for synchronous acquisition.Through test to the system and data analysis, the accuracy class of calibration device up to 0.05 or above. It is more accurate than electronic transformer with two levels, It can be used to verify the electronic transformer with level 0.2 or less.