Abstract
Insulation degradation is an irreversible phenomenon that can potentially lead to failure of power cable systems. This paper describes the results of an experimental investigation into the influence of direct current (DC) superimposed with harmonic voltages on both partial discharge (PD) activity and electrical tree (ET) phenomena within polymeric insulations. The test samples were prepared from a high voltage direct current (HVDC) cross linked polyethylene (XLPE) power cable. A double electrode arrangement was employed to produce divergent electric fields within the test samples that could possibly result in formation of electrical trees. The developed ETs were observed via an optical method and, at the same time, the emanating PD pulses were measured using conventional techniques. The results show a tenable relation between ETs, PD activities, and the level of harmonic voltages. An increase in harmonic levels has a marked effect on development of electrical trees as the firing angle increases, which also leads to higher activity of partial discharges. This study of the influencing operational parameters of HVDC converters on power cable insulation is predicted to contribute to enhancements in cable design and progressive advancement in condition monitoring and insulation diagnostic techniques that can lead to more effective asset management in HVDC systems.
Highlights
High Voltage Direct Current (DC) (HVDC) power cables are some of the main components of power transmission in offshore renewable integrations, cross-country interconnections and High Voltage DC (HVDC) grids [1]
This study aims to address the influence of HVDC voltages superimposed with characteristic harmonics on electrical tree developments and partial discharge behavior within HVDC XLPE cable insulation
The influence of DC voltages superimposed with characteristic harmonics on partial discharge (PD) activity and electrical treeing (ET)
Summary
High Voltage DC (HVDC) power cables are some of the main components of power transmission in offshore renewable integrations, cross-country interconnections and HVDC grids [1]. Under such HVDC schemes, as opposed to line commutated converter (LCC). XLPE power cables would not experience polarity reversal in VSC HVDC systems. Employment of environmentally friendly power cables and the technological advancements in terms of cable design, material, and manufacturing technologies are amongst the incentives to adopt polymeric cables in HVDC power transmission. Such cables can potentially operate in LCC schemes as well, where transmission of large amount of power is feasible [2,3]
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