Detection of Partial Discharges Occurring in Oil-Filled Cable Joints Arranged in a Mock-Up Tunnel Using a Radio Interferometer System

We have been developing a radio interferometer system to detect partial discharges (PD) occurring in joints of oil-filled (OF)-cables. In this study, the radio interferometer system was used to detect PDs generated in a pin hole of insulation papers set in a joint of 154 kV OF-cables and that of 275 kV OF-cables. It is planned that the measurement for PDs is conducted on the upper floor than the floor on which underground cables are arranged; therefore, the antenna-array of radio interferometer system was set behind a concrete wall with the width of 0.3 m placed in a mock-up tunnel. The mock-up tunnel, of which size is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2 \mathrm{m} \times 2 \mathrm{m} \times 6 \mathrm{m}$</tex>, was used for consideration of actual usage of the radio interferometer system. It was confirmed that the electromagnetic (EM) waves due to PDs leaking from the flange of OF-cable joint by using the radio interferometer system. The characteristics of the PD currents and EM waves are also described.