Abstract
In practice, High-voltage (HV) cables are occasionally exposed to impulse and superimposed transient conditions, which may initiate partial discharges (PD) temporarily. Whether such PDs persist under AC voltage after the transient conditions have vanished, is at focus in the research described in this paper. Since for cross-linked polyethylene (XLPE) cables the accessories are weak links in the HV cable insulation system, we investigated the PD behavior of an artificial joint defect in a HV cable model under impulse and superimposed voltages. By applying a dedicated PD measuring system it was found that, the impulse and superimposed voltages can initiate PD in the artificial defect, which under local electrical field conditions can persist for some time. The different parameters of the applied voltages have different effects on the PD behavior.
Highlights
By facing the expanding power grids, underground power cables are installed more and more as an alternative to overhead lines [1,2]
Partial discharges were investigated in a 150 kV XLPE cable model under transient situations
An artificial defect was introduced in the cable joint in order to generate partial discharges
Summary
By facing the expanding power grids, underground power cables are installed more and more as an alternative to overhead lines [1,2]. More than half of the failure causes of XLPE cables in the sample pool (74%) occurred in the cable accessories due to installation related defects. The latter weak link of the insulation system is at focus in the present experimental investigation about transient effects. In the above-mentioned case defects may exist, in which PDs are not detectable in maintenance or commissioning tests, while these may initiate at abnormal superimposed voltage conditions. PD initiation in a XLPE cable system under impulse and superimposed voltages still lacks insight To address this our experiments are targeted to resolve the PD phenomena at the level of a laboratory cable model with an accessory defect, which becomes PD active under transient conditions.
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