The Method to Diagnose Local Abnormalities in Windings of High Temperature Superconducting Transformer During Load Changing

We propose a new monitoring system for high-temperature superconducting transformers. This system consists of pick-up coil pairs arranged outside the cryostat for measuring electric fields and magnetic fields. In a previous paper, it was confirmed that our system can detect the local abnormalities in a test transformer windings when its load doesn't change. In actual operation, however, the transformer load is always changing during practical operation. Therefore, the measured signal also changes with the load change even when abnormalities don't occur in the windings of the transformer. In this paper, we propose a method to cancel the change of the signal with the load change. In this method, our measuring signals are normalized by the power of a current. The purpose of this paper is to confirm that normalized signals don't change with the load change. Local abnormalities in the transformer windings were successfully detected and signal changes due to the changing load of the transformer were canceled. (C) 2016 The Authors. Published by Elsevier B.V.