Open AccessCorona at Large Coated Electrodes
Author(s) -
Mats Larsson,
Olof Hjortstam,
Håkan Faleke,
Liliana Arévalo,
Wei Dong,
Ming Li
Publication year - 2018
Publication title -
proceedings of the nordic insulation symposium
Language(s) - English
Resource type - Journals
ISSN - 2535-3969
DOI - 10.5324/nordis.v0i23.2469
Subject(s) - electrode , corona discharge , electric field , materials science , corona (planetary geology) , coating , composite material , layer (electronics) , corona ring , voltage , high voltage , polarity (international relations) , polarity reversal , optoelectronics , electrical engineering , chemistry , physics , quantum mechanics , astrobiology , venus , engineering , biochemistry , cell
In geometries relevant form HVDC applications where large electrodes and large air gaps are utilized, the observed corona can be quite different from geometries studied in the literature where needles or wires are used as high voltage electrodes. Corona discharges at large electrodes often initiates when the electric field on the electrode surface appears lower than the critical electric field strength, 2.4 kV/mm. Surface contamination of the electrode has been pointed out as the reason for such discharge events. Our experimental results indicate that one possible way to prevent such corona is to coat the electrode with an insulating material, such as epoxy or oxide layers. It seems that the layer separates any corona inducing particle from the electrode, which in turn hinders the corona to form. However, as the layer breaks down and gets punctured, the corona preventing propertied disappears and corona forms easily. We conclude that as long as the layer doesn’t get punctured, coating electrodes with insulating material is preventing corona to initiate at electrical fields below the critical electric field, as given by the electrode geometry. In contrast to positive polarity, for negative polarity the epoxy coating could withstand high electric fields without breaking down.