Essay: Global System For Mobile Communication Modem (Gsm) Based Condition Monitoring Of Transformer

This project presents design and implementation of a mobile embedded system to monitor and record key operation parameter of a Transformer (125VA) such as overvoltage, overload,increase in winding temperature, rise or fall of oil level. It is about the design of the mobile embedded system where there exits communication between system and operator. For this we are using Transformer, microcontroller, logic level converter and GSM (global system for mobile communication modem). This GSM modem helps to monitor transformer health by sending message to the system. To reduce the risk of unexpected failure and the ensuring unscheduled outage, on-line monitoring is done to assess continuously the condition of the transformer. Also it is important to keep an eye on transformer health when operator is not present actually at transformer site so we are introducing system named as two way communication systems, where there exists communication between transformer and operator through GSM modem, where person can know any related parameter value of transformer health by sending message to the system. This system can be designed to send SMS alerts whenever related parameter value exceeds the predefined limits. This mobile system will help the transformer to operate smoothly and identify problem before any catastrophic failure

LITERATURE REVIEW

1) A compact Remote Monitoring System for a Three-Phase 10-kVA Energy-Efficient Switchable Distribution Transformer.
In this this paper a designed embedded system and embedded Ethernet have been implemented to achieve a compact remote condition monitoring for the of a 3 phase 10-KVA transformer. The embedded system performs acquisition of voltages, currents, and temperatures, controls the switching devices that connect the tappings of the transformer, and processes the acquired data.

2) Development of Condition Monitoring Instrumentation forSensing Power Transformers
In this paper the objective is to design and develop Data Acquisition and Storage parts of a measurement system that will be used for the Condition Monitoring (CM) of Power Transformers. The data captured from the sensors and stored in a database will be used by an application that will predict the behavior of the Power Transformer.

3) A new online method based on Leakage Flux Analysis for the Early Detection and Location of Insulating Failures in Power Transformers: Application to Remote Condition Monitoring
This paper present online analysis of transformer leakage flux as an efficient alternative procedure for assessing machine integrity and detecting the presence of insulating failures during their earliest stages. Very cheap and simple sensors, based on air-core coils, were built in order to measure the leakage flux of the transformer, and nondestructive tests were also applied to the machine in order to analyze pre and post failure voltages induced in the coils.

4) Condition Monitoring of Power Transformers using DGA and Fuzzy Logic
In this paper the previous result obtained from the neural network using the DGA results is applied to achieve the initial conclusion first .Then the fuzzy technique is used for detail diagnosis. By using this technique the result obtained from the fuzzy logic will have a higher accuracy.

5) Neuro Fuzzy System Based Condition Monitoring of Power Transformer
This paper will focus assuming that data have already been preprocessed The learning phase is essentially a search, in a space of possible model configurations, of the model that best represents the power transformer testing values. This method can be used for the various inputs and one output, strictly depends on the number of membership functions and their rule base and the type of the defuzzification method used.

6) Transformer Monitoring by using Vibration Analysis
In this paper the use of a vibration model to be applied to transformer monitoring is proposed. The paper deals with the introduction of the comparative method of the state estimation of transformers using continuous monitoring of transformer vibration. Condition monitoring techniques are illustrated in this paper and then the transformer oil-tank vibration is investigated as a main technique for transformer condition monitoring.

7) Distribution Transformer Monitoring Using GPRS
In this paper A design based on PIC Microcontroller is developed for monitoring the key parameters of Distribution Transformer in a substation. An algorithm for monitoring the voltage, current and temperature is developed and programmed to the microcontroller. It is observed that the proposed system is effective in monitoring and displaying the data using wireless communication network.

8) An Efficient Monitoring of Substation Using Microcontroller Based monitoring system
In this Paper the objective is to monitor the electrical parameters continuously and hence to guard the burning of distribution transformer or power transformer due to the constraints such as overload, over temperature and input high voltage. If any of these values increases beyond the limit then the entire unit is shut down by the designed controlling unit.

9) GSM Based SCADA Monitoring And Control System Substation Equipment
This system can be designed to send SMS alerts whenever the Circuit Breaker trips or whenever the Voltage or Current exceeds the predefined limits. This project makes use of an onboard computer which is commonly termed as microcontroller. This on board computer can efficiently communicate with the different sensors being used. The controller is provided with some internal memory to hold the code.

