The University of Southampton
University of Southampton Institutional Repository

The influence of AC and DC voltages on electrical treeing in low density polyethylene

The influence of AC and DC voltages on electrical treeing in low density polyethylene
The influence of AC and DC voltages on electrical treeing in low density polyethylene
Electrical tree growth is a well-documented process leading to failure of high voltage polymeric insulation under AC stresses. However, tree growth in HVDC insulation failure is not well understood. This work considers electrical tree degradation in polymeric insulation subjected to combined AC and DC voltages. Tests in LDPE samples of needle-plane geometry yield three types of electrical trees, which grow depending on the magnitude of the AC components, irrespective of the DC voltages. In tests with an AC component of 10 kV (peak amplitude), 12 kV and 15 kV trees are distinguished by both the conductivity of tree channels and the tree shape, and are referred to as either conducting trees, non-conducting branch trees or non-conducting bush trees respectively. With 10 kV AC, tree initiation was significantly accelerated by superimposing -20 kV DC. With +20 kV DC, the incepted trees had more bifurcations, but there was no major change to tree initiation time. Space charge measurements on thin LDPE films provide a basis for understanding the difference between tree initiation with +DC and –DC voltages. The subsequent propagation of conducting trees were not influenced by biasing the 10 kV AC. With 12 kV AC and 15 kV AC, the growths of non-conducting branch and bush trees were both accelerated by positive biasing. A retardation was observed in bush tree growth with -15 kV DC. The effects of DC voltage polarity on tree morphology are different for branch and bush trees. Different relationships between PD magnitudes and tree growth were also found between branch and bush trees. The tree length determined PD magnitudes in branch trees and the evolution of PD in bush trees suggest that the additional DC stress has no impact to PD magnitudes. Nevertheless, DC bias effects on the symmetry between positive and negative discharges have been evidenced through PD analysis for bush trees. Moreover, the modifications on the shape of bush trees are believed to be associated with the changes in PD asymmetry. This work has illustrated the importance of AC ripples in the failure mechanisms in HVDC insulation.
DC power quality, Electrical tree, Partial discharge, Polarity dependence
0142-0615
Chen, Guanghui
3de45a9c-6c9a-4bcb-90c3-d7e26be21819
Zheng, Hualong
27bc341c-4743-4114-87c0-1f0b184e752f
Rowland, S
01777146-a7a7-458d-acc0-3d68701bf434
Chen, Guanghui
3de45a9c-6c9a-4bcb-90c3-d7e26be21819
Zheng, Hualong
27bc341c-4743-4114-87c0-1f0b184e752f
Rowland, S
01777146-a7a7-458d-acc0-3d68701bf434

Chen, Guanghui, Zheng, Hualong and Rowland, S (2020) The influence of AC and DC voltages on electrical treeing in low density polyethylene. International Journal of Electrical Power & Energy Systems, 114, [105386]. (doi:10.1016/j.ijepes.2019.105386).

Record type: Article

Abstract

Electrical tree growth is a well-documented process leading to failure of high voltage polymeric insulation under AC stresses. However, tree growth in HVDC insulation failure is not well understood. This work considers electrical tree degradation in polymeric insulation subjected to combined AC and DC voltages. Tests in LDPE samples of needle-plane geometry yield three types of electrical trees, which grow depending on the magnitude of the AC components, irrespective of the DC voltages. In tests with an AC component of 10 kV (peak amplitude), 12 kV and 15 kV trees are distinguished by both the conductivity of tree channels and the tree shape, and are referred to as either conducting trees, non-conducting branch trees or non-conducting bush trees respectively. With 10 kV AC, tree initiation was significantly accelerated by superimposing -20 kV DC. With +20 kV DC, the incepted trees had more bifurcations, but there was no major change to tree initiation time. Space charge measurements on thin LDPE films provide a basis for understanding the difference between tree initiation with +DC and –DC voltages. The subsequent propagation of conducting trees were not influenced by biasing the 10 kV AC. With 12 kV AC and 15 kV AC, the growths of non-conducting branch and bush trees were both accelerated by positive biasing. A retardation was observed in bush tree growth with -15 kV DC. The effects of DC voltage polarity on tree morphology are different for branch and bush trees. Different relationships between PD magnitudes and tree growth were also found between branch and bush trees. The tree length determined PD magnitudes in branch trees and the evolution of PD in bush trees suggest that the additional DC stress has no impact to PD magnitudes. Nevertheless, DC bias effects on the symmetry between positive and negative discharges have been evidenced through PD analysis for bush trees. Moreover, the modifications on the shape of bush trees are believed to be associated with the changes in PD asymmetry. This work has illustrated the importance of AC ripples in the failure mechanisms in HVDC insulation.

Text
Hualong_UoM_Electrical Power and Energy Systems - Version of Record
Available under License Creative Commons Attribution.
Download (4kB)
Text
ACDC JEPE Revised
Download (4kB)

More information

Accepted/In Press date: 24 June 2019
e-pub ahead of print date: 13 July 2019
Published date: January 2020
Keywords: DC power quality, Electrical tree, Partial discharge, Polarity dependence

Identifiers

Local EPrints ID: 432647
URI: http://eprints.soton.ac.uk/id/eprint/432647
ISSN: 0142-0615
PURE UUID: 14e0a9af-814d-45e0-971d-797c463c4cce

Catalogue record

Date deposited: 23 Jul 2019 16:30
Last modified: 14 Sep 2021 18:41

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×