Detection of Partial Discharges Occurring in Propulsion Coils of Superconducting Maglev Systems Using an On-Board Radio Interferometer System with a Vector-Antenna

Condition monitoring techniques for ground coils used in superconducting magnetic levitation (Maglev) systems are required. In this study, an on-board radio interferometer system with a vector-antenna was developed to locate partial discharge (PD) sources occurring in propulsion coils of superconducting Maglev systems and to know the propagation characteristics of electromagnetic (EM) waves emitted from PD sources. PD current generally develops into multiple directions, that is, the EM waves emitted from the PD current have also multidirectional components. The structures and the arrangement of propulsion coils and levitation-guidance coils might influence the propagation of EM waves. The vector-antenna composed of vertical and horizontal dipole-antennas was set to the center of the antenna-array of the on-board radio interferometer system. Three sets of mock-ups of the propulsion coil and the levitation-guidance coil were also developed in order to evaluate easily the on-board radio interferometer system. One of the propulsion coils has eight cylinder-shaped holes penetrating through the insulating material to the inner conductor for attaching a cap with a needle-electrode; one or some of the holes can be voluntarily chosen. PD current was generated in an air-gap between the tip of the needle-electrode and the surface of the inner conductor. Experimental results show that a PD source generated at a voluntary position of the propulsion coil could be located by using the on-board radio interferometer system; the vertical and horizontal components (electric fields) of the EM waves emitted from the PD source could be separately received by using the vector-antenna.