Internal defect position evaluation of the ground coil by detecting the electromagnetic waves from the partial discharge

As a huge number of ground coils will be used outdoors for a long time in the superconducting magnetically levitated transportation (Maglev) system, a reduction in ground coil cost with high reliability will be required. Especially the propulsion coil needs the high insulation stability as the high-voltage equipment. On the other hand, as it is assumable that the ground coil has the resin molded winding coil with coreless construction, the ground coil must be exposed to the severe environment where it receives electromagnetic force directly. Therefore, there is a possibility that minute defects that are latent in the mold construction of the ground coil may expand, become apparent and cause of deterioration of the insulation stability. In this paper, we examined the insulation diagnostic measures to assess the existence/nonexistence of the inside defect and locate the defect position by setting a simulated defect artificially inside the mold construction of the ground coil and detecting the electromagnetic waves effectively that are generated from the discharge at the defect point.