A research report submitted to the Faculty of Engineering and the
Built Environment, University of the Witwatersrand, in ful lment
of the requirements for the degree of Master of Science in
Engineering.
June 2016 / It has been reported in literature that newly installed cable accessories can pass
typical commissioning tests and yet show signi cant PD activity leading to premature
failure in the long term. This research report details the partial discharge (PD)
characterisation of three arti cial defects in MV cable terminations, at both power
and very low frequency (VLF). The defects included a semi-conductor feather, a
tram line in the cross-linked polyethylene (XLPE) insulation and an XLPE ring
cut. The experimental methodology involved subjecting the terminations to a
standard overvoltage withstand test, after which the PD activity was monitored,
at 0.1 Hz and at 50 Hz excitation frequencies. All the defects passed the overvoltage
test, despite some showing signi cant discharges. The defects gave distinct
phase-resolved PD patterns that are e ectively invariant of excitation frequency.
The PD magnitudes at power frequency were typically bigger than at VLF, while
the PD inception voltages tended to be lower at VLF. The PD magnitudes of
the semi-conductor feather defect surface discharges were found to increase with
increasing applied voltage, while no increase was observed for the tram line and
ring cut void discharges. The results show that common installation defects in MV
cable terminations can be suitably characterised using VLF PD measurements / MT2016
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21149 |
| Date | 11 October 2016 |
| Creators | Fynes-Clinton, Daniel |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf, application/pdf |
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