Condition monitoring of current transformers using frequency domain dielectric spectroscopy

This paper presents the possibility of using Frequency Domain Dielectric Spectroscopy (FDS) measurement as a condition monitoring tool for Current Transformers (CT). A 132 kV live tank type CT was thermally aged in the laboratory for 840 hours by injecting twice the rated current from the CT's secondary side. The FDS responses were periodically measured and modeled using dielectric response functions in the frequency domain. In parallel, FDS responses were obtained on nine 132 kV field-aged CTs (live tank and dead tank). The FDS responses were modeled and compared with the laboratory-aged results. It was found that some of the field-aged CTs showed similar FDS responses as laboratory-aged CT sample.