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- 2014 (27) (entfernen)
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- Fibre-optic sensor (1)
- Fibre-optic strain sensor (1)
- High voltage cable accessories (1)
Eingeladener Vortrag
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Fibre-optic sensors need to be more established in the sensor market. Their advantages have unquestionably been verified by numerous demonstrations. However, there are some open questions leading now and then to restraints in the user's community. The paper dicusses examples where fibre-optic sensors provide outstanding knowledge about the structure's behaviour, but application is often challenging. Requirements are listed and open questions to be solved are discussed. Short outlook to standards useful for better design, characterization and application is given. Standards are the basis for establiching SHM systems, especially for safety-critical structural diagnostics.
Movements in geological areas are mostly concentrated on faults or slipping zones. Detection of movements reaching critical values is of crucial importance to avoid losses and harms. The paper presents a new technology of detecting deformations and movements in soil or rock massifs. The core part of the sensing system is a tiny rod with embedded optical sensor fibres. This deformation measurement system was developed and the sensing rod can be installed in a borehole and enables the detection of beginning soil movements. The amount of deformation in soil or rock formations can then be estimated. The sensing rod has an outer diameter of 3 mm to 6 mm and contains several optical fibres. One fibre is used as online measurement system and provides integral strain information along the whole length of the rod. In case of a safety-relevant deformation (warning signal), the second sensing system based on fibre Bragg grating sensors positioned close to the expected shear zone will be activated and records then resulting deformations in detail.
Modern optical partial discharge (PD) detection system based on fiber-optic sensors for PD on-line health monitoring in high-voltage (HV) cable terminations necessarily requires optically transparent or translucent insulation materials. The optically compatible silicone rubbers are the key to facilitate such innovative technology. In this work, AC 50 Hz dielectric strength Eb and mechanical properties of three types of commercially available silicone rubbers have been investigated. The investigations revealed that the translucent silicone rubber has a good mechanical performance but its Eb value is considered too low. However it is sufficiently good for use as base material for rubber stress cones. Unfortunately, its optical transmittance is poor compared to optically clear transparent silicones. On the other hand, the mechanical properties of transparent silicone rubbers do not comply with those demanded from push-on stress cones. In particular, their elongation at break is considered too low for that application. However they provide the Eb values of about 28 kV/mm to 29 kV/mm at 0.5 mm thickness, which are higher than those of the translucent type. Moreover, it was found that the post-curing process does not provide a positive impact on the ultimate elongation of silicone rubbers.