Aging of Oil-Impregnated Paper High Voltage Current Transformers: Long Duration Test and Lifespan Estimation

Although the current transformer (CT) is an essential component in the electrical power system and its failure may result in serious consequences, there are no accelerated aging tests for this equipment prescribed by technical standards. Life estimation for this equipment is generally made based on field experience, something that cannot be done for new models and/or new manufacturers. In this work, experimental results of life tests performed on mockups, representing high-voltage CTs with oil-impregnated paper insulation, are presented and discussed. The analysis is based on the application of a multistress model, which combines the Montsinger rule and inverse power law. The proposed approach considers the existence of threshold values for electrical and thermal stresses, below them, electrical and thermal degradation is negligible. An order of magnitude for the electrical stress threshold value (
${E}_{{0}}$
) and for the electrical aging exponent (
${n}$
) is obtained from the application of the test results to the model used in this investigation.