Abstract
The health monitoring of superconducting fault current limiters (SFCL) is important for their large-scale exploitation in HVDC grids protection. The intrinsic non-homogeneity of critical current along the superconductor length can cause localized points of heating, called hotspots, in the SFCL device which can lead to device damage. In this paper we propose to use an extremely simple and cost-effective technique based on all-fibre Mach-Zehnder interferometers for hotspot detection in SFCLs, where the measurement arm of the interferometer is integrated with the SFCL and the reference arm remains in ambient. The system only consists of a laser, two optical fibre couplers and a photo detector. By studying the acquired interference patterns, even singular hotspots within the entire conductor length, can be informed in few milli-seconds, which is the fastest and most sensitive demonstration to the best of our knowledge that meets the SFCL requirement for fast hotspot detection.
Highlights
The grid is evolving as renewable energy generation is gradually taking more of a forefront in energy contribution
In this paper we propose to use an extremely simple and cost-effective technique based on all-fibre Mach-Zehnder interferometers for hotspot detection in superconducting fault current limiters (SFCL), where the measurement arm of the interferometer is integrated with the SFCL and the reference arm remains in ambient
A Akbar et al instantaneous strain-dominated response and enabling lower temperature hotspot detection, as summarized in Figure (6). This optical fibre sensing technique developed at EPFL for hotspot detection in SFCLs enables extremely fast hotspot detection
Summary
The grid is evolving as renewable energy generation is gradually taking more of a forefront in energy contribution. HVDC links connect offshore renewable energy generation to the distribution grid; with increasing renewable energy generation the grid will gradually transform into a meshed HVDC grid. The European Union project FastGrid aims at improving the REBCO tape archtitecture by increasing the limitation electric field with the overall goal of making a low length economically feasible SFCL device [6]. Since the research presented in this paper is carried out in the framework of the FastGrid project, emphasis is placed on a DC device for HVDC grids. It should be noted, that the hotspot detection technique for SFCLs outlined in this paper can be employed in many high temperature
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