Time Development of Voltage Frequency Dependence of Partial Discharge Activity in Voids
DOI:
https://doi.org/10.5324/nordis.v0i26.3294Abstract
Condition assessment of high voltage equipment based on partial discharge measurements is often performed after a voltage pre-conditioning period. The aim of this paper is to present results from experimental examinations of time variance of partial discharge activity and to propose physical explanations of the phenomena observed. Experiments were performed on laboratory made 3 mm thick discs of generator bar insulation, consisting of mica and glass fiber reinforced epoxy with a 0.5 mm thick cylindrical void surfaces of 10 mm in diameter. The effect of conducting and insulating void surfaces was examined using copper tape as upper and lower electrodes of the voids. All objects were tested by 12 one-minute long AC voltage frequency sweeps at frequencies from 50 Hz to 0.1 Hz distributed in time from start of the experiment, after initial one-hour constant 50 Hz voltage application and during object short-circuiting for 20 h. The main result shows that in case of insulating voids the apparent charges vanished after the one-hour constant 50 Hz voltage application. After a grounding period of 5 minutes, the charge magnitudes slowly increased with time until reaching steady state after about 4-8 hours. Test objects with conductive void surfaces showed such reduction in case of PD testing at 0.1 Hz only. At voltage frequencies above 10 Hz the measured PD magnitudes were found to be nearly constant, close to the expected high theoretical value. This indicate that PD by-products strongly affected the void resistivity and thereby affect the PD activity of insulating voids. These by-products are temporary and disappear with time.
Nedladdningar
##submission.downloads##
Publicerad
Nummer
Sektion
Licens
Proceedings of the Nordic Insulation Symposium licenses all content of the journal under a Creative Commons Attribution (CC-BY) licence. This means, among other things, that anyone is free to copy and distribute the content, as long as they give proper credit to the author(s) and the journal. For further information, see Creative Commons website for human readable or lawyer readable versions.
Authors who publish with this journal agree to the following terms:
1. Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
2. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
3. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).