When PQ problems become apparent – usually in the form of a disruption – they are usually referred to as ‘events’. This terminology is misleading because it hides the fact that the causes of many ‘event’ could have been identified in advance by the use of predictive maintenance techniques. This Application Note proposes that, rather than simply responding to problems, PQ should be continuously monitored as part of a planned maintenance activity.
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Flicker is the impression of unsteadiness of visual sensation induced by cyclic variation in the intensity or spectral content of a light source due to fluctuation of the supply voltage. It does not have any important effect on equipment, but it affects the concentration and productivity of people.Read full article
Unbalance can be caused by the presence of single-phase generators, such as photovoltaic units, unbalanced impedance of the distribution system, due to geometric effects, and unequal loading of the phases. Unbalance can have a serious effect on the performance and energy efficiency of three-phase equipment such as induction motors, transformers and electronic converters. In most circumstances, serious unbalance can be avoided by good installation practice, but some loads, such as railways, require special attention.
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This Application Note discusses the causes and effects of voltage dips. Some dips are caused within the installation by, for example, starting of heavy motors or other loads, and these are usually easy to identify and resolve. Most dips originate in the supply network as the result of faults and these can neither be predicted nor controlled by the user. The causes and characteristics of network dips are discussed.Read full article
RETScreen International is a unique decision support tool developed with the contribution of numerous experts from government, industry, and academia. Over the coming months, Leonardo ENERGY will be publishing a series of webcasts on energy project analysis using RETScreen.
RETScreen 4: Overview and IntroductionRead full article
But use of Kyoto mechanisms and carbon sinks required
There has been a lot of buzz in recent years about the EU-2020 emission reduction targets. So much in fact, that we might quite easily forget that the first Kyoto goal set by the European Union has still not been achieved - the final date for that goal is 2012. This goal was established for the EU-15 and not for the EU-27 as are the 2020 targets. It prescribes an average annual emission level of -8% compared to the base year for the period from 2008 to 2012.Read full article
Ali Kazemi, Schweitzer Engineering Laboratories, Inc.Read full article
Casper Labuschagne, Schweitzer Engineering Laboratories, Inc.
A.F. Picanço, C de Salles, M.L.B. Martinez, P.C. Rosa, H.R.P.M. de OliveiraRead full article
A voltage dip is a Power-Quality phenomenon, often caused by short circuits in the electricity grid, in which the supplying voltage decreases during a short period of time (typically <2s). Some process components, such as variable speed drives and computers, are extremely sensitive to such dips, which may result in a complete process outage.Read full article