AN EFFICIENT MONITORING OF SUBSTATIONS IN
POWER TRANSMISSSION LINES USING ZIGBEE IN EMBEDDED SYSTEM
ABSTRACT
This project proposes an innovative design to develop a system based on microcontroller
that is used for monitoring power of a distribution transformer in a substation
and to protect the system from the rise in above mentioned parameter.
Protection to the distribution transformer from the main station is done with
the aid of the ZIGBEE Communication. Moreover the system displays the same on a
LCD at the main station that will lead to avoid the damage in substation. The
design generally consists of two units, one in the substation unit, called as
transmitter unit, and another in the Main station called as controlling and
receiver unit. The transmitter in the substation is where the power is
monitored continuously by PIC microcontroller. A ZIGBEE is used for
transmitting the signals that are obtained. The controlling unit in the main
station receives the transmitted signals by means of ZIGBEE receiver and
displays in LCD and LED and reacts in accordance to the received signal.
Keywords: PIC microcontroller, LCD, LED, ZIGBEE, Main-Substation.
INTRODUCTION
Electricity is a necessary and useful form of energy. It plays an ever
growing role in our modern industrialized society. Maintenance of a transformer
is one of the biggest problems in the Electricity Board (EB). The transformer
may burn out due to the over load and short circuit in their winding. Power
starts from the transmission grid at distribution substations where the voltage
is stepped-down and carried by smaller distribution lines to supply commercial,
residential, and industrial users.
Electric power systems can be divided into two stations, namely, Main
station and Substation. Power to the substation is monitored using PIC
Microcontroller and transmitted through ZIGBEE, then the main station receives
the signal and compare with the reference voltage. Because of the
microcontroller operation in the main station, if the increase in power rises
higher than the desirable power, then that increased range is viewed by LCD and
indicated using LED and BUZZER. And further damage can be avoided by shutting
down the substation.
WORKING PRINCIPLE
The substation contains ZIGBEE transmitter and PIC microcontroller. The
main station consists of PIC microcontroller, ZIGBEE receiver and LCD display.
The power in the substation is continuously acquired by the PIC Microcontroller
and transmits through the ZIGBEE transmitter to the main station. The ZIGBEE receiver
in the main station receives the signal and compares it to the reference
voltage. If the received signal is below the reference voltage it does not
shows any variation or if it is above the reference voltage then that increased
range is viewed by LCD and indicated using LED and further damage can be
avoided by shutting down the substation using relay from the main station.
HARDWARE DESCRIPTION
Figure.1 Block diagram
A. PIC MICROCONTROLLER: The controller PIC 16f877A is used in this project.
It is 8-bit CMOS microcontroller with flash program it is RISC PROCESSOR with
performance, fully static design it has 5 ports. Port A, Port B, Port C, Port D
and Port E with 33 I/O lines. The Controller has 8kx14 words of flash memory,
368x8 bytes for data memory and 256x8 EPROM data memory. It is programmable
code protection. The user code will be stored in the flash memory. The 5V
supply is given to VDD and VSS of the controller. Microcontroller is used for
monitoring power of a distribution transformer in a substation and to protect
the system from the rise in that parameter.
B. ZIGBEE: ZIGBEE is based on an IEEE 802.15.4 personal area network. The
technology defined by the ZIGBEE specification is intended to be simpler and
less expensive than other WPANs, such as Bluetooth. ZIGBEE is targeted at Radio
Frequency (RF) applications that require a low data rate, long battery life,
and secure networking. ZIGBEE has a defined rate of 250 kbps. In substation
unit the power is continuously monitored and it is transmitted through ZIGBEE transmitter
and the transmitted signal is received by ZIGBEE receiver.
Figure.2 Zigbee module
C. TRANSMITTER SECTION: Each of the two transmitters is a CMOS inverter
powered by + 10V internally generated supply. The input is TTL and CMOS
compatible with a logic threshold of about 26% of Vcc. The input if an unused
transmitter section can be left unconnected: an internal 400KW pull up resistor connected between the transistor input and Vcc will pull
the input high forming the unused transistor output low. The open circuit
output voltage swing is guaranteed to meet the RS232 specification + 5v output
swing under the worst of both transmitters driving the 3KW. The slow rate at output is limited to less than 30V/ms and the powered done output impedance will be a minimum of 300ohm with
+2V applied to the output with Vcc =0V.The outputs are short circuit protected
and can be short circuited to ground indefinitely.