CHAPTER 1

INTRODUCTION

1.1 GENERAL
In the expanding world the demand of electricity is increasing day by day. The power utilities are making continuous efforts to reduce the gap between supply and demand. The effect of various faults in power system leads to unplanned outages in power system, which makes the situation still worse. Transformers are the heart of power system. They are the key apparatus in power system. Any fault on transformer leads to unnecessary outages and huge loss to electric utility. For proper and reliable operation of power transformer, continuous condition monitoring is being required.

Transformer is a high efficient static electrical device used for power transfer from one voltage level to the other and plays the vital role in electrical transmission and distribution system. From the day of this equipment in service, different stresses like electrical, mechanical, chemical, and environmental factors affect the condition of the transformer. At the initial stage, degradation of insulation quality occurs slowly. But this deterioration multiplies in due course of time and leads to final failure of the transformer. So, to overcome this situation, continuous monitoring of the condition and preventive measures is required for correct maintenance of the transformer.

Distribution transformers have a long service life if they are operated under good and rated conditions. However, their life is significantly reduced if they are overloaded, resulting in unexpected failures and loss of supply to a large number of customers thus effecting system reliability. Overloading and ineffective cooling of transformers are the major causes of failure in distribution transformers. Distribution transformers are currently monitored manually where a person periodically visits a transformer site for maintenance and records parameter of importance. This type of monitoring cannot provide information about occasional overloads and overheating of transformer oil and windings. All these factors can significantly reduce transformer life. Our system is designed based upon online monitoring of key operational parameters of distribution transformers can provide useful information about the health of transformers which will help the utilities to optimally use their transformers and keep the asset in operation for a longer period.

This project presents the design and development of an automatic real time monitoring system consisting of PIC micro controller, sensors and GSM modem.

1.2 OBJECTIVE
The main objective of this project is to design an automatic real time monitoring system in the following steps:

To design the hardware
To develop the embedded software using embedded-C
To design the overall system
To test the key parameter of transformer like over voltage, output current, increase in winding temperature, rise or fall in oil level.

The proposed project is of effective remote monitoring system for a single phase transformer’, aims in monitoring the transformer from remote place using GSM. To maintain uninterrupted power supply and also to protect the transformer from faults, an automatic monitoring system is needed.

1.3 PRESENT SCENARIO OF TRANSFORMER MONITORING
At present the manual method of monitoring is adopted in which the person using analog meters will manually measure the oil level and winding temperature of the transformer in the interval gap of one hour (approx.)

1.4 NEED OF THE WORK
Transformers are a vital part of the transmission and distribution system. Monitoring transformers for problems before they occur can prevent faults that are costly to repair and result in a loss of service. Current systems can provide information about the state of a transformer, but are either offline or very expensive to implement. This report outlines a new approach that is based on using remote monitoring system of the transformer using PIC Microcontroller with help of GSM technology. Remote condition monitoring of transformers has already been widely known and implemented with various techniques. The monitoring is mostly carried out to reveal significant parameters that reflect conditions of transformers, such as increase or decrease in oil level, over voltages, over currents, and increase in winding temperatures. Also the GSM modem used is a two way communication device, so the mobile user can any time know the condition of the transformer parameter by simply sending message to the modem.

PROPOSED SYSTEM
The system hardware has four hardware modules as embedded system, GSM modem, Sensor, mobile users and GSM networks.
The embedded module is located at the transformer site. It is utilized to acquire process, display, transmit and receive the parameters to/from the GSM modem.
The second is the GSM module. It is the link between the embedded system and the public GSM network.

1.5.1 DEMERITS OF THE EXISTING SYSTEM
Time consuming.
Expensive
The monitoring system must be designed for long-time operation.
It does not provide information about the about occasional overloads and overheating of transformer oil and windings. All these factors can significantly reduce transformer life.

1.5.2 MERITS OF THE PROPOSED SYSTEM
The remote monitoring system for the transformer is however quite unique because it includes measurements of the key operating parameters of the transformer.
Moreover, the system is useful not only in monitoring the parameters of the transformer (such as voltages and currents) but also in controlling the switching devices and performing switching at appropriate timings.
Automatically monitors the transformer no manual work is needed.
It requires less power and space and it is portable
Maintains uninterrupted power supply.
Protect the transformer from faults. .
Remote monitoring is possible
The proposed system is cost effective and reliable.

