LED street lighting: A power quality comparison among street light technologies
Summary (2 min read)
1. Introduction
- The public lighting systems in their cities are a basic and vital service for city councils and other public administrations.
- On the other hand, a lighting installation is an important consumer of energy that is affected by factors such as regulation and maintenance.
- At the moment LED lamps are not commonly used in street lighting systems, although recent technology is gradually improving the LED efficiency and color quality in comparison with high-pressure sodium (HPS) lamps, which allows their application in lighting systems.
- Results of an experimentwithLED lamps and HPS lamps working from electronic and electromagnetic ballasts are shown and explained in Sections 3 to 5.
2. Background
- The characteristics of the different lamp technologies used in public lighting are summarised in the Table 1.
- Very low power consumption Increased lamp life (on average up to 30% longer lamp life) Low cost Low installation and maintenance costs Harmonic analysis is a primary aspect of PQ assessment.
- Another field of interest is the possible interference with PLC (using a frequency range 9–95 kHz) resulting in communication losses.
3. Experiment with LED street lamp
- Lighting designed for outdoor applications must address multiple issues such as proper light distribution, glare, light pollution, energy usage and lifetime.
- Measurements have also been made of the harmonic spectrum within the high frequency distortion (from 2 to 150 kHz).
- After studying this LED street lamp, another LED lamp with high power was also recorded and analysed.
4. Electronic ballasts connected to HPS lamps
- Electronic ballasts have been promoted as replacements for electromagnetic ballasts for the last decade.
- Further, the use of electronic ballasts makes it possible to deliver constant power to the lamp during its entire useful life, unlike electromagnetic ballasts where the output power is dependent on lamp impedance variations.
- In order to have a stable current, the spectrum was measured over 4500 consecutive 30-second intervals.
- There is another peak around 110 kHz, which could also be related to the switching pattern used.
5. Electromagnetic ballasts connected to HPS lamps
- Conventional electromagnetic ballasts are equipment commonly used in old fashioned street lighting and consist of a magnetic choke, a starter, and a power factor correction capacitor.
- The LED lamp draws 0.25 A while the HPS lamp with the electromagnetic ballast draws 0.5 A. Moreover, the THDI from 0 to 2 kHz has been included within the right hand figure.
- The first remarkable aspect is the high values for harmonic orders up to the 17th, and a decrease in the higher frequencies.
6. Comparison of all experiments
- The main benefit of reducing the THDI in street lighting lamps occurs because such lamps are always connected in groups, so the total emission can be large.
- Specifically, the fundamental of the current, total harmonic distortion of the current (THDI), reactive (S) and active (P) power, and the displacement power factor (DPF) have been measured.
- 710–728 at CADIZ UNIV on April 27, 2015lrt.sagepub.comDownloaded from However, within the frequency range 9– 150kHz, the HPS lamp with the electromagnetic ballast has a lower emission than the one with the electronic ballast, also known as 2013; 45.
- Also in this frequency range the LED lamp has the lowest emission.
7. Discussion
- In this paper a harmonic analysis on HPS and LED street lights is presented.
- To this end, several experiments were carried out, two tests with two LED lamps, and two tests with HPS lamps connected to electromagnetic and electronic ballasts.
- Even in percentage terms, such LED and HPS lamps have lower emissions.
- But the pattern is not the same because it changes with higher harmonic orders.
- Regarding the high-frequency spectrum, two peaks have been observed in these spectra for the LED lamp and the HPS lamp Lighting Res. Technol.
8. Conclusion
- Various types of lamps used for street lighting have been analysed for their electrical properties using laboratory measurements.
- The measurements presented in this paper show that the harmonic emission from LED street lamps is less than that from HPS lamps.
- Replacing HPS lamps with LED lamps will thus not result in an increase in harmonic levels in the grid.
- In the frequency range above 9 kHz the emission from the electronic ballast is higher than from the electromagnetic ballast.
- The authors would like to thank the Spanish Ministry of Industry, Tourism and Trade for funding the Project TSI-020100-2010-484 (TASA) which partially supports this work.
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Frequently Asked Questions (13)
Q2. What are the future works mentioned in the paper "Led street lighting: a power quality comparison among street light technologies" ?
It is therefore important to perform regular measurements of the harmonic emission of LED street lamps so as to prevent power quality problems in the future.
Q3. What are the main issues that must be addressed when designing lighting for outdoor applications?
Lighting designed for outdoor applications must address multiple issues such as proper light distribution, glare, light pollution, energy usage and lifetime.
Q4. What are some advantages of dimmable electronic ballasts?
To sum up, some advantages of dimmable electronic ballasts are their energy savings (up to 50%), wider dimming range through wired or wireless central dimming control, and their robustness and reliability.
Q5. What is the highest current peak for electronic ballasts connected to HPS lamps?
Regarding the high-frequency spectrum, the highest current peak is reached by electronic and electromagnetic ballasts connected to HPS lamps, being 3mA (around 1% of FND) for the electronic ballast and 6mA for the electromagnetic ballast (2% of the FND).
Q6. What is the current of the LED street light?
The first street light monitored was a Thorn lamp, with an active power of 25W, and according to their measurements other values are 6.8% total harmonic distortion of the current (THDI) and a displacement power factor (DPF) of 0.96.
Q7. What is the main benefit of reducing the THDI in street lighting lamps?
The main benefit of reducing the THDI in street lighting lamps occurs because such lamps are always connected in groups, so the total emission can be large.
Q8. What is the role of the Department of Energy in the development of solid state lighting?
As an example, the U.S. Department of Energy acts as a catalyst to drive R&D breakthroughs in efficiency and performance, and to equip buyers to successfully apply solid state lighting.
Q9. Why is the interaction between the end-user and the lamp of the future important?
One interaction is due to the emission by enduser equipment, but the most important is due to the low impedance created by end-user equipment.
Q10. What are the advantages of LED lighting?
Although it is not widely used in street lighting, there are many advantages from the use of LED lamps such as very low power consumption, and high efficiency (124 lm/W in 201019), among others.
Q11. What is the effect of the switching frequency in the LED lamps?
From this the authors can conclude that in the LED lamps, the peak around 40 kHz is also due to the switching frequency of the active power factor correction circuit.
Q12. What is the trend of the LED lamp with the electronic ballast?
The trend followed by the two spectra from the HPS lamp with the electronic ballast and the LED lamp both show a peak (one around 2.8 kHz and the other around 6.1 kHz), whereas the trend of the HPS lamp with the electromagnetic ballast shows a decreasing tendency.
Q13. How does the lamp perform after 4 minutes?
It is possible to see that after 4 minutes the lamp appears to be stable in Watts (Figure 10), but if the authors remove the four first minutes, a decreasing tendency also appears.