LED street lighting: A power quality
comparison among street light
technologies
A Gil-de-Castro PhD
a
, A Moreno-Munoz PhD
a
, A Larsson
b
, JJG de la Rosa PhD
c
and
MHJ Bollen PhD
b
a
Department of Computer Architecture, Electronics and Electronic Technology,
University of Cordoba, Cordoba, Spain
b
Lulea
˚
University of Technology, Electric Power Engineering, Skelleftea
˚
, Sweden
c
Department of Electronics, University of Ca
´
diz, Algeciras-Ca
´
diz, Spain
Received 14 March 2012; Revised 8 May 2012; Accepted 15 May 2012
High-pressure sodium lamps are currently the main lamps used in public lighting.
However, the possibility of using high-power light emitting diode (LEDs) for street
lighting is growing continuously due to their greater energy efficiency, robust-
ness, long life and light control. The aim of this paper is to study the power quality
of high-power lighting networks based on LED and high-pressure sodium lamps.
Both electromagnetic and dimmable electronic ballasts, which can dim the lamp
output smoothly and uniformly, have been used connected to high-pressure
sodium lamps. High-pressure sodium lamps connected to electronic equipment
have been tested with different arc power levels using dimming on a 230 V power
supply. The study presented in this paper is completely based on measurements,
including harmonic currents in the frequency range up to 150 kHz for all the
technologies. The main results show a broadband spectrum in LED lamps which
confirms other research in Fuorescent lamps powered by high-frequency ballasts.
Results also indicate a decrease in the harmonic value with increasing harmonic
order, and a decrease in the harmonic value at half load (60%) compared with full
load (100%). Although total harmonic distortion of the current is lower with high-
pressure sodium lamps connected to electronic rather than electromagnetic
ballasts, LED lamps achieved the lowest total harmonic distortion of current.
1. Introduction
The public lighting systems in our cities are a
basic and vital service for city councils and
other public administrations. On the one
hand, citizens demand high-quality service
in accordance with our highly developed
society. On the other hand, a lighting instal-
lation is an important consumer of energy
that is affected by factors such as regulation
and maintenance. A recent study carried out
for the European Commission
1
has shown
that between 30% and 50% of electricity used
for lighting could be saved by investing in
energy-efficient lighting systems. In most
cases, such investments are not only profit-
able and sustainable but also improve lighting
quality. The main recommendation
2
is that
streetlights and other forms of outdoor light-
ing should be made more efficient as part of
a comprehensive strategy to reduce CO
2
emissions, this strategy also including cleaner
Address for correspondence: Aurora Gil-de-Castro, Escuela
Politecnia Superior of Cordoba, Leonardo de Vinci Building,
14071 Cordoba, Spain
E-mail: agil@uco.es
Lighting Res. Technol. 2013; 45: 710–728
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options for electricity generation, reduced
vehicle emissions, more energy efficient build-
ings, and smart electric meters combined with
smart appliances which shift electricity use
from peak to off-peak periods. Sustainable
lighting technology should meet at least
three criteria: (i) high efficiency or energy
saving, (ii) long product lifetime and (iii)
recyclability.
2
A suitable selection of the lamp type
is important. The majority of light sources
used in public lighting are high-intensity
discharge lamps; but light emitting diode
(LED) lamps are being presented as a more
energy-efficient alternative. This is due to the
fact that LED lamps, unlike conventional
light sources, make a direct transfer of elec-
trical energy into light and are being strongly
promoted. 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.
3
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. Little power quality research has
been carried out on this technology; moreover
it is mainly focused on low power LEDs
4–6
and not on high-power LED street lights.
The minimum acceptable requirements
for lighting controls are that they provide
enough light for the users and reduce lighting
levels without compromising users’ satisfac-
tion and productivity. Therefore, by having
a good understanding of the lamps, ballasts,
luminaires and control options available
today, lighting can be produced that is
energy efficient, cost effective and of better
quality.