CHAPTER 2
CONDITIONING MONITORING OF TRANSFORMER

2.1 NEED OF CONDITIONING MONITORING

Condition monitoring is the first step in the preventive/ predictive maintenance program, which extends life of equipments by avoiding catastrophic failures and forced outages.

Condition monitoring helps to For see any deterioration/ defects in the condition of the equipment.Facilitate corrective actions to be taken in advance to prevent the unplanned outages of the system.

Conditioning monitoring is a online type of monitoring which gives the information of the present parameters and condition in order to avoid any catastrophic failure. Electricity distribution is the final stage in the delivery of electricity from generating power plants to end users. The transmission system voltage is stepped-down to lower levels by distribution substation transformers.

The primary distribution system is that portion of the power network between the distribution substation and the utilization transformers. The primary distribution system consists of circuits, referred to as primary or distribution feeders, which originate at the secondary bus of the distribution substation. The distribution substation is usually the delivery point of electric power in large industrial or commercial applications.

Electricity is one of the basic needs of people in modern world. So it is very important to have high reliability, high efficiency and high service quality in a distribution system. In order to meet these facts, following areas should be improved in a distribution system
Confirmation of the presence of fault.
In time proactive decisions.
Reduction of unplanned outage.
Predictable and reliable maintenance schedule.
Prevention of catastrophic failure and destruction of peripheral equipment.
Reduction of maintenance cost.
Provision of obtaining quality control features.
Increment of the system stability.
Minimizes the severity of any damage and eliminates consequential repairs
Increase safe working environment.
Information for future plan, regarding up rating, and refurbishment of equipment.
Use of equipment for maximum economical efficiency. Managers and extends the life of equipment with efficient and cost effective maintenance.

2.2 Methods Used For Condition Monitoring
Initial days, the population of transformers and traffic of the transmission lines were very less. So, complexities in the electrical environments were also within the limit of control. But recent days, the interconnection complexity of transmission lines, and need of key transformers monitoring is necessary. The following methods at present are used for conditioning monitoring

Sr No. Methods/Techniques/
Tests Condition Monitoring Involvement
1 IR measurement and PI value Condition of the insulation
(Oil and solid)
2 Capacitance and tan??
Measurement Condition of the insulation
(Oil and solid)
3 Low voltage injection tests (Voltage Ratio,
Voltage Balance, Excite current, SC current etc Overall conditions of
Transformer core and winding
4 Dissolve Gas Analysis 1. Condition of insulation
2. Primary diagnosis of fault.
5 Laboratory Testing of In-service Oil (Water
content, Acidity, Inhabitation content,
Interfacial tension, Flash point, Pour Point,
Viscosity, Dielectric strength, sp. resistance Condition of Transformer oil.
6 Turns Ratio Test 1. Condition of windings
2.Condition of Tap Positions
7 Partial discharge measurement Condition of Insulation (Solid)
8 Polarization spectrum technique / Recovery voltage measurement (RVM) Moisture Trend analysis of
winding and paper insulation.
9 FRA (frequency Response Analysis) 1. Mechanical displacement of winding.
2. Dynamic response of winding.
10 DP measurement 1. Condition of Solid Insulation.
2. Residual life assessment

Table 2.2: Methods/technique for conditioning monitoring

2.3 TRANSFORMER FAULT ANALYSIS
2.3.1 Over load
Over current is the current flowing through the transformer resulting from faults on the power system. Fault currents that do not include ground are generally in excess of four times full-load current; fault currents that include ground can be below the full-load current depending on the system grounding method. Over current conditions are typically short in duration (less than two seconds) because protection relays usually operate to isolate the faults from the power system. Overload, by contrast, is current drawn by load, a load current in excess of the transformer name-plate rating. In summary, loading large power transformers beyond nameplate ratings can result in reduced dielectric integrity, thermal runaway condition (extreme case) of the contacts of the tap changer, and reduced mechanical strength in insulation of conductors and the transformer structure. Three factors, namely water, oxygen, and heat, determine the insulation life of a transformer. Filters and other oil preservation systems control the water and oxygen content in the insulation, but heat is essentially a function of the ambient temperature and the load current. Current increases the hottest-spot temperature (and the oil temperature), and there by decreases the insulation life span.[2]

2.3.2 Over Temperature
Excessive load current alone may not result in damage to the transformer if the absolute temperature of the windings and transformer oil remains within specified limits. Transformer ratings are based on a 24-hour average ambient temperature of 30??C (86??F). Due to over voltage and over current, temperature of oil increases which causes failure of insulation of transformer winding.

