“Microcontroller Based Substation Monitoring system with gsm modem”.

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CHAPTER 1: INTRODUCTION
1.1 Introduction
Substation monitoring and control using GSM modem presents an automotive
localization system using GSM-SMS services. The system is used for transmitting the
message to predefined number about the status of electrical parameters such as voltage,
current, temperature etc., to improve the quality of power.
Therefore it is necessary to be familiar with what sort of constraint has occurred .If
there is any inadequacy in the protection, monitoring and control of a power system then the
system might become unstable. Therefore there is a necessary for a monitoring system that is
able to automatically detect, monitor, and classify the existing constraints on electrical lines.
1.2 Objective of the project
The aim of this project is to acquire the remote electrical parameters like voltage,
current and frequency and send these real time values over GSM network using GSM
Modem/phone along with temperature at power station.
 To improve quality of power
 Remote sensing
 To Maintain Continuity of supply
 Real time monitoring

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CHAPTER 2: HARDWARE DISCRIPTION
2.1 Introduction of the Block diagram:
In this chapter the block diagram of the project and design aspect of independent
modules are considered. Block diagram is shown in figure.
BLOCK DIAGRAM:
Fig 2.1: Block Diagram

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The main blocks of this project are:
1. Micro controller (PIC16F877A)
2. Regulated power supply (RPS)
3. LED Indicator
4. G.S.M
5. Relay
6. Current transformer
7. Voltage sensor
2.2 MICROCONTROLLER:
Fig 2.2: Microcontroller
Microcontroller is a programmable device. A microcontroller has a CPU in addition
to a fixed amount of RAM, ROM, I/O ports and a timer embedded all on a single chip. The
fixed amount of on-chip ROM, RAM and number of I/O ports in microcontrollers makes
them ideal for many applications in which cost and space are critical.
The microcontroller used in this project is PIC16F877A. The PIC families of
microcontrollers are developed by Microchip Technology Inc. Currently they are some of the
most popular microcontrollers, selling over 120 million devices each year. There are basically
four families of PIC microcontrollers 16C6X, 16C7X, 16F87X.

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2.3 REGULATED POWER SUPPLY:
2.2.1 Introduction:
Power supply is a supply of electrical power. A device or system that
supplies electrical or other types of energy to an output load or group of loads is called
a power supply unit or PSU. The term is most commonly applied to electrical energy
supplies, less often to mechanical ones, and rarely to others.
A power supply may include primary or secondary sources of energy such as.
 Batteries.
 Chemical fuel cells and other forms of energy storage systems.
 Solar power.
 Generators or alternators.
Fig 2.3: Circuit diagram of Regulated Power Supply with Led connection
Transformers:
A transformer is a device that transfers electrical energy from one circuit to
another through inductively coupled conductors without changing its frequency. A
varying current in the first or primary winding creates a varying magnetic flux in the
transformer's core, and thus a varying magnetic field through the secondary winding. This

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varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the
secondary winding. This effect is called mutual induction.
The input coil is called the PRIMARY WINDING, the output coil is the
SECONDARY WINDING. The Transformers of two types based on the turns ratio
K=
If the K>1 Step down Transformer
If the K<1 Step up Transformer
Step down transformer:
In case of step down transformer, Primary winding induces more flux than the
secondary winding, and secondary winding is having less number of turns because of that it
accepts less number of flux, and releases less amount of voltage.
Fig 2.4: step up transformer
Rectifier:
A rectifier is an electrical device that converts alternating current (AC) to direct
current (DC), a process known as rectification. Rectifiers have many uses including as
components of power supplies and as detectors of radio signals. Rectifiers may be made of
solid-state diodes, vacuum tube diodes, mercury arc valves, and other components.

