| Author: | Yeung, Kwong-tung Tony |
| Title: | Fibre-optic acoustic sensing of the presence and location of partial discharges in a high-voltage power transformer |
| Degree: | M.Sc. |
| Year: | 1997 |
| Subject: | Electric transformers Electric discharges Hong Kong Polytechnic University -- Dissertations |
| Department: | Multi-disciplinary Studies |
| Pages: | v, 75 leaves : ill. ; 30 cm |
| Language: | English |
| Abstract: | It has long been recognised that the level of partial discharge inside an oil-filled power transformer is a direct indication of the integrity of the insulation system. An acoustic detection method using externally mounted piezoelectric sensors for detecting partial discharges inside a power transformer has been introduced by E.Howells et. al. in the early 80's. The advantages and limitations of these detection systems were critically reviewed in this study. To overcome the inherent limitations of these systems, an all-fibre acoustic detection system using a Mach-Zehnder interferometer was introduced. This system , with its sensor installed inside the transformer tank, works on the principle that the acoustic pressure wave generated by the partial discharge when impinging on the fibre will change the refractive index of the fibre. This change in refractive index will in turn change the phase of the light emerging from the fibre. By detecting this phase change through the Mach-Zehnder interferometer and the demodulation circuit, the level of acoustic pressure and hence the level of partial discharge could be deduced. A detailed mathematical derivation of the pressure-phase change relationship was presented in this study. The mathematical models of the detection system and the demodulation circuit were also derived. Apart form detection, the discharge site could also be located by this system if more than three sensors were installed. By measuring the time of the acoustic pressure surge reaching these sensors, the discharge site could then be located by using the triangulation technique. In addition to the theoretical discussion, some practical considerations which arise when applying this detection system to real life situations were also discussed. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| b13986351.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 2.46 MB | Adobe PDF | View/Open |
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