Notesale: Turn your study into money

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CHAPTER 1

INTRODUCTION
In power systems, distribution transformer is electrical equipment which distributes power to the
low-voltage users directly, and its operation condition is an important component of the entire
distribution network operation
...
However, their life is significantly
reduced if they are subjected to overloading, resulting in unexpected failures and loss of supply to
a large number of customers thus effecting system reliability
...
The monitoring devices
or systems which are presently used for monitoring distribution transformer exist some problems
and deficiencies
...

(1) Ordinary transformer measurement system generally detects a single transformer parameter,
such as power, current, voltage, and phase
...

(2) Detection system itself is not reliable
...

(3) Timely detection data will not be sent to monitoring centers in time, which cannot judge
distribution transformers three-phase equilibrium
...

(5) Many monitoring systems use power carrier communication to send data, but the power carrier
communication has some disadvantages: serious frequency interference, with the increase in
distance the signal attenuation serious, load changes brought about large electrical noise
...

According to the above requirements, we need a distribution transformer real-time monitoring
system to detect all operating parameters operation, and send to the monitoring center in time
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This will help
to identify problems before any serious failure which leads to a significant cost savings and greater
reliability
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1
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2 LIMITATIONS
Network area must be required for the proper operation of the system
...
Top and bottom oil temperatures, Ambient temperature, Load current, Oil
flow (pump motor), Moisture in oil, Dissolved gas in oil, Bushing condition, LTC monitoring, Oil
level
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Online monitoring system consists of embedded system, GSM modem, mobile-users and GSM
networks and sensors installed at transformer site Sensors are installed on transformer side which
reads and measures the physical quantity from the distribution transformer and then it converts it
into the analog signal
...
It is utilized to
acquire, process, display, transmit and receive the parameters to/ from the GSM modem
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It is the link between the embedded system and the public GSM
network
...

The server is attached to GSM modem and received transmits SMS from/to the transformer site
via the GSM module
...
It tells about the
design and working of the design with the help of circuit diagram and explanation of circuit
diagram in detail
...

3
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1 MAIN PART OF THE SYSTEM
1
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1 CURRENT SENSOR
1
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3TEMPRETURE SENSOR
2
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MICROCONTROLLER
4
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2 OVERVIEW OF WORKING
First sensors which are installed at the transformer site sense the various parameters of
transformers and convert into analog signal to be processed in signal conditioning circuits
Next the signal is passed through microcontroller
...
The built-in EEPROM
is used to save the online measured parameters along with their hourly and daily averages
...


5

This GSM modem then sends this SMS to mobile users containing information about
parameters value of the distribution transformers
...
3 CIRCUIT DIAGRAM OF THE MODEL

6

CHAPTER 2

BACKGROUND OF THE PROJECT
Abnormality in distribution transformer is accompanied with variation in different parameters like
Winding temperature
...
However, we are dealing with oil temperature and load current
...
The embedded module is located at the transformer site
...
The
second is the GSM module
...
The third is utility module that has a PC-based -server located at the utility control center
...


3

CHAPTER 2

BACKGROUND OF THE PROJECT
Abnormality in distribution transformer is accompanied with variation in different parameters like
Winding temperature
...
However, we are dealing with oil temperature and load current
...
The embedded module is located at the transformer site
...
The
second is the GSM module
...
The third is utility module that has a PC-based -server located at the utility control center
...


3

3
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2 POWER SUPPLY
Power supply is the circuit from which we get a desired dc voltage to run the other circuits
...
Hence a step-down transformer is used to get 12V AC which is later converted to 12V DC
using a rectifier
...
To remove the ripples and obtain smoothed DC power
filter circuits are used
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The 12V DC is rated down to 5V using a positive
voltage regulator chip 7805
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A 5V regulated supply is taken as followed:
Transformer - steps down high voltage AC mains to low voltage AC
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Smoothing – smooth the DC from varying greatly to a small ripple
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3
...
2
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Transformers work only with AC
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Step-up transformers step up voltage, step-down transformers steps down voltage
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Here a step down transformer is used to get 12V AC from the supply i
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230V AC
...
4
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2

RECTIFIERS

A rectifier is a circuit that converts AC signals to DC
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There are two types of rectifier circuits as Half-wave rectifier and Full-wave rectifier depending
upon the DC signal generated
...
4
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3 SMOOTHING
Smoothing is performed by a large value electrolytic capacitor connected across the DC supply to
act as reservoir, supplying current to the output when the varying DC voltage from the rectifier is
decreasing
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The capacitor
charges quickly to the peak of the varying DC and then discharges as it supplies current to the
output
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5 MICROCONTROLLER
Microcontroller is defined as a system on computer chip which includes number of peripherals
like RAM, EEPROM, etc
...
There are number of popular
families of microcontrollers which are used in different applications as per their capability and
feasibility to perform various task, mostly used of these are 8051, AVR and PIC microcontrollers
...
AVR is an 8-bit
microcontroller belonging to the family of Reduced Instruction Set Computer (RISC)
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The other type is CISC
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The microcontroller transmits and receives 8-bit data
...
The AVR family controllers have register based architecture which means that both the
operands for an operation are stored in a register and the result of the operation is also stored in a
register
...
Some of the key features of Atmega16
are:
·