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Rectifiers are of two types:
1. Half wave Rectifier
2. Full wave Rectifier
I. Full wave Bridge Rectifier
II. Full wave center tapped Rectifier
Full wave Bridge rectifier: The Bridge rectifier circuit is shown in fig: 2.5, which converts
an ac voltage to dc voltage using both half cycles of the input ac voltage. The Bridge rectifier
circuit is shown in the figure. The circuit has four diodes connected to form a bridge. The ac
input voltage is applied to the diagonally opposite ends of the bridge. The load resistance is
connected between the other two ends of the bridge.
Input Output
Fig 2.5: Bridge rectifier: a full-wave rectifier using 4 diodes
For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct,
whereas diodes D2 and D4 remain in the OFF state. The conducting diodes will be in series
with the load resistance RL and hence the load current flows through RL.
For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct
whereas, D1 and D3 remain OFF. The conducting diodes D2 and D4 will be in series with the
load resistance RL and hence the current flows through RL in the same direction as in the
previous half cycle. Thus a bi-directional wave is converted into a unidirectional wave.
Filter:
Electronic filters are electronic circuits, which perform signal-processing functions,
specifically to remove unwanted frequency components from the signal, to enhance wanted
ones.

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We have seen that the ripple content in the rectifier output of half wave rectifier is
121% or that of full-wave or bridge rectifier is 48% such high percentages of ripples is not
acceptable for most of the applications.
Ripples can be removed by one of the following methods of filtering:
a) A capacitor, in parallel to the load, provides an easier by-pass for the ripples voltage
through it due to low impedance. At ripple frequency and leave the d.c. to appears the
load.
b) An inductor, in series with the load, prevents the passage of the ripple current (due to
high impedance at ripple frequency) while allowing the d.c (due to the low resistance
to d.c)
Various combinations of capacitor and inductor, such as L-section filter, π –section filter,
multiple section filters etc. which make use of both the properties mentioned in (a) and (b)
above. Two cases of capacitor filter, one applied on half wave rectifier and another with full
wave rectifier.
Fig 2.6:electrolytic capacitor
Filtering is performed by a large value electrolytic capacitor connected across the DC
supply to act as a reservoir, supplying current to the output when the varying DC voltage
from the rectifier is falling. The capacitor charges quickly near the peak of the varying DC,
and then discharges as it supplies current to the output. Filtering significantly increases the
average DC voltage to almost the peak value (1.4*RMS value).

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To calculate the value of capacitor (C),
C=1/4* √3 *f*r*RI
Where,
f =supply frequency,
r=ripple factor,
RI=load resistance
In our circuit we are using 10 & 1000microfarads.
Voltage Regulator:
A voltage regulator (also called a ‘regulator’) with only three terminals appears to be
a simple device, but it is in fact a very complex integrated circuit. It converts a varying input
voltage into a constant ‘regulated’ output voltage.
The LM78XX series of voltage regulators are designed for positive input. For
applications requiring negative input, the LM79XX series is used. Using a pair of ‘voltage-
divider’ resistors can increase the output voltage of a regulator circuit.
It is not possible to obtain a voltage lower than the stated rating. You cannot
use a 12V regulator to make a 5V power supply. Voltage regulators are very robust. These
can withstand over-current draw due to short circuits and also over-heating. In both cases, the
regulator will cut off before any damage occurs. The only way to destroy a regulator is to
apply reverse voltage to its input. Reverse polarity destroys the regulator almost instantly.
Fig: 3.3.11 shows voltage regulator.
Fig 2.7: Voltage Regulator

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Resistors:
A resistor is a two-terminal electrical component that produces a voltage across its
terminals that is proportional to the electric current passing through it. Resistor applications
vary widely, from current limiting, heating, sensing, voltage drops, and feedback loops are a
few common examples. A resistor limits the amount of current that flows through a circuit
based on resistance of resistor. Electrical resistance is measured in ohms and can be
determined with the use of ohms law.
Ohms law:
One of the most fundamental equations used in electrical engineering is ohm’s law. It gives
relationship between voltage, current, and resistance. Resistor was directly proportional to
current through the resistor.
I=V/R
V = IR
R=V/I
Where V=voltage (volts),
I=current (amps),
R=resistance (ohms).
3.4. LED (Light Emitting Diode):
A light-emitting diode (LED) is a semiconductor light source. LED’s are used as
indicator lamps in many devices, and are increasingly used for lighting. Introduced as a
practical electronic component in 1962, early LED’s emitted low-intensity red light, but
modern versions are available across the visible, ultraviolet and infrared wavelengths, with
very high brightness. The internal structure and parts of a led are shown below.