7
Results
8
show that it is important
to encourage the installation of smart dim-
mable electronic ballasts. As well as receiving
switching and dimming commands from a
streetlight segment controller such an instal-
lation can also be used to auto-detect lamp
and electrical failures.
To sum up, the following measures are
recommended for decreasing the cost of
public lighting
9
: Reduction of the luminance
level (dimming) during hours with reduced
traffic density. This will reduce electrical
energy consumption, which in turn will
lead to a cost reduction. Making the street
classification compliant with international
standards and establishing the light technical
parameters based on this classification.
Setting a special price for the electric energy
used by public lighting, due to the consump-
tion during the night. Installing a street
lighting control system which makes it pos-
sible to minimise maintenance expenses by
better managing the replacement of failed
lamps through knowing their location in
addition to the age of each lamp. This last
proposal implies the introduction of a wireless
control system,
10
which has advantages over
other systems based on power line communi-
cation (PLC) protocols. Upgrading street
lighting using lighting equipment with low
radio frequency emissions, not only within the
low but also within the high frequency range,
can improve the power quality in the whole
system, avoid malfunction of electronic
equipment and allow the working of PLC,
and save costs.
The reminder of this paper is organised as
follows: Section 2 outlines the background to the
paper. Results of an experiment with LED lamps
and HPS lamps working from electronic
and electromagnetic ballasts are shown and
explained in Sections 3 to 5. Later Section 6
compares the results obtained in th e experiments.
Finally Section 7 offers some conclusions.
2. Background
The characteristics of the different lamp
technologies used in public lighting are
summarised in the Table 1.
Power quality of street light technologies 711
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A number of compatibility problems have
occurred in the field of lighting as a result of
installing electronic ballasts in energy-saving
lamps in general without understanding how
to avoid such problems. Examples of the
problems include
11
early failure of ballasts
and lamps and malfunctions of energy man-
agement systems, centralised clock systems,
infrared-based remote controls and personal
electronic devices such as a hearing aids,
among others.
Lighting also affects the power quality
(PQ) of the electrical distribution system.
PQ is concerned with deviations of the
voltage or current from the ideal single-
frequency sine wave of constant amplitude
and frequency. A consistent set of definitions
can be found in Moreno-Mun
˜
oz.
12
Poor
PQ is a concern because it wastes energy,
reduces electrical capacity, and can harm
equipment and the electrical distribution
system itself. PQ deterioration is due to
transient disturbances (voltage sags, voltage
swells, impulses, etc.) and steady state dis-
turbances (harmonic distortion, unbalance,
flicker). This paper is focused on the latter,
and, specifically, on harmonic distortion.
13
The study presented in this paper is com-
pletely based on measurements. It follows
other studies,
14,15
which present work on
harmonics due to street lighting using both
electromagnetic and electronic ballasts. Those
ballasts were used connected to up to three
lamps. The experimental results presented
here include the introduction of the LED
lamp within that harmonic study.
The main objective must be to provide
guidelines for minimising any PQ impacts
resulting from the application of energy-
saving technologies with regards to lighting.
The primary focus of this paper is both LED
and HPS lamps for street lighting. Energy
saving is often used as one of the selling
features for these devices and customers need
Table 1 Main characteristics of lamp technologies
LED lamp HPS lamp and electronic ballast HPS and electromagnetic ballast
Long operating life (50 000 hours
life with 70–80% lumen
maintenance)
Long lifetime (from 40 000 to
60 000 hours)
Long lifetime (430 years at 1058C)
Very low power consumption Increased lamp life (on average up
to 30% longer lamp life)
Low cost
Low installation and maintenance
costs
No flickering effect Suitable for extreme weather conditions
(humidity, temperature variation, lightning)
Harmonised illumination Dimmable Recyclable materials (magnetic chokes are
recyclable)
High efficiency High efficiency (up to 15% savings) Self-recovery feature (when the ac mains
voltage recovers after a disturbance)
Dimming possibilities Non audible noise Very low maintenance costs
Contain no hazardous materials Low weight Not dimmable
Low temperature and function well
in cold temperatures
Energy saving (up to 13%) Not energy saving
Good vibration resistant
characteristics
Relatively expensive Flickering effect
Quick start and re-start (do not
need to firstly cool the system as
with HID)
Not environmentally friendly No constant light output
Low glare and strobe-free
Free from ultraviolet or IR
Possible use with renewable
energies
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to have a clear understanding of the energy-
saving potential of these technologies.