16KB Flash memory

·

1KB SRAM

·

512 Bytes EEPROM

·

40-Pin DIP

·

8-Channel 10bit ADC

·

Two 8 bit Timers/Counters

·

One 16bit Timer/Counter

·

4 PWM Channels

·

In System Programmer (ISP)

·

Serial USART

·

SPI Interface

·

Digital to Analog Comparator
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6 ARCHITECTURE OF AVR
The AVR microcontrollers are based on advanced RISC architecture and it consist 32 x 8bit
general purpose working registers
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The ALU performs arithmetic as well as logical operations over
the inputs from the register or between the register
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AVR follows Harvard Architecture format in

which the processor which is equipped with the separate memories and buses for Program and the
Data information
...
Since AVR performs a single cycle execution, it means that AVR can
execute 1 million instructions per second if the cycle frequency is 1MHz
...
We should
optimize the power consumption with processing speed and hence should select the operating
frequency accordingly
...

2
...
The AT refers to
manufacturer Atmel, Mega means the microcontroller belong to Mega AVR category, 16 gives the
memory of the controller, which is 16KB
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It tells about the
design and working of the design with the help of circuit diagram and explanation of circuit
diagram in detail
...

3
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7
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ADC
reads the analog input for e
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, a sensor input and converting it into digital information which the
microcontroller understands
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7
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Timers are useful for generating
precise actions for e
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, creating time delays among two operations
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7
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Watchdog timer monitors continously
and resets the controller if the code is stuck at any execution action for more than a fixed time
interval
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7
...
The rest are internal
interrupts which is supported by the peripherals like USART, ADC, and Timers etc
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7
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3
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7 General Purpose Registers:
Atmega16 has 32 general purpose registers which are coupled directly with the Arithmetic Logical
Unit (ALU) of CPU
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7
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3
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9 DAC:
ATmega16 is also equipped with a Digital to Analog Converter (DAC) interface which can be
used for reverse action
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3
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10 Memory:
Atmega16 consist of three different memory sections:
1
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It is easily erasable electrically as a single unit
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e
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Atmega16 is available with 16KB of in
system programmable Flash EEPROM
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Byte Addressable EEPROM:
This is also a nonvolatile memory used to store data of certain variables
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3
...
e
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Atmega16 is equipped with 1KB of internal SRAM
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·

3
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11 SPI:
Serial Peripheral Interface, SPI port is used in serial communication between two devices with a
common clock source
...

3
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12 TWI:
Two Wire Interface (TWI) can be used to set up a network of devices, many devices can be
connected over TWI interface forming a network, the devices simultaneously transmit and receive
and having own unique address
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8

PIN DISCRIPTION

1
...

2
...

3
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Port A is an 8-bit bi-directional I/O port, if
A/D Converter is not used
...
When the pins PA0 to PA7 are used as the inputs and are
pulled low externally, they will source current if the internal pull-up resistors are activated
...
Port B
(PB7
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Port B
It is an 8-bit bi-directional I/O port having internal pull-up resistors (selected for each bit)
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As the inputs, Port B pins that are externally pulled low will source current if the pullup resistors are activated
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Port C (PC7
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The Port C output buffers symmetrically drive
characteristics having both high sink and source capability
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Port C

Pins as inputs that are externally pulled low will source current if the pull-up resistors are activated
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The TD0 pin is tri-stated until TAP states that the data shifted
out are entered
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Port D (PD7 - PD0)
Port D is an 8-bit bi-directional I/O port having internal pull-up resistors (selected for each bit)
...
As inputs, Port D pins that are externally pulled low will source the current if the pullup resistors are activated
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A low level on this pin for longer period than the minimum pulse length
will give a reset, even if the clock is not running
...
XTAL1
Is an input to the inverting Oscillator amplifier and input to the internal clock operating circuit
...

7
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It is generally externally
connected to VCC, if the ADC is not used
...
AREF Is the analog reference pin for the A/D Converter
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I/O PORTS
At mega 16 have 32 general purpose digital I/O pins
...
Let’s say we are talking about the pin PA0
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9
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3
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SENSORS
1
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2 LEVEL SENSOR
1
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POWER SUPPLY
3
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GSM MODULE
3
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The ADC is used to read the parameters,
built-in EEPROM is used to host the embedded software algorithm that takes care of the
parameters acquisition, processing, displaying, transmitting and receiving
...

The GSM modem is interfaced with the microcontroller through RS 232 adapter by which it
uploaded and download SMS messages that contain information related to the transformer
parameters and status
...
1 LCD (Liquid Crystal Display)
The display used is 16x2 LCD (Liquid Crystal Display); which means 16 characters per line by 2
lines
...
Here 8bit mode of LCD is used, i
...
, using 8-bit data bus
...