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Fig 2.9: Inside a LED Fig 2.10: Parts of a LED
The structure of the LED light is completely different than that of the light
bulb. Amazingly, the LED has a simple and strong structure. The light-emitting
semiconductor material is what determines the LED's color. The LED is based on the
semiconductor diode.
2.5 Liquid crystal Display (LCD):
One of the most common devices attached to a micro controller is an LCD display. Some of
the most common LCD’s connected to the many microcontrollers are 16x2 and 20x2
displays. This means 16 characters per line by 2 lines and 20 characters per line by 2 lines,
respectively
2.5.1: LCD Pin diagram
:
Fig2.11:LCD pin diagram

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LCD consists of totally 14 pins but in the 14 pins we use only 7 pins. And the other
are left free. The used pins are 2, 3, 4,6,11,12,13,14 whereas 2,3 are combined and given to
the supply, the rest of the pins are connected to the microcontroller 34,35,36,37,38,39,40.
And the rest of the pins of the microcontroller are used for input output ports.
Schematic:
Fig 2.12: schematic diagram of LCD
2.5.2: Applications:
The applications of LCD are
 Medical equipment, PC external display
 Electronic test equipment, HMI operator interface
 Industrial machinery interface
 Serial terminal
 Advertising system
2.6 Global System for Mobile Communication (GSM):
Definition:
GSM, which stands for Global System for Mobile communications, reigns
(important) as the world’s most widely used cell phone technology. Cell phones use a cell

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phone service carrier’s GSM network by searching for cell phone towers in the nearby area.
Global system for mobile communication (GSM) is a globally accepted standard for digital
cellular communication.
GSM is the name of a standardization group established in 1982 to create a common
European mobile telephone standard that would formulate specifications for a pan-European
mobile cellular radio system operating at 900 MHz. It is estimated that many countries
outside of Europe will join the GSM partnership.
Fig 2.13: GSM module
MODEM SPECIFICATIONS:
The SIM300 is a complete Tri-band GSM solution in a compact plug-in module.
Featuring industry-standard interface, the SIM300 delivers GSM/GPRS900/1800/1900Mhz
performance for voice, SMS, data and Fax in a small form factor and with low power
consumption.
The leading features of SIM300 make it deal fir virtually unlimited application, such
as WLL applications (Fixed Cellular Terminal), M2M application, handheld devices and
much more.
1. Tri-band GSM/GPR S module with a size of 40x33x2.85
2. Customized MMI and keypad/LCD support
3. An embedded powerful TCP/IP protocol stack
4. Based upon mature and field proven platform, backed up by our support service, from
definition to design and production.

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General Features:
 Tri-band GSM/GPRS900/1800/1900Mhz
 GPRS multi-slot class 10
 GPRS mobile station class –B
 Dimensions: 40x33x2.85 mm
 Weight: 8gm
 7. Control via AT commands
 (GSM 07.07, 07.05 and SIMCOM enhanced AT commands)
 SIM application tool kit
 supply voltage range 3.5…….4.5 v
 Low power consumption
 Normal operation temperature: -20 ’C to +55 ‘C
 Restricted operation temperature : -20 ’C to -25 ‘C and +55 ’C to +70 ‘C
 storage temperature: -40 ‘C to +80 ‘C
Specifications for SMS via GSM/GPRS:
 Point to point MO and MT
 SMS cell broadcast
 Text and PDU mode
Compatibility:
At cellular command interface
Need of GSM:
The GSM study group aimed to provide the followings through the GSM:
 Improved spectrum efficiency.
 International roaming.
 Low-cost mobile sets and base stations (BS)
 High-quality speech

