Automatic Insulation Diagnosis Using the Characteristics of Electromagnetic Waves Due to Partial Discharges Occurring in Propulsion Coils

Safety operation of superconducting magnetic levitation (SC Maglev) systems needs automatic insulation diagnosis for a large number of propulsion coils and levitationguidance coils, which are arranged on both sidewalls of U-shaped guideways. Two sets of an on-board radio interferometer system with a vector-antenna were newly developed in order to detect PDs simultaneously for both sidewalls of U-shaped guideways. In this study, the two on-board radio interferometer systems with the vector-antennas were used to detect PDs generated in a cylindershaped void composed of a cylinder-shaped electrode and a plane electrode, which was set in a mock-up of propulsion coil. The cylinder-shaped electrodes with different diameters: <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.5 ~\text{mm}, 2$</tex> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{mm}, 4 ~\text{mm}, 6 ~\text{mm}, 8 ~\text{mm}$</tex>, and 10 mm were used; the gap length between the cylinder-shaped electrode and the plane electrode was set to 3 mm. Apparent charges, currents, and electromagnetic (EM) waves of PDs generated in the mock-up of propulsion coil were simultaneously measured by using a commercial PD measuring system based on the IEC60270 standard, a commercial current probe, and the two on-board radio interferometer systems with the vector-antennas, respectively. This paper describes the characteristics of the EM waves received by using the on-board radio interferometer systems with vector-antennas in order to use them for automatic insulation diagnosis.