Public street lighting is an important concern and needs a special attention by authorities in developing countries because of its importance for stability in social as well as economic aspects.
Public lighting account 10–38% of total energy bill in typical cities worldwide. All countries allot a huge percentage of their budget for street lighting. Inefficiency leads to wastage of financial resources. Implementation of efficient lighting can reduce energy usage drastically (often by 25-60%). The Bureau of Energy Efficiency (BEE) in India has estimated the gross energy consumption for public lighting has become greater than twice that of energy usage five years before. Thus street lighting power usage increases every year with the growth of industrialization 1,2,3. BEE is laying down standards for street lights. The power usage by the street lights should be regulated to improve efficiency.
The conversion of street lights into LED lamps will reduce the energy bill for street lighting. But the disadvantages in installing LED (light emitting diode) lamps are as follows:High capital investment.Replacement of conventional lighting system.Investment return duration is longer.
The energy used for street lighting can be reduced by using other advanced street lighting schemes. But replacing all the existing conventional magnetic ballast driven HID (high intensity discharge) lamps is costlier and lead to wastage of all those HID lamps since it cannot be used for recycling process. The lighting system must adjust to the basic illumination levels of the region according to the utilisation of lights. The street lighting can be defined by two categories like peak time and off peak time based on the number of passerby in the defined region under illumination. The street lights should be set such that the illumination level must be high during peak time and it must fall during off-peak time.
Thus voltage control based on the passerby count will reduce the energy usage.This leads to reduced energy usage by the lighting systems when compared to the operation under constant voltage or constant level of illumination.Traditionally, the voltage control is done by switches and tapped transformers.
Multiple-tapped autotransformers have some disadvantages, because the use of this bulky, lossy (on low-dimming levels) and expensive component implies a limited margin of regulation. For Street lighting, this can be considered by forming three independent single phase into three phase. According to above considerations, this new AC voltage regulator for the control of the public lighting systems is proposed with continuous regulation of the output voltage, with a theoretical margin of regulation between 0-100 % and without using an autotransformer.