2.3.3 Over Excitation
The flux in the transformer core is directly proportional to the applied voltage and inversely proportional to the frequency. Over excitation can occur when the per-unit ratio of voltage to frequency (Volts/Hz) exceeds 1.05 p.u. at full load and 1.10 p.u. at no load. An increase in transformer terminal voltage or a decrease in frequency will result in an increase in the flux. Over excitation results in excess flux, which causes transformer heating and increases exciting current, noise, and vibration.

2.3.4 Oil Level Fault
Oil mainly used in transformer for two purposes one is for cooling of transformer and another use is for insulation purpose. When temperature of transformer goes high, oil level in trans-former tank decreases due to heating effect. For normal operation of transformer oil level should maintain at required level. If oil level decreases beyond required level, it affect cooling and insulation of the transformer.
CHAPTER 3
Design of Circuit for GSM based conditioning monitoring of Transformer

3.1 BLOCK DIAGRAM

Fig 3.1 Basic block diagram

3.2 CIRCUIT

Fig 3.2 Circuit Diagram for GSM based conditioning monitoring

3.2.1 Circuit diagram description
The proposed circuit diagram is used for monitoring of transformer parameter like voltage, current, oil level, temperature of the windings based on programming done in the embedded C and loaded on microcontroller. The monitored output will be display on a (LCD) display screen (size 16*2) and at the same time message will be sent to the mobile user whose is stored in the microcontroller programming. The outputs are compared with the reference value of the transformer which are already define in the programming and microcontroller is programmed in such a way when the output values exceed the rated values it displays it on the screen and there will be an alarm. The microcontroller is programmed in such a manner so as to continuously scan the transformer and update the parameters at a particular time interval.

A voltage regulator(IC 7805)is used to produce regulated 5V output which is given to the microcontroller since the microcontroller operates on 5V dc .The voltage from the transformer are step down by voltage transformer (230/12V) , the temperature of the winding are sensed by the temperature sensors (LM35). The ultra sonic oil level detector is used to detect the level of oil. These values are given to the analog input port of the PIC microcontroller. Which converts the analog signal to digital signals to be compatible with microcontroller and when any of the above condition exceed the rated value, there will be an alarm and corresponding fault values are indicated on the display screen and message is sent to corresponding mobile user about the fault condition.

To interface the microcontroller with the GSM module as both work on different logic.
Microcontroller works on TTL logic and GSM works on RS232 logic.MAX232 is used which can interpret both the logic. It is a dual driver and receiver. In between MAX232 and GSM module there is a (DB9) socket.

By knowing about the fault value/condition the operator can quickly repair the fault condition and avoid the catastrophic failure. So to avoid damaged to the transformer. Even the receiver can send the message to the GSM asking about the condition of different parameter and the GSM modem will reply to the condition of the transformer through MSG as it is a 2 way GSM modem.

This way to sending and receiving message based communication is easy and fast and is even reliable .It is also cost effective compared to other methods of online monitoring of transformer. As transformer is the most costly equipment of the power system so its online conditioning monitoring is very important in order to avoid large catastrophic failure and also to avoid large expenses that can be caused by replacing of the transformer.

3.3 PIC16F877A MICROCONTROLLER
This is one of the most advanced microcontrollers from Microchip. This controller is widely used for experimental and modern applications because of its low price, wide range of applications, high quality, and ease of availability. It is ideal for applications such as machine control applications, measurement devices, study purpose, and so on. The PIC 16F877 features all the components which modern microcontrollers normally have. The figure of a PIC16F877 chip is shown below.[1]

