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Low-tilt PV systems are increasingly common on flat roofs, where they enable a high power density. Yet there little is known about their requirements in terms of operations and maintenance, especially soiling. Here we present a case study on a 410 kWp system in Switzerland with a 5° tilt. Nineteen months of inverter data have been carefully analysed and correlated with consolidated weather data from four weather stations. Unlike systems on sloped roofs, which are deemed self-cleaning in Europe, this system demonstrates a clear and lasting benefit from active cleaning, with a 6% gain in energy yield.

The "Entreprises Electriques Fribourgeoises" (EEF), a Swiss utility, operate their medium voltage system with isolated neutral. In order to comply with the legal requirements for the security of people, the protection relays trip the lines also in the event of an earth fault. This kind of operation is not appreciated by our customers who have to accept too frequent interruptions of supply, mainly due to faults on the overhead lines. A recent study suggests using a shunt circuit-breaker in the HV/MV substations combined with the existing isolated neutral system. The improvement aimed at is to operate continuously our electrical network in case of an earth fault. Our studies show a potential reduction of supply interruptions of over 50 %. The solution with isolated neutral and a shunt circuit-breaker, consisting in grounding the earth- faulted phase to the ground at the HV/MV substation, seems to have all the advantages of a compensated neutral point (Petersen coil) as well as a lower cost (approx. ratio 1:4).

X-rays of all while and mixed-race men employed in crocidolite and amosite mines and mills were read independently by three experienced readers according to the ILO U/C classification. Abnormality was regarded as present if reported by two or more readers. Parenchymal abnormality, defined as the presence of small irregular opacities of profusion 1/0 or greater, was found in 7.3% of the workers. Pleural thickening was found in 4.5% of the workers, costophrenic angle obliteration in 3.2%, and pleural calcification in 1.7%. The prevalences of both pleural and parenchymal abnormality were strongly related to the duration of exposure to asbestos at work. The overall prevalence of abnormality increase from 4.0% in men with exposure for 1 year or less to 47.9% in men with more than 15 years of exposure. After taking into account the effects of age and duration of asbestos exposure, the prevalence of pleural abnormality was not predicted by fiber concentration. However, white men working with amosite tended to develop a higher prevalence of pleural abnormality than did those working with crocidolite. Compared to whites, men of mixed race, who only work with crocidolite, had a high prevalence of pleural abnormality in each exposure duration category. In contrast to pleural abnormality, the prevalence of parenchymal abnormality, after taking into account the effects of age and duration of exposure, was significantly predicted by fiber concentration but not by race or asbestos type. Our results suggest that parenchymal abnormality in workers in South African asbestos mines could be largely prevented by reducing exposure to fibers visible under the light microscope. However, this may not be the case for pleural abnormality.