10-04-2012, 02:29 PM
Development of Zigbee based Street Light Control System
Zigbee streetlight project.PDF (Size: 218.96 KB / Downloads: 113)
Abstract
Industry of street lighting systems are growing
rapidly and going to complex with rapid growth of industry and
cities. To control and maintain complex street lighting system
more economically, various street light control systems are
developed. Nevertheless most of developed systems have some
drawbacks.
So we are going to develop new light control system which can
overcome old systems drawbacks. We surveyed various street
light control systems and analyzed its characteristics. Through
these efforts, we found that common drawbacks of most light
control systems are uneasiness of handling and difficulty of
maintenance. To reduce uneasiness of handling and difficulty of
maintenance in operating light control system, we designed new
street light control system by using Zigbee communication
technique.
In this thesis, we describe on the H/W design of new street
light control system designed by using Zigbee communication
protocol.
Index Terms— H/W Design, Remote Control terminal, Street
Light Control System, Zigbee,
I. INTRODUCTION
Treet light control system is a centralized system which
control and monitor status of street lights installed
alongside load. Lights are switched to ON/OFF by this
system’s control command. Its local status information is also
monitored by control system via communication channel.
Status information which is monitored are on/off status
information, energy saving mode status, control group status
information and safety related information, etc.
To transfer control command and status information
between street light control system and remote street light
control terminals which installed at each light pole, various
communication media and communication protocols are using.
As communication media, wireless or power lines are used
generally. Various frequency bands from tens of MHz to RF
bands are used for wireless case.
This work was supported by the Korea Ministry of Science and
Technology.
J. D. Lee is with Korea Electrotechnology Research Institute, Chang-won
City , 641-600, Korea (e-mail: jdlee[at]keri.re.kr).
H. S. Ryoo is with KERI (e-mail: hsryoo[at]keri.re.kr).
S. B. Choi is with KERI (e-mail: sbchoi[at]keri.re.kr).
K.Y. Nam is with KERI (e-mail: kynam[at]keri.re.kr).
S. H. Jeong is with KERI (e-mail: shjeong[at]keri.re.kr).
D. K. Kim is with KERI (e-mail: dkkim[at]keri.re.kr).
The reason of why these media are used mainly is its
easiness of installation and maintenance. There are no needs
to install additional transmission line and it is more
economical than other media’s case.
Compare to wireless channel, PLC lines have some
advantages. PLC based control system is easy to design
because there are no obstacles to communication path. It does
not need additional wire for communication and repeaters
which used for RF communication system sometimes to evade
obstacles like buildings.
But it has disadvantages also. Price of remote controller is
higher than that of wireless case and there are no
communication way when if short circuit problems aroused.
For the case of short circuit in the middle of power line,
remote terminals following short circuit point can’t transfer
data. So, control system can’t read status information on short
circuit and operators can’t do any action immediately and it
can cause fatal safety problems.
Electrical shock was longtime problem of electrical power
system since usage of electricity. Still it is main problem of
electric power supply system, especially for street light control
system because it is installed at open space and along the
roadside through long distance. Heavy rain, traffic accident,
etc make big trouble sometimes. So every street light control
system should make countermeasure on safety problem.
Maintenance is also one of main consideration factor. Every
street light control system operators want to reduce
maintenance costs and number of person for repair. To reduce
costs and number of person, street light control systems
should have high stability and can give required information
when operators need information for maintenance and
operation. For these reason, reliable communication path and
technique that is adequate for street line control system is
required.
We designed new street light control system that is reliable
and cost effective by using Zigbee communication system
technique. For that, we surveyed characteristics of street light
control systems and tried to enhance safety level.
In this paper, we describe on new street light control
system we designed.
In following section 2, we will describe on requirement
analysis on street light control system. We represent on
communication channel characteristics, system design factors,
and system H/W design, etc. In chapter 3, detailed H/W
design including block diagram will be described.
S
142440178X/
06/$20.00 ©2006 IEEE 2236 PSCE 2006
II. DESIGN OF NEW STREET LIGHT CONTROL SYSTEM
A. Requirement Analysis for Street light Control System
In Korea, local government authorities are responsible for
the operation of street light control system. Every local
government authorities have facility maintenance department
to manage street light and guard ramps. As local governments
are trying to reduce management costs and operators, the need
of remote light control system is increasing. So every local
government is introducing new systems that can be useful for
street light control. As there is no standardized rule or code on
street light control system, various systems are used.
To develop new light control system, we surveyed and
analyzed state-of-the-art of street light control systems.
Through the analysis of various street light control systems,
we found some basic characteristics which are common
characteristics in most of light control system.
Most of systems are using earth leakage circuit breaker
and main circuit breaker to on/off street lights. Also, most of
systems can’t detect each lights status and can’t control each
light. Most of systems are using group base control.