Fig 3.4(a) PIC16F877A

3.3.1 General features
(i) All single-cycle instructions except for program branches, which are two-cycle
(ii)Operating Speed: DC-20 MHZ clock input DC- 200 ns instruction cycle
(iii)Up to 8K x 14 words of Flash Program Memory, Up to 368 x 8 bytes of Data Memory (RAM), Up to 256 x 8 bytes of EEPROM Data Memory
(iv) Fully static design.
(v) Wide operating voltage range (2.0 ‘ 5.56) volts.
(vi) High sink/source current (25mA).
(vii) Commercial, industrial and extended temperature ranges.
(viii) Low power consumption
3.3.2 Special Features
100000 times erase/write cycle enhanced memory.
1000000 times erase/write cycle data EEPROM memory.
Self programmable under software control.
In circuit serial programming and in circuit debugging capability.
Single 5V,DC supply for circuit serial programming
WDT with its own RC oscillator for reliable operation.
Programmable code protection.
Power saving sleep modes.
Selectable oscillator options
3.3.3 PIN DIAGRAM
PIC 16F877A chip is available in different types of packages. According to the type of applications and usage. The pin diagram is shown in the figure.

3.3.4 PIN DISCRIPTION

VDD(11,32):
This is the pin where supply voltage is given to the microcontroller. It gets 5v
from the power circuit. Positive supply for logic and I/O pins.

Fig 3.4(b) Pin diagram of PIC16F877A

VSS(12,31):
This pin is used as a ground reference for logic and I/O pins.

MCLR/VPP(1):
Master Clear (Reset) input or programming voltage input.
This pin is used to reset the programming.

3.3.5 Block Diagram

Fig. Block Diagram of PIC16F877A

PORT A (2-7):
In this controller, ‘PORT A’ is only 6 bits wide (RA-0 to RA-5).These ports are used for analog inputs. It is a bi-directional input/output port.

PORT B (33-40):
In this Controller, ‘PORT B’ is only 8 bit wide (RB-0 to RB-7).These ports are used for input/ output interfacing. It is a bi-directional input/output port. These can also be used as parallel slave when interfacing to a microprocessor.

PORT C (15-18,23-26):
In this Controller, ‘PORT C’ is only 8 bit wide (RC-0 to RC-7).These ports are used for input/output interfacing. . It is a bi-directional input/output port.

PORT D (19-22,27-30):
In this Controller, ‘PORT D’ is only 8 bit wide (RD-0 to RD-7).These ports are used for input/output interfacing. It is a bi-directional input/output port. It provides digital input/output.

PORT E (8-10):
In this controller,’ PORT E’ is only 3 bit wide (RE-0 to RE-2).PORTE is a bidirectional I/O port. They are used for input/output interfacing and for digital input/output.

OSC1/CLKI(13):
This pin is used as an Oscillator crystal or external clock input.

OSC2/CLKO(14):
This pin is used as an Oscillator crystal or clock output.

3.4 Various component design , calculation and simulation in proteus
As it is very expensive to manufacture circuit for 100KVA transformer so control circuit for 125VA is manufactured and tested and based on this circuit design of GSM based conditioning monitoring circuit is done for 125VA transformer.
3.4.1 Power supply
Power supply for the microcontroller and other electronic equipment used in the
Project like GSM is common .Both these require 5V DC supply to get turned ON and also the voltage should be maintained at 5V, there should not be much deviation .So designing of the power supply is done taking into consideration this point.

A 5V regulated supply is taken as followed
Each of the blocks is described below:
Transformer – steps down high voltage AC mains to low voltage AC.
Rectifier – converts AC to DC, but the DC output is varying.
Smoothing – smoothes the DC from varying greatly to a small ripple.
Regulator – eliminates ripple by setting DC output to a fixed voltage.

3.4.2 TRANSFORMER
Transformer is the electrical device that converts one voltage to another with little loss of power. Transformers work only with AC. There are two types of transformers as Step-up and Step-down transformer. Step-up transformers steps up voltage, step-down transformers steps down voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains voltage to a safer low voltage. Here a step down transformer is used to get 12V AC from the supply i.e. 230V AC.

3.4.3 RECTIFIERS
A rectifier is a circuit that converts AC signals to DC. A rectifier circuit is made using diodes. There are two types of rectifier circuits as Half-wave rectifier and Full-wave rectifier depending upon the DC signal generated.

3.4.4 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. The diagram shows the unsmoothed varying DC and the smoothed DC. The capacitor charges quickly to the peak of the varying DC and then discharges as it supplies current to the output. Here the capacitor of 330uF is used as a smoothing circuit.

