Measurement of Temperature Gradients Inside a Medium Voltage Current Transformer

Current transformers are series devices used in power systems for measurement and protection purposes. Useful operational life of these devices is largely determined by the highest temperature seen by them during various loading conditions. In this paper, we describe a unique experimental setup designed to measure top-oil as well as hot-spot temperature profiles of a medium voltage current transformer. Several thermocouples and fiber optic sensors were embedded in the core and winding of the current transformer. Temperatures could be measured at externally applied currents with an accuracy of plusmn 2 degC. Such temperature profiles are very useful for thermal modeling that eventually leads to life prediction of a transformer.