Elhuyar Fundazioa - Basque Research

Efficient light bulbs are also affected by variations in brightness caused by the mains


Courtesy of Elhuyar Fundazioa - Basque Research

Until now the new lighting technologies, in other words, more energy-efficient lamps,have been assumed to be less sensitive than the incandescent bulbs to voltage fluctuations in the electrical power supply, one of the most striking disturbances. The research group Signal and Communications Group (GSC) of the UPV/EHU’s Faculty of Engineering in Bilbao has conducted a thorough analysis of the response of these new technologies, bearing in mind the actual conditions of the mains, to be able to determine how valid these assertions are. As they have been able to observe, this assertion is not always proven, and what is more, there are moments when the sensitiveness is greater than that of the traditional incandescent bulbs.

The variations in the brightness of the bulbs caused by voltage fluctuations of the electricity supply itself are known as flickers and can on occasions be a nuisance for users and cause them discomfort.“The main reason why these fluctuations may occur is industrial machinery that consumes a lot of electrical power at certain moments,' explained Izaskun Azcárate, a researcher in the UPV/EHU’s Signal and Communications Group.

With the entry onto the market of new lighting technologies, like compact fluorescent lamps (CFL) and LEDs, it was necessary to determine once again their sensitivity when subjected to voltage fluctuations.The first pieces of research, published in 2008, “indicated that the new lamps were less sensitive than the incandescent ones and thereforeno changes in their brightness occurred when there was the same fluctuation in mains voltage,” said Azkarate.
On the basis of these results, various international standardisation organisations have begun to propose changes in this aspect. Two changes have been proposed: to adjust the flicker meters to the new reference lamps or else increase the established limit.

Analysing complex signals

Measurements were taken using a set of lamps subjected to different types of voltage fluctuations.Firstly, they used standardized fluctuations (analytic signal), and in a second piece of work they used actual fluctuations,which tend to be more complex, registered in four locations in the north of Spain. They concluded that there are three different behaviours: there are lamps that are less sensitive than the incandescent lamps; there are ones that reach the levels of the incandescent ones or even surpass them; and there are others that respond differently depending on the actual signal applied.

“These results cast doubt on the reduced sensitiveness to voltage fluctuations of the new technologies, and reveal that sensitiveness does not depend only on the lighting technology but also on the complexity of the voltage fluctuation and the actual scenario in which the lamp is used,” concluded the researcher. “That way,” she added, “both the proposal to raise the flicker limits and the one involving the seeking of a new reference lamp appear unworkable”.

“The solution could be geared towards controlling the response of the lamps during the design process.To do that, it would be necessary for no lamp to display any sensitivity greater than that of the incandescent bulb,” she stressed. In other words, as the research concluded, by maintaining the current flicker threshold, a test protocol should be established whereby each manufacturer could check that in these conditions the lamp does not exceed the threshold.

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