3.4.5 VOLTAGE REGULATION
Voltage regulators produce fixed DC output voltage from variable DC (a small amount of AC on it). Fixed output is obtained by connecting the voltage regulator at the output of the filtered DC. It can also be used in circuits to get low DC voltage from high DC voltage (for example we use 7805 to get 5V from 12V). Two types of voltage regulators are
1. fixed voltage regulators (78xx, 79xx)
2. Variable voltage regulators (LM317)

Fig Power supply circuit design
For getting this 5V supply first of all the mains voltage 230V is given to the step down transformer(230V/12V) which steps it down to 12V AC supply .Now as DC voltage is required for various electronic equipments in the model. So the bridge rectifier with four diodes is used as shown in the figure. Diodes used are standard IN4007. These diodes have current capacity of 1 Ampere and voltage drop of 0.6 volts when forward biased.
So the voltage across the capacitor will be
Vc = 12-0.6
= 11.4 V
Now the maximum voltage is 12 V and the minimum voltage supplied to the voltage regulator (LM 7805) is 8V so now the difference in voltage is
‘V= 12V- 8V
= 4 V
Maximum load current is 500mA as the transformer is of 125VA
q = Cv
dq/dt = C dv/dt
i = C 4V/8ms
C = (500mA*8ms)/4V
C =1000??F

The voltage obtained from the rectifier has ripples so it is to be filtered .so for filtering capacitor of rating 1000 ??F and 25 V is used. Voltage rating of the capacitor is kept high so that if any problem occurs in the circuit and full secondary voltage appears across the capacitor that also the capacitor won’t get damaged .After this capacitor the voltage regulator (LM 7805) is placed .so this voltage regulator does not allow the voltage to increase more than 5V even if the input to it is increased thus voltage across the microcontroller pin won’t increase more than 5V.Also as shown in the power supply circuit a yellow colour LED D1 is placed in series with the voltage regulator .The blinking of LED indicates that the voltage regulator is ON .Also the current capacity of LED is 2mA-3mA so a resistor is placed in series with the LED so that LED blow away.

3.5 Sensors
Sensors are installed on transformer site which reads and measures the physical quantity from the distribution transformer and then it converts it into the analog signal. These analog signals are given to the microcontroller. Sensors are used for sensing load current, load voltage, winding temperature and oil level.

Following general set-up of sensors for example is proposed for the use at a Distribution transformer:
‘ LM35 for temperature measurement
‘ PT for load voltage measurement (single phase)
‘ C.T to measure load current (single phase)
‘ Ultrasonic distance detector sensor for oil level measurement
It is fundamental to measure electrical quantities like voltage and current directly at the transformer.

Sr.No Parameter measured Sensor used
1 Input and output voltage of the transformer(125VA) Voltage transformer
2 Input and output current of the transformer(125VA) Current transformer
3 Winding Temperature
measurement Temperature sensor (LM35)
4 Oil level measurement Ultrasonic oil level sensor (HC-SR04)

Fig Circuit for Input /output voltage measurement of transformer

The circuit shown in the figure is used for measurement of input and output voltage of the transformer. The voltage measurement device PT (potential transformer) is used for measuring voltage. A PT of (230/12 V) is connected in parallel with the transformer (125VA)which is under test .so the same voltage of 230 is across the PT. now it steps down the voltage to 12V ,now this voltage is rectified using a bridge rectifier circuit consisting of four general purpose diode IN4007. These diodes have current capacity of 1 Ampere and voltage drop of 0.6 volts when forward biased.
The capacitor value is calculated same as above in the power supply circuit. The voltage obtained is 12 V dc .This voltage is to be given to the microcontroller, but input to the microcontroller should not increase more than 5V .so a voltage divider circuit is to be designed so that voltage does not increase more than 5V .Now 10k and 2k resistors each of 1 watt are placed in series with each other.
So voltage across resistor R1 is
R1 = (R2/(R1+R2))*V
= (2/12)*12
= 2V
Same way the voltage across the resistor R2 will be
R2 = (R1/(R1+R2))*V
= (10/12)*12
= 10V
So by using 10k preset voltage to the microcontroller pin can be adjusted.
Similarly the circuit for measuring output voltage is designed.