The EN line is called "Enable
...
For sending data to the LCD, the program should make sure that the line is low (0) and then
set the other two control lines or put data on the data bus
...

The RS line is "Register Select" line
...
When the RS is high (1), the data
sent is text data which is displayed on the screen
...

The RW line is "Read/Write" control line
...
When RW is high (1), the program is effectively questioning (reading) the

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LCD
...
All the others are write
commands--so RW will always be low
...
2

PIN DIAGRAM OF LEIQUID CRYSTAL DISPLAY UNIT

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4
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1 PIN DISCRIPTIONS

PIN NO
...
3 GSM MODEM
A GSM modem is a wireless modem that works with a GSM wireless network
...
The basic difference between them is the dial-up modem sends and
receives data through a fixed telephone line while the wireless modem sends and receives data
through waves
...

SIM 300 is a Fixed Cellular Terminal (FCT) used for data applications
...
It also can be connected to a
computer with a standard RS232C serial port
...
The SIM 300 is
very easy to set up
...


4
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SIM300 features GPRS multi
slot class10/ class8 and supports the GPRS coding schemes CS-i, CS-ii, CS-iii and CS iv
...
5 SIM card interface
We can use AT Command for getting information in SIM card
...

Both the 1
...
0V SIM Cards are supported
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8V
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4
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1 Operation
AT commands are used by the computers to control modems
...
GSM modem can be used like a dialup modem
...
These extended set of AT commands are defined in the GSM standards
...


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This GSM modem then sends this SMS to mobile users containing information about
parameters value of the distribution transformers
...
3 CIRCUIT DIAGRAM OF THE MODEL

6

set, GSM/GPRS modems and mobile phones also support an AT command sets which are specific
to the GSM technology, which also includes SMS-related commands
...
6
...

Basic commands are AT commands that do not start with "+"
...

Extended commands are AT commands that start with "+"
...
For example, +CMGS (Send SMS message), +CMSS (Send SMS message
from storage), +CMGL (List SMS messages) and +CMGR (Read SMS messages) are extended
commands
...
7 SERIAL COMMUNICATION
In our model serial communication from modem to microcontroller are done by connecting Txd
and Rxd pins to modem Rxd and Txd pin respectively
...

In our hardware architecture we have interface modem to microcontroller directly without the use
of Max232 or RS232 and having proper results with proper communication
...
They both can work in CMOS logic level or TTL logic level
...
But in our model both Microcontroller and GSM
Modem works in TTL logic level so here we have not used Max232 0r RS232
...


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CHAPTER 5

SOFTWARE IMPLEMENTATION
This chapter describes about the software implementation of the project
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5
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5
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The programming is done in embedded C language
...
This is the only language the
microcontroller will understand, because it has the original program code converted into a
hexadecimal format during this process some errors and warnings occurs
...
If not the whole procedure is repeated again
...
3 AVR STUDIO
AVR studio is software used where machine language code is written and compiled
...

The program is written in C language code
...
4 PRELOAD
Preload is software that accepts only hex files
...
Preload is a
programmer which contains a microcontroller in it other than the one which is to be programmed
...

The Preload programmer kit requires power supply to operate, this power supply is given by the
power supply circuit
...
This is accomplished from
the power supply board with an output of 12 V
...

program Loaded

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Hex file accepted and sent to MCU

CHAPTER 6
CONCLUSION
The gsm based monitoring of distribution transformer is quite useful as compared to manual
monitoring and also it is reliable as it is not possible to monitor always the oil level oil temperature
rise, ambient temperature rise load current manually
...
In a distribution network there are many distribution transformers and associating
each transformer with such system, we can easily figure out that which transformer is undergoing
fault from the message sent to mobile
...
The
time for receiving messages may vary due to the public GSM network traffic but still then it is
effective than manual monitoring
...
This database will be a useful source of information on the utility transformers
...


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REFERENCES
[1] Leibfried, T, “Online monitors keep transformers in service”, Computer Applications in

Power,

IEEE, Volume:11 Issue: 3 , July 1998 Page(s):36 -42
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L, So, A
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P
...
, L
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14, No
...
293-298
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Tenbohlen,T
...
Rösner,” Benefit of sensors for on-line monitoring systems for power
transformers”
[4] T
...
Poyser, "An On-Line Microprocessor Based Transformer Analysis System to

Improve the

Availability and Uti'lization of Power Transformers"
...
On Power Apparatus and Systems,
Volume PAS-102, April 1983, pp
...

[5] Muhammad Ali Mazidi , Janice Gillispie Mazidi, Rolin D
...

[6] Microcontroller ATmega 16; www
...
com/Images/doc2466
...

[7] Constantin Daniel Oancea,” GSM Infrastructure Used for Data Transmission”,

7th International

Symposium on Advanced Topics in Electrical Engineering (ATEE), 2011 May 12-14, Page(s): 1 – 4
...


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