High resolution locating of normal transitions in a high temperature superconducting coil by capacitor type voltage terminals

It is important to locate positions of normal transitions in a high temperature superconducting coil for identifying its design and fabrication weakness. The authors have proposed capacitor type voltage terminals as a contactless method to measure voltages of the coil windings through insulation of the windings. This method was useful for locating the positions of the normal transitions. Higher resolution of the location is achieved by attaching many terminals to the coil. Then shorter electro-conductive sheets of capacitor type voltage terminals are needed. However, the shorter sheets make the measured voltage signals small and the signals are supposed to be incorrectly measured. In this paper, the authors propose a method to achieve high resolution locating by long electro-conductive sheets of capacitor type voltage terminals. Numerical values of the measured voltage by the terminals depend on the positions of the normal transitions and therefore analysis of the values can achieve high resolution locating without increasing the number of the terminals. Through experimental results for a Bi2223 HTS coil, it was confirmed that the proposed method could achieve the high resolution locating.