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
