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:
1
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;
2
measurement of detection sensitivity with distance using calibration pulses injected from an adjacent insulating joint;
3
detection of PDs with a high S/N ratio measured at a frequency corresponding to the lowest noise level; and
4
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.