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 Compatibility with Integrated Services Digital Network (ISDN) and other telephone
company services
2.7 Relay:
Relay is an electromagnetic switch. . It consists of a coil of wire surrounding a
soft iron core, an iron yoke, which provides a low reluctance path for magnetic flux, a
movable iron armature, and a set, or sets, of contacts; two in the relay pictured. The
armature is hinged to the yoke and mechanically linked to a moving contact or
contacts.
When an electric current is passed through the coil, the resulting magnetic field
attracts the armature and the consequent movement of the movable contact or contacts
either makes or breaks a connection with a fixed contact.
Fig
2.14: Internal circuit diagram of Relay
2.8 Potentiometer:
A potentiometer (colloquially known as a "pot") is a three-terminal resistor with a
sliding contact that forms an adjustable voltage divider. If only two terminals are used (one
side and the wiper), it acts as a variable resistor or rheostat. Potentiometers are commonly
used to control electrical devices such as volume controls on audio equipment.
Potentiometers operated by a mechanism can be used as position transducers, for example, in
a joystick.
Potentiometers are rarely used to directly control significant power (more than a watt).
Instead they are used to adjust the level of analog signals (e.g. volume controls on audio
equipment), and as control inputs for electronic circuits. For example, a light dimmer uses a

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potentiometer to control the switching of a TRIAC and so indirectly control the brightness of
lamps.
Fig 2.15: potentiometer
2.9 Temperature Sensor:
The Temperature Sensor LM35 sensor series are precision integrated-circuit
temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade)
temperature.
LM 35: (TEMPERATURE /FIRE SENSOR)
The LM35 sensor series are precision integrated-circuit temperature sensors, whose
output voltage is linearly proportional to the Celsius (Centigrade) temperature.
To detect the heat produced during fire occurrence we use temperature sensor.
Fig 2.16: temperature sensor

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The Temperature Sensor LM35 sensor series are precision integrated-circuit
temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade)
temperature.
LM35 Sensor Specification:
The LM35 series are precision integrated-circuit LM35 temperature sensors, whose
output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35
sensor thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the
user is not required to subtract a large constant voltage from its output to obtain convenient
Centigrade scaling.
The LM35 sensor does not require any external calibration or trimming to provide
typical accuracies of ±¼°C at room temperature and ±¾°C over a full -55 to +150°C
temperature range. Low cost is assured by trimming and calibration at the wafer level. The
LM35's low output impedance, linear output, and precise inherent calibration make
interfacing to readout or control circuitry especially easy.
It can be used with single power supplies, or with plus and minus supplies. As it
draws only 60 µA from its supply, it has very low self-heating, less than 0.1°C in still air. The
LM35 is rated to operate over a -55° to +150°C temperature range, while the LM35C sensor
is rated for a -40° to +110°C range (-10° with improved accuracy). The LM35 series is
available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA,
and LM35D are also available in the plastic TO-92 transistor package. The LM35D sensor is
also available in an 8-lead surface mount small outline package and a plastic TO-220
package.

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CHAPTER 3: PROJECT DESCRIPTION
3.1 INTERNAL CIRCUIT DIAGRAM
In this chapter, schematic diagram and interfacing of PIC16F877A
microcontroller with each module is considered
Fig3.1 Internal circuit diagram

