Necessity of saving power for road lamps

Power grid operation rules supports light energy conservation: The allowable voltage deviation of lighting distribution system specified in national standard GB/T 12325 - 2008 is -10% and +7% of 220 V nominal voltage. With the change of power consumption peak and valley in real life, the voltage of lighting system fluctuates, so the lamp voltage is higher than 220 V and even exceed the upper limit of national standard (235 V). In the case, the relatively high voltage will be transformed into heat, reducing lamp service life and increasing unnecessary power consumption. Therefore, to reduce and stabilize voltage means saving energy and protecting lamps.

The electrical and optical properties of lamp provide space for power saving: As shown in the figure, if the lamp overvoltage is 10%, the service life will be reduced by half. By contrast, the service life will be doubled if the undervoltage is 10% but the illuminance is 7% attenuated than rated status. Therefore, to reduce the voltage below the rated one properly does not affect lighting quality. As for the HIDs are largely used in lighting project, rated working voltage is needed only when they are started. The voltage can be reduced properly after HIDs are turned on and voltage can be stabilized to maintain normal illuminance.

The aging properties of lamp provide space for power saving: The maintenance coefficient of gas discharge lamp is generally 0.8-1.6 which can make the lamp luminance 20%-40% higher than designed luminance (the luminance when the service life expires). When the service life of lamp expires, its luminance just reaches the target designed value. Due to the characteristics, the voltage can be reduced properly and stabilized to save power on the basis of ensuring normal luminance.

Human illumination engineering supports light energy conservation: The sensitivity of humans’ eyes to luminance is not in linear relationship but logarithmic relationship. It means that when the ray illuminance is increased by 10 times, people could feel that luminance is increased by once. People will enter “insensitive visual area” after reaching the sensitivity limit. Vision is reduced by 1% when the light intensity is reduced by 10% but it is hard to perceive by human’s eyes. Therefore, lighting energy saving can be realized without affecting the lighting effect that human body can perceive.