Instrument transformers for medium- and high-voltage applications play a key role in energy supply. Acting as the link between the primary network and the metering or protection equipment connected to the secondary side, a safe and reliable operation without failures is essential. In relation to this background, this paper discusses testing and diagnostic methods for instrument transformers. Different application examples are presented that help to ensure an efficient production process at the manufacturing site and efficient on-site testing for site acceptance, commissioning or regular maintenance.
Keywords: calibration, commissioning, diagnostics, instrument transformer, testing
The importance of the testing and diagnostics of instrument transformers (transformers used for protection and measuring purposes) is all too often underestimated. Although the cost of instrument transformers (ITs) is relatively low, their correct and uninterrupted operation is an essential prerequisite for good operational management and a reliable supply of energy. ITs are precise measuring instruments that have to satisfy the most stringent demands in terms of operating range and insulation. Incorrect operation, the use of defective ITs, or the failure of an installed IT can have far-reaching financial, as well as technical, consequences . In addition to these operational aspects, manufacturers endeavor to produce high-quality equipment at a reasonable cost. Carrying out the correct tests during the production process will not only save time, but also improve the quality of the final product .
Current and voltage transformers are normally single-phase transformers, which, despite their differences in design, can essentially be described using the familiar transformer equivalent circuit diagram.
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