A microfluidic system combined with substrate-integrated hollow waveguide (iHWG) vapor phase infrared spectroscopy has been developed for evaluating the chemical activity of volatile compounds dissolved in complex fluids. Chemical activity is an important yet rarely exploited parameter in process analysis and control. Access to chemical activity parameters enables systematic studies on phase diagrams of complex fluids, the detection of aggregation processes, etc. The instrumental approach developed herein uniquely enables controlled evaporation/permeation from a sample solution into a hollow waveguide structure and the analysis of the partial pressures of volatile constituents. For the example of a binary system, it was shown that the chemical activity may be deduced from partial pressure measurements at thermodynamic equilibrium conditions. The combined microfluidic-iHWG midinfrared sensor system (μFLUID-IR) allows the realization of such studies in the absence of any perturbations provoked by sampling operations, which is unavoidable using state-of-the-art analytical techniques such as headspace gas chromatography. For demonstration purposes, a water/ethanol mixture was investigated, and the derived data was cross-validated with established literature values at different mixture ratios. Next to perturbation-free measurements, a response time of the sensor <150 s ( t) at a recovery time <300 s ( t) has been achieved, which substantiates the utility of μFLUID-IR for future process analysis-and-control applications.

A sustained current conduction in the breaking chamber after a current interruption has been observed. This current, which we named 'Post-recovery (PR) current', is in phase with the applied voltage and its value ranges from several milliamps up to several amps. The present study shows that the probable origin of the PR current is an ionic conduction of SF6 between the contacts. The estimated temperature of the conducting gas is about approximately 2000 K. The evolution of the temperature is in good accordance with a computational model based on the resolution of two-dimensional Navier-Stokes equations.

A novel post-arc current measuring shunt is described. This shunt employs parrallel connected diodes to automaticaly insert and disconnect the measurement resistance, very close to the current zero.-The realized precision and sensitivity allow reproductible measurements down to tens of milliamperes range, with about a 5 MHz bandwidth. Furthermore repetitive testing with main currents of up to 80 kA peak poses no problem with this configuration.Using this technique we have discovered a new type of post-arc current which can last many milliseconds without provoking circuit breaker failure. We call this the "post-recovery current".

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This paper considers the research design and development of an essentially new type of SF6 circuit-breaker. The design uses the principle of "autoexpansion" a combination of rotary arc and self pressurisation principles. The paper discusses the operating principles and the design considerations involved in this interruption technique. In addition the principle performance features are given, particulary in comparison with existing SF6 techniques. Finally details are given of the research techniques and diagnostic systems that have facilitated the design and development of this circuit-breaker.