Thesis
Gas-solid interfaces stressed with HV impulses : surface flashover behaviour and control
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2023
- Thesis identifier
- T16718
- Person Identifier (Local)
- 201779883
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- In pulsed power engineering, solid spacers are used to insulate high voltage parts from extraneous metal parts, providing electrical insulation as well as mechanical support. The breakdown/flashover voltage, at which a discharge process initiates across the gas-solid interface, is important in the design process, as it informs designers of specific threshold ‘failure’ voltages of the insulation system. In this thesis, a method to potentially increase the failure voltage, tested under multiple environmental conditions, without increasing the length of the solid spacer, was investigated. Three dielectric materials: High-Density Polyethylene (HDPE), Polyetherimide (Ultem) and Polyoxymethylene (Delrin), were tested under 100/700 ns impulse voltages. Cylindrical spacers made of these materials were located in the centre of a plane-parallel electrode arrangement in air, which provided a quasi-uniform field distribution. Breakdown and flashover tests were performed in a sealed container at air pressures of −0.5, 0 and 0.5 bar gauge, with varying relative humidity (RH) level of <10%, ~50% and >90%. The materials were tested under both, negative and positive, polarity impulses. Additionally, the surfaces of a set of solid spacers were subjected to a ‘knurled’ finish, where ~0.5 mm indentations are added to the surface of the materials, prior to testing, to allow comparison with the breakdown voltages for samples with ‘smooth’ (machined) surface finishes. The results show that the flashover voltage is controlled by the physical insulation system and environmental parameters, where the multiple test conditions yielded results where the V50 breakdown voltage for samples with a smooth surface finish was higher than for knurled, by up to ~55 kV; where there were similar V50 breakdown voltages for each type of surface finish; and where the knurled spacer resulted in a higher (by up to ~66 kV) hold-off voltage than the corresponding smooth spacer. Each of these results is discussed herein, particularly in terms of the location of the discharge channel at breakdown, where changing the physical and environmental test parameters was shown to affect the discharge path, and therefore the flashover voltage of the insulation system. The results and discussion will inform designers and operators of outdoor pulsed power systems on the design of air-solid insulation systems, and the control of the flashover characteristics, under varying environmental conditions.
- Advisor / supervisor
- Timoshkin, Igor
- Wilson, Mark
- Resource Type
- DOI
Relazioni
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PDF of thesis T16718 | 2023-10-30 | Pubblico | Scaricare |