Development of a new detection method of partial discharge for EHV long‐distance active cable line

A new method was used to measure the characteristics of partial discharge (PD) for an active 9.5‐km long‐distance 275‐kV XLPE cable line with insulating joints. It was found that the detection of PD and the calibration of detection sensitivity were carried out safely and easily. The proposed method includes: detection of PDs and injection of calibration pulses using two pairs of metal electrodes placed on PVC jackets with anti‐corrosion layers separated by a joint sleeve sectionalizing insulator; measurement of detection sensitivity with distance using calibration pulses injected from an adjacent insulating joint; detection of PDs with a high S/N ratio measured at a frequency corresponding to the lowest noise level; and usage of rf cores attached at cross‐bonding leads and wires for sheath current limiters to reduce the crosstalk of signal and noise through these lines at insulating joints. Using a combination of these techniques, the highest detection sensitivity was 1 pC in the vicinity of an insulating joint, and 15 pC at 617 m from the adjacent joint. The sensitivity obtained by the conventional PD measurement using a low‐frequency method was at most 1000 pC.