Fig. Circuit for Input /output current measurement of transformer

We are having a transformer of 125VA
So current I= P/V
= 125/230
= 0.5 A
which has nearly 500mA current which is very small and the CT to measure this current is not available in the market .so we use VT to measure the current .The secondary of the VT is connected in series with the transformer. A resistor of 10E is connected in parallel with secondary so that maximum current flows through the secondary winding now the VT used is of rating (230/12 V) i.e nearly 20 times.
Consider the maximum load of 100W
So P=VI
I=P/V
I= 0.4
=400mA
Now, V= IR
= 400*10
= 4V
Now the voltage on the primary will be 20 times so (20*4) it will be 80V. Now, this voltage is ac so it is converted into dc by the bridge rectifier. By using bridge rectifier consisting of four diodes AC voltage is converted into DC. Now this large voltage cannot be inputted directly to the pin of microcontroller so a voltage divider is used two resistor of R1=10k and R2=47k is used. Now the voltage across the resistor R1 is
R1 = (R2/(R1+R2))*V
=(47/57)*80
= 14.03 V
And across resistor R2 is
R2 = (R1/(R1+R2))*V
=(10/57)*80
= 65.96 V
and capacitor value is calculated similarly as calculated before and it will 220??F/200V.
Now here the resistor value is high so it take more time to give the result so a resistor of 10k is placed in parallel so the total resistance value will be minimum and so the time for the processing will be minimized.

3.5.3 Temperature sensor
The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 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.

Fig 3.9 Temperature sensor (LM35)

LM 35 is directly connected to the analog ports of the PIC Microcontroller (RA1).which directly give the temperature of the winding. As second connection of the temperature sensor is to the winding of the transformer.

Features
Calibrated directly in ?? Celsius (Centigrade)
Linear + 10.0 mV/??C scale factor
0.5??C accuracy guarantee able (at +25??C)
Rated for full ’55?? to +150??C range
Suitable for remote applications
Low cost due to wafer-level trimming
Operates from 4 to 30 volts
Less than 60 ??A current drain
Low self-heating.
Low impedance output
3.5.4 Ultrasonic oil level detector (HC-SR04)
Introduction:
Ultrasonic oil level sensor is used for oil level measurement in the transformer. When temperature of transformer goes high, oil level in transformer tank decreases due to heating effect. For normal operation of transformer oil level should maintain at required level. If oil level decreases beyond required level, it affect cooling and insulation of the transformer.

Fig. Ultrasonic distance detector(HC-SR04)

Here a ultrasonic oil level detector is used to measure the level of oil .which is placed at the top of the tank in which transformer of 125VA is placed .It is directly connected (RC7) port of the transformer. This sensor doesn’t require any analog port. so it is connected to port (RC7).It works on the principle of ultrasonic it consists of a transmitter and a receiver as shown in the figure. Transmitter sends the signals and if there is any obstacle in the path of the transmitter then the signal returns back to the receiver and in this way the level of oil is detected in transformer.

3.5.2 Application:
Fuel tank level sensor can measure changing level of any liquid (diesel, gasoline, water, liquefied gas, milk etc.) in moving and fixed tanks (vehicles fuel tanks, fuel tank tracks, railway tank cars, industrial tanks and liquid storages). The measurements are provided through the tank bottom so no damage and drilling of the tank are needed.

3.6 LCD (Liquid Crystal Display)

Fig. Circuit of LCD interfacing in Proteus

The display used is 16×2 LCD (Liquid Crystal Display); which means 16 characters per line by 2 lines.The standard is referred as HD44780U, which refers to the controller chip which receives data from an external source (Here Atmega16) and communicates directly with the LCD. Here 8-bit mode of LCD is used, i.e., using 8-bit data bus.
The three control lines are EN, RS, and RW.
The EN line is called "Enable." This control line is used for telling the LCD that we are sending data. 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. When the other lines are ready completely, bring EN high (1) and should wait for the minimum time required by the LCD datasheet and end by bringing it low (0) again.
The RS line is "Register Select" line. When RS is low (0), the data is treated as a command or special instruction (such as clear screen, position cursor, etc.). When the RS is high (1), the data sent is text data which is displayed on the screen. For example, to display the letter "B" on the screen you would set RS high.
The RW line is "Read/Write" control line. When RW is low (0), the information on the data bus is written to the LCD. When RW is high (1), the program is effectively questioning (or reading) the LCD. Only one instruction ("Get LCD status") is read command. All the others are write commands–so RW will always be low.
In case of an 8-bit data bus, the lines are referred to as DB0, DB1, DB2, DB3, DB4, DB5, DB6, and DB7.

