Accuracy of Instrument Voltage Transformers - Background Information and a New Model-Based Approach of Verifying the Transformer Accuracy

摘要

The performance of instrument voltage transformers is essential for a reliable and safe power supply. Without accurate devices that fulfil the specified technical requirements, malfunctions or economical disadvantages may occur. Against this background, the first part of this paper gives an overview of the requirements of instrument voltage transformers regarding metering and protection purposes. Next to some technical basics, the differences between the IEC and IEEE standards are highlighted. The main part of this paper concentrates on the accuracy of instrument voltage transformers. The theoretical background behind the transformer error and methods of verifying the accuracy class are discussed. A newly developed method to be able to calibrate instrument voltage transformers is proposed. This method uses a modeling approach to determine the transformers accuracy. Due to the mobile character of this new approach, it is designated to be used for on-site calibration as well as for laboratory calibration of voltage transformers.