Although, one of main purposes of the street light control
systems are protects people from electrical shock, systems
which running nowadays can’t do it well because all systems
are using group base control. By using group base control,
controlling and gathering status information of individual
lights is impossible. So, if there is an short circuit but
impedance of overall of feeder circuit is still high enough,
main circuit breaker do not work and this makes big problem.
We tried to develop new street light control system which can
solve these problems.
Street light control systems are composed of three parts,
centralized control center, remote concentrator and street light
control terminals. But most of systems do not have street light
control terminal. Also role and function of remote
concentrator is simple in group base control scheme.
Centralized control center for street lights are reside in
local government office usually. At the centralized control
center, operators monitor and control street lights by using
operator’s terminal. Centralized control center computers
communicate with remote concentrator which control lights
installed alongside every road.
Remote concentrators control lights and gather status
information. Remote concentrators usually control 16 to 20
lights that are connected to power delivery feeder, 60Hz 220V.
Control and gathering information can be done group base or
individually. Whether do control group base or do control
individual base inference system operation costs and control
system costs. Systems that use group base control is cheaper
than that of individual case but simple in its functionality.
Most of street light control systems are using group base
control nowadays.
But group base control scheme of street lights have some
drawbacks. For group base control, all of light will be off
when there is a fault at just one light or pole. To solve this
critical handicap and safety problem that can be stem from
current leakage, we are trying to develop new street light
control system that can control light individually.
Third components of street light control system is street
light control terminals. To control each light individually, this
street light control terminal is needed. It is installed to every
light pole to detect status of light and to control lights. It
communicate with remote concentrator to give and receive
command and status information for control centor.
According to our survey on street light control system, span
between light poles are within 100m and about 16 to 20 poles
and lights are installed alongside road. So if a communication
system or protocol can address tens of controllers and can
transfer data within 100m, it can be useful candidate for street
light control system.
We surveyed various communication systems and
compared its characteristics. Among them, PLC and Zigbee
communication systems were best candidate.
As mentioned in section I, PLC communication system has
some advantages compared to wireless communication
systems. But price of remote controller is higher than wireless
case and there are no communication way when if short circuit
problems arouse. For the case of short circuit in the middle of
power line, remote terminals following short circuit point
can’t transfer data. So, there is no way of transferring status
information. In this case, operators can’t do any action
immediately and it can cause fatal safety problems.
As mentioned earlier in this section, group based control
scheme has problems and one of our research purpose is
overcome this drawback. PLC communication was one of
good candidate, but it is not adequate for individual light
control and our system design. So we designed new street
light control system by using Zigbee communication protocol.
B. Street light Control System Design by using Zigbee
Communication Protocol
Zigbee is rising communication protocol that can be used
for wide range of application. Although it do not have
broadband characteristics, its low price and adequate
communication characteristics, for example low power
consumption, makes it good candidate for communication
protocol. Followings are some list of main characteristics.
Data rate : 250 kbps(2.4 GHz)
Power consumption : 60mW
Distance : up to 100m
According to our survey on street light control system, data
rate of maximum 10kbps is sufficient. Zigbee’s relatively low
data transfer capacity is not make any handicap and we can
reduce data rate to improve reliability of data transfer.
Short communication distance also does not make any
problem. Span between light poles are within 100m, and this
is sufficient for communication because we can transfer data
to more long distance by reducing data rates.
2237
AS mentioned earlier, street light control system is
composed hierarchically. Centralized control center are
communicate with remote concentrator. Remote concentrators
communicate with each remote street light control terminal
which installed in every light pole. Remote concentrator’s
roles are control of individual remote controller and gathering
of status information from remote control terminals.
Figure 1 is block diagram of remote street light control
terminal which controls and stores each individual light and
its status.
Fig. 1. Block diagram of remote street light control terminal
Remote street light control terminal have I/O channels to
control light and analog input channel to measure status
information like voltage and current. Every light pole will
have switch like Earth Leakage Breaker to improve safety
level, and individual light will be monitored and controlled by
analyzing measured voltage and current value, information
related with control group, etc.
Figure 2 is block diagram of remote concentrator which
controls and stores each individual light and its status via each
remote street light control terminal.
Fig. 2. Block diagram of remote concentrator
As you see in figure 2, remote concentrator has LCD and
CDMA module, which remote street light control terminals do
not have. LCD module is added for easy maintenance.
Operators can easily know what is problem to repair by using
information that displayed on LCD module. All information
on the lights can be read at field from LCD, thus make
maintenance easy.
CDMA modem is added to transfer information between
concentrator and centralized control center. Concentrators
gather status information from each remote street light control
terminal and store it. Followings are remote concentrators
specification.
External I/F : RS-232C/RS-422 25pin(female)
Communication I/F : 2.4 GHz Zigbee and CDMA
Power Supply : 110/220V, 50/60Hz
Battery : Lithium(DC 7.2V, 1.2 AH)
Operating condition(-20~60C, 20~90% RH)
Remote concentrator has battery for emergency
communication for main power supply module’s outage. It has
two antennas, one for CDMA and another one for Zigbee
communication. It also has external interface for maintenance
operation.