D. RECIEVER SECTION: The two receivers fully conform to RS232 specifications.
They’re input impedance is between 3KW either with
or without 5V power applied and their switching threshold is within the +3V of
RS232 specification. To ensure compatibility with either RS232 IIP or TTl\CMOS
input. The MAX232 receivers have VIL of 0.8V and VIH of 2.4V the receivers have
0.5V of hysteresis to improve noise rejection. The TTL\CMOS compatible output
of receiver will be low whenever the RS232 input is greater than 2.4V. The
receiver output will be high when input is floating or driven between +0.8V and
–30V.
E. CIRCUIT DIAGRAM EXPLANATION: Figure.3 shows the circuit diagram. The
reference voltage is fixed in the c program coding. A potentiometer is
connected to the reference pin-2 in U2 PIC Microcontroller. The signal is transmitted
from U2 controller TX pin-25 via ZIGBEE transmitter. The transmitted signal is
received by ZIGBEE receiver and fed to U1 controller RX pin-26. The port C and
port D is connected to LCD Display. The LED and Buzzer is connected to port B
Pin 33 and 34.
Figure.3 Circuit diagram
Figure.4 Final Hardware Arrangements
SOFTWARE DESCRIPTION
A. MPLAB: MPLAB IDE is an integrated development environment that provides
development engineers with the flexibility to develop and debug firmware for
various Microchip devices. MPLAB IDE is a Windows-based Integrated Development
Environment for the Microchip Technology Incorporated PIC microcontroller (MCU)
and PIC digital signal controller (DSC) families. In the MPLAB IDE, you can:
· Create source code using the built-in editor.
· Assemble, compile and link source code using various language tools.
B. CCS C COMPILER: It offers the most optimized Microchip PIC MCU and dsPIC
DSC C Compilers for Windows and Linux, and a powerful integrated development
environment. Our compilers support the PIC10, PIC12, PIC14, PIC16, PIC18
microcontrollers and now support Microchip PIC24/dsPIC chips. The CCS C
Compiler includes generous libraries of useful routines and ready-to-run
example programs for hardware peripherals. This compiler is used to compile the
embedded c language program.
C. MPLAB SIMULATOR: PROTEUS is a discrete-event simulator for the running
the hex code program. It’s used to debug the software before going to hardware.
D. PCB DESIGN: PAD 2 PAD is used to prepare the PCB schematic. Tracks are
made in insulating base. PCB's are used to route electrical signal through
copper. The performance of an electronic circuit depends up on the layout and design
of PCB.
E. PCB PREPARATION: Layout is printed on a butter paper. It is screen
printed on copper clad, etched by using ferric chloride solution, drilled using
PCB driller, cut the unwanted materials and soldered the components.
Figure.5 PCB Design For PIC Microcontroller
CONCLUSION
This design based on PIC microcontroller is used to monitor and control the
power in the distribution transformer continuously throughout its operation. If
the microcontroller recognizes any increase in the level of desired value, then
the unit has been made shut down in order to prevent it from further damages
and also indicates the values throughout the process in LED and Buzzer and
displays the value in LCD. Hence the distribution is made more secure, reliable
and efficient by means of the proposed system.
REFERENCES
[1] Embedded C Programming and the Microchip PIC” by Barnett & Cox
O’cull,Thomson, 2006.
[2] Design with PIC Microcontroller by John Bheat Man, Prentice Hall, 1997.
[3] PC-Based Instrumentation Concepts and Practice by N.Mathivanan,
PHI Learning, 2007.
[4]The 8051 Microcontroller and Embedded Systems using Assembly and C by
Muhammad Ali Mazidi, Pearson, 2009.
[5] P.Daponte, M. Di Penta and G.Mercurio, A Distributed Measurement System
for Power Quality Monitoring, IEEE Transactions on Power Delivery, Vol. 19,
Issue. 2, pp: 456-463, 2004.
[6] G. Pudlo, S. Tenbohlen, M. Linders and G. Krost, "Integration of
Power Transformer Monitoring and Overload Calculation into the Power
System Control Surface", IEEE/PES Transmission and Distribution
Conference and Exhibition, Vol. 1, pp: 470-474 Asia Pacific, 2002.
[7] Sen Ouyang and Jianhua Wang, "A new morphology method for
enhancing power quality monitoring system", International Journal of Electrical
Power & Energy Systems Vol.29, No.2, pp.121-128, February 2007.
[8] www.chipcon.com
[9] www.zigbeealliance.com
[10] www.microchip.com
[11] www.soselectronic.com
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