Pin no Name Description
1 VSS GND
2 VCC Power supply(+5V)
3 VEE Contrast adjustment
4 RS 0= instruction input
1= data input
5 R/W 0 = write to LCD
1= read from LCD
6 EN Enable signal
7 D0 Bit 0 LSB
8 D1 Bit 1
9 D2 Bit 2
10 D3 Bit 3
11 D4 Bit 4
12 D5 Bit 5
13 D6 Bit 6
14 D7 Bit 7 MSB
3.7 GSM modem
3.7.1 Introduction
A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem is like a dial-up modem. 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. Like a GSM mobile phone, a GSM modem also requires a SIM card from a wireless carrier to operate. This GSM Modem can accept any GSM network operator SIM card and act just like a mobile phone with its own unique phone number. This modem has the advantage that you can use its RS232 port to communicate and develop embedded applications. Applications like SMS Control, data transfer, remote control and logging can be developed easily. The SIM 300 is very easy to set up. It also finds its applications in IT companies, Banks, Financial Institutions, Service Providers, Far away Project Sites, and other business establishments
With a tiny configuration of 40mm x 33mm x 2.85 mm, SIM300 can fit almost all the space requirement in your application, such as Smart phone, PDA phone and other mobile device. PIC microcontroller cannot be connected directly to modem. So MAX 232 is used to interface PIC and the modem
This GSM modem is a highly flexible plug and play tri band GSM modem for direct and easy integration to RS232 applications. Supports features like Voice, SMS, Data/Fax, GPRS and integrated TCP/IP stack.
3.7.2 Feature
Highly Reliable for 24×7 operation with Matched Antenna
Status of Modem Indicated by LED
Simple to Use & Low Cost
Tri Band Modem supports all GSM operator SIM cards

3.7.3 Application
Security Applications
Sensor Monitoring
GPRS Mode Remote Data Logging
SMS based Remote Control & Alerts
3.7.4 SIM card interface
We can use AT Command for getting information in SIM card. The SIM interface supports the operation of the GSM Phase 1 specification and also supports the operation of the new GSM Phase 2 and specification for FAST 64kbps SIM (intended to use having a SIM application Tool-kit). Both the 1.8V and 3.0V SIM Cards are supported. The SIM interface get its power from an internal regulator in the module having nominal voltage 2.8V. All the pins are reset as outputs driving low.
Operation: AT commands are used by the computers to control modems. Both the GSM modems and dial-up modems support a fixed set of standard AT commands. GSM modem can be used like a dial-up modem. Apart from the standard AT commands, GSM modems also support an extended set of AT commands. These extended set of AT commands are defined in the GSM standards. With the extended AT commands, several things are done:
‘ To read,write and delete SMS messages.
‘ To send SMS messages.
‘ To monitor the signal strength.
‘ To monitor the charging status and charge level of the battery
‘ Reading, writing and searching phone book entries.
The number of SMS messages processed by a GSM modem per minute is very low
only six to ten SMS messages per minute.
Network indication by red led on the GSM modem
If led off SIM 300 is not running.
64ms On/ 0.8 sec Off- SIM300 does not find the network
64ms On/ 3Sec off- SIM300 find the network

3.7.5 Instruction of GSM modem.
AT commands: AT commands are the instructions used for controlling a modem. AT stands for Attention. Each and every command line starts with "AT" or "at". Beacause of this modem commands are called AT commands. Many of the commands are also used for controlling wired dial-up modems. These are supported by GSM/GPRS modems and mobile phones. Apart from this common AT command 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.
Basic Commands and Extended Commands:
There are two types of AT commands: They are basic commands and extended commands.
Basic commands are AT commands that do not start with "+". For example, D (Dial), A (Answer), H (Hook control) and O (Return to online data state) are basic commands.
Extended commands are AT commands that start with "+". All GSM AT commands are extended commands. For example, +CMGS (Send SMS message), +CMSS (Send SMS message from storage), +CMGL (List SMS messages) and +CMGR (Read SMS messages) are extended commands
SERIAL COMMUNICATION

In the figure shown above there is a serial communication between the modem and microcontroller without the use of RS232 logic level converter.
Serial communication is done by connecting modem Txd and Rxd pin with microcontroller Txd and Rