Localization of electrical insulation failures in superconducting collared coils by analysis of the distortion of a pulsed magnetic field

Abstract

The localization of possible electrical faults in superconducting accelerator magnets may, in most cases, be a complex, expensive and time-consuming process. In particular, inter-turn short circuits and failures of the ground insulation are well detectable when the magnet is collared, but often disappear after disassembly for repair due to the release of the pre-stress in the coils. The fault localization method presented in this paper is based on the measurement and analysis of the magnetic field generated inside the magnet aperture by a high voltage pulse. The presence of the fault modifies the distribution of the current in the coils and produces a distortion of the magnetic field. The described method aims at locating both the longitudinal and azimuthal position of the fault-affected area. The test method, the transient case FEM models and the implemented experimental set-up are presented and discussed for the LHC dipole models. Abstract The localization of possible electrical faults in superconducting accelerator magnets may, in most cases, be a complex, expensive and time-consuming process. In particular, inter-turn short circuits and failures of the ground insulation are well detectable when the magnet is collared, but often disappear after disassembly for repair due to the release of the pre-stress in the coils.The fault localization method presented in this paper is based on the measurement and analysis of the magnetic field generated inside the magnet aperture by a high voltage pulse. The presence of the fault modifies the distribution of the current in the coils and produces a distortion of the magnetic field. The described method aims at locating both the longitudinal and azimuthal position of the fault-affected area. The test method, the transient case FEM models and the implemented experimental set-up are presented and discussed for the LHC dipole models.

Errors in measurement of current distribution in a superconducting tape

“…The matter is of importance for the homogeneity of critical current density [7][8][9][10][11], loss dissipation [12,13], thermal stability [5] and defectoscopy in general [14], including medical applications [15,16].…”

Short Circuit Localization in the LHC Main Dipole Coils by Means of Room Temperature Magnetic Measurements

“…In this paper we present a method that has been developed to localize the short circuit using the magnetic field measurement at room temperature following the experience reported in [2][3]. Electrical shorts produce a field perturbation which is very large compared to the random part induced by tolerances of components and of assembly procedures.…”