Detection of Local Abnormalities in Windings of High-Temperature Superconducting Transformers by Using Pick-Up Coils

We have proposed a new method for monitoring the condition in windings of high-temperature superconducting transformers during operation. In this method, pick-up coil pairs arranged outside the cryostat for measuring electric fields and magnetic fields are used. This indirect method has benefits such as high reliability, safe detection, and easy maintenance. The purpose of this paper is to confirm experimentally whether the system using pick-up coil pairs can detect unusual local conditions in the windings of high-temperature superconducting transformers. For the purpose of this paper, a test transformer of 800 VA class, which was wound with Bi-2223 multifilamentary tapes, was fabricated. The transformer was monitored by our system. When a local temperature rise in the primary winding of the transformer in liquid nitrogen was generated, the monitoring test of the transformer by our system was carried out, which confirmed that our system could detect the local abnormalities in windings of the transformer during operation.