Electrical Tree Initiation and Growth in LDPE Under Negative HVDC Superimposed With AC Ripples

Liu, Fang, Rowland, Simon, Zheng, Hualong, Peesapati, Vidyadhar and Behnsen, Julia ORCID: 0000-0003-1511-3051 (2022) Electrical Tree Initiation and Growth in LDPE Under Negative HVDC Superimposed With AC Ripples. IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, 29 (6). pp. 2147-2154.

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Official URL: http://dx.doi.org/10.1109/tdei.2022.3212965

Abstract

Understanding the role of power quality in the aging of HVdc cable systems is critical to the reliable connection of offshore renewable energy sources, and hence global ambitions to reduce carbon emissions. This work investigates electrical treeing with a needle-plane geometry in low-density polyethylene (LDPE) under a high negative dc voltage superimposed with ac ripples (-60 kV dc ± 7 kV ac). Tree initiation showed behavior similar to that widely reported under pure power frequencies. Subsequent tree growth, however, was observed to be confined in a smaller area with limited length and width than seen under pure ac voltages, even after long periods of voltage application. Traditional 2-D imaging showed overlapped tree channels which developed to cover the whole area within the tree outline. A distinguishing tree shape resulted, which we have named a 'slim bouquet' shape. The volume rendering from X-ray computed tomography (XCT) showed the structure had a 3-D fractal dimension greater than 2, considerably larger than its 2-D representation. PD signals during the growth had wing-like phase-resolved partial discharge (PRPD) clusters and signal phase concentrations between 10°-45° appeared after hours of growth. There was a comb-like appearance in maximum partial discharge (PD) magnitude variation, which is typical in pure high negative dc fields. Consideration is given to both space charge distribution controlled by high dc fields and continuous degradation by ac fields to explain the slim bouquet tree formation.

Item Type:	Article
Uncontrolled Keywords:	3-D imaging, ac ripples, electrical trees, HVdc, partial discharge (PD), slim bouquet, space charge
Divisions:	Faculty of Science and Engineering > School of Engineering
Depositing User:	Symplectic Admin
Date Deposited:	14 Mar 2023 16:41
Last Modified:	15 Mar 2024 18:09
DOI:	10.1109/TDEI.2022.3212965
Open Access URL:	https://research.manchester.ac.uk/en/publications/...
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3169078