Static Headspace GC/MS Method for Determination of Methanol and Ethanol Contents,as the Degradation Markers of Solid Insulation Systems of Power Transformers

Methanol in insulating oil has been proposed as a new marker for condition assessment of the solid insulation system of power transformers. In the current work, as a first step of using the new marker, an analytical static headspace gas chromatography/mass spectrometry method has been developed, optimized, and validated to measure methanol and ethanol contents in the insulating mineral oil. The analyzing setup consists of a 6890 N gas chromatograph equipped with a 5973 network mass spectrometer (MS) in the absence of a costly headspace autosampler, and the chromatography separation was performed on a 60 m × 320 µm × 0.5 µm VF-WAXms GC column. Calibration curves have been provided using several concentrations of the alcohols, and also limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation percentage (RSD%) have been determined.     

Strength measurements of silica optical fibers under severe environment

Optical fibers are key components in telecommunication technologies. Apart from optical specifications, optical fibers are expected to keep most of their physical properties for 10–20 years in current operating conditions. The reliability and the expected lifetime of optical links are closely related to action of the chemical environment on the silica network. However, the coating also contributes largely to the mechanical properties of the fibers.The aim of this work was to study the strength and the mechanical behavior of the silica optical fibers in an acid environment and with a permanent deformation. A container with ammonium bifluoride acid salt was plunged into hot water at different temperatures (55 and 75 °C). This emitted acid vapors which attacked the optical fibers for a period of 1–18 days. An aging study was performed on silica optical fibers with standard polyacrylate coating and with hermetic carbon coating. A dynamic two-point bending bench at different faceplate velocities (100, 200, 400 and 800 μm/s) was used. For comparison, the same dynamic measurements were also carried out on non-aged fibers.After acid vapor condensation, salt crystal deposits on the fibers were displayed using an electron scanning microscope. These crystals became visible to the naked eye from the seventh day.     

BOOK REVIEWS

Book reviewed in this article: Möbius and His Band: Mathematics and Astronomy in Nineteenth-Century Germany, John Fauvel, Raymond Flood, Robin Wilson A Practical Approach to Using Learning Styles in Math Instruction Ruby Bostick Midkiff and Rebecca Davis Thomasson Contextual Reality, Tower Chen Classroom Dynamics: Implementing a Technology-Based Learning Environment, Ellen B. Mandinach and Hugh F. Cline (Educational Testing Service)