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The schematic diagram of Substation monitoring and control system using GSM
modem explains the interfacing section of each component with micro controller, GSM
module and sensors.
All the hardware components are connected to the microcontroller. The crystal
oscillator is connected to 7th and 9th pins. The regulated power supply is connected to the 20th
pin, the 2nd, 3rd, and 6th pins are connected to the voltage sensor, temperature sensors, current
sensor respectively. The load is connected to the pin no. 21 to 28, reset button for
microcontroller is connected to the 1st pin, LED and relay are connected to the 13th and 15th
pins respectively. The GSM modem is connected to the 17th and 18th pins, 8th and 19th pins
are connected to the ground. All these components are integrated on the PCB and made as a
proteus hardware kit.
3.2 Working:
The voltage sensor, current sensor and temperature sensor and step up transformer are
directly connected to one of the input ports of the microcontroller. The LCD display is
connected in the input port of the microcontroller.
The GSM transmitting section and the load variation control are connected to the one
of the output ports in the microcontroller. The monitoring PC is connected to the main
station. The microcontroller at the substation monitors and captures the current, voltage and
temperature values for a period interval.
The captured values are stored in the data register of microcontroller and displayed
using the LCD display. The monitored voltage, current and temperature values of the
transformer are transmitted using the GSM. Based on the received information, controlling
operation is performed.
The rated values are given in the program that is rated voltage as 240v, rated current
as 12ampers, rated temperature as 45degrees.
If these parameters exceeded then the threshold level, the mobile receives the message
as transformer parameters which are greater than the fixed threshold level, then immediately
the unit is shutdown so as to protect.

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Fig 3.2 Snapshot of this Module

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3.3 Case study:
The project is performed on three various cases like high voltage, high current and high
temperature. The results are as follow
Case 1: Rated value of voltage is 240 volts
Fig 3.2: High voltage sending sms
Application of voltage more than 240 volts, load will be off using relay and line men receive
the message of high voltage alert through GSM.
Case 2: Rated value of current is 12 amps
Fig 3.3: High current sending sms

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Application of current more than 12 amps, load will be off using relay and line men receive
the message of high current alert through GSM.
Case 3: Rated temperature is 45degrees
Fig 3.4: High temperature sending sms
Application of temperature more than 45 degrees, load will be off using relay and a line man
receives the message of high temperature alert through GSM.

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CHAPTER 4: ADVANTAGES AND DISADVANTAGES
4.1 Advantages
The advantages of the project substation monitoring and control with GSM modes are
1. GSM based user-friendly interfacing.
2. Low power consumption.
3. Controls high and low voltage devices.
4. Long life.
5. GSM message alert.
6. Fast response.
7. Efficient and low cost design.
8. Low power consumption.
4.2 Disadvantages
The disadvantages of the project substation monitoring and control with GSM modes are
1. GSM interfacing is sensitive.
2. Depends upon the signal for communication.
4.3 Applications
The main applications of the project substation monitoring and control with GSM modes are
1. It can be used in places where humans cannot work.
2. Mainly in military applications, robots play a vital role for detection of explosives.
3. Can be used to control devices.

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CHAPTER 5: CONCLUSION
5.1 Conclusion:
The parameters voltage, current, temperature and frequency in a substation are
successfully monitored and controlled using GSM modem.
Integrating features of all the hardware components used have been developed in it.
Presence of every module has been reasoned out and placed carefully, thus contributing to the
best working of the unit. Secondly, using highly advanced IC’s with the help of growing
technology, the project has been successfully implemented. Thus the project has been
successfully designed and tested.
5.2 Future Scope:
By connecting temperature, gas, sensors to the system we can get the temperature of
dangerous zones in through message itself instead of sending human to there and facing
problems at field. The project can be extended by using relay which can be operated
automatically depending upon the inputs of sensors

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Bibliography
1. Jyotishman Pathak, Yuan Li, Vasant “A Service-Oriented Architecture for electric
Power Transmission System Asset Management", In ICSOC Workshops.
2. B. A. Carreras, V. E. Lynch "Blackout Mitigation Assessment in Power Transmission
Systems", Hawaii International Conference on System Science, January 2003.
3. Microcontrollers Architecture, Programming, Interfacing and System Design – Raj
Kamal
4. PIC Microcontroller Manual – Microchip
5. Zhi-Hua Zhou, Yuan Jiang, Xu-Ri Yin, and Shi-Fu Chen, "The Application of
Visualization and Neural Network Techniques in a Power Transformer Condition
Monitoring System", In: T. Hendtlass and M. Ali eds. Lecture Notes in Artificial
Intelligence 2358, Berlin: Springer- Vela.
6. M. Kezunovic, Y. Guan, M.Ghavami, “New concept and solution for monitoring and
control system for the 21st century substation”(IEEE)

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