Harmonic analysis is a primary aspect of
PQ assessment. With the widespread use of
power electronics equipment and nonlinear
loads in industrial, residential and commercial
office buildings, the modelling of harmonic
sources has become an essential part of
harmonic analysis.
16
This paper focuses
on the harmonic analysis of existing lamps
but also the lamp of the future, the LED
lamp.
As is well known upgrading to lighting
equipment with low emissions (high power
factor and low harmonic distortion) can
improve the power quality of the electrical
system. Furthermore, upgrading with higher
efficiency and higher power factor lighting
equipment can also free up valuable electrical
capacity. This benefit alone may justify the
cost of a lighting upgrade.
Another field of interest is the possible
interference with PLC (using a frequency
range 9–95 kHz) resulting in communication
losses. Two studies
17,18
distinguised five
different types of interactions between com-
munication and end-user equipment. One
interaction is due to the emission by end-
user equipment, but the most important is
due to the low impedance created by end-user
equipment. They will all cause the communi-
cation system not to work.
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. 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 2010
19
), among
others. On the other hand, some drawbacks
include the need for effective cooling, and the
most determining aspect, the price, although
this is becoming less.
In this section, an experiment including
LED street lights has been developed.
The experiment has involved the individual
monitoring of two different LED lamps. The
current taken by the lamps was measured
using a Dranetz PX5 power-quality monitor
in order to obtain 1-second values for all the
typical power-quality parameters as well as
a 200 ms waveform of the voltage and
current every minute with a sampling fre-
quency equal to 12.8 kS/s. The measurement
was carried out in day time to avoid disturb-
ing the night traffic. Switch-on and switch-off
processes were forced and the parameters of
the lamps were registered during steady state
and warm up.
The first street light monitored was a
Thorn lamp, with an active power of 25 W,
and according to our measurements other
values are 6.8% total harmonic distortion of
the current (THDI) and a displacement power
factor (DPF) of 0.96. First, regarding the
active power, the lamp was monitored over 30
minutes but it was not stable within that time.
In fact, the active power is decreasing over
time. The variation is relatively low (2.6%),
but even after 30 minutes, the lamp did not
achieve stabilisation of the active power. This
can be explained by the dependence of the
LED on temperature.
20
The forward voltage
drops with temperature which leads to a
decrease in the power. Also, the variation of
the temperature of the aluminium base and
fin with operating time was recorded. Even
after about 3 hours the temperature was still
increasing.
21
This fact could be the reason for
the decreasing tendency in the LED active
power.
Second, both the voltage and current
waveforms of the LED street light lamp are
represented in Figure 1. The almost pure
sinusoidal waveform of the current can be
seen but there are also some spikes around the
zero-crossing.
Power quality of street light technologies 713
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Later on, in order to study the distortion in
this technology, the odd harmonic spectrum
of the current up to 2500 Hz was measured.
The result is shown in Figure 2. The harmonic
groups, as defined in IEC 61000-4-7,
22
have
been calculated for each of the 60 basic
measurement windows of 200 ms duration,
obtained at 30-second intervals. Shown in
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
3 7 11 15 19 23 27 31 35 39 43 47
THD
Harmonic order
Current (mA)
Current (%FND)
7 11151923273135394347
Figure 2 Harmonic current spectrum from a LED street light lamp in milliaamps and percentage of fundamental
400
200
0
–200
Voltage (V)
Current (A)
–400
20 40
Time (ms)
60 80
0.2
0.1
0
–0.1
–0.2
Figure 1 Current (solid) and voltage (dash-dot) waveforms for a LED street light lamp
714 A Gil-de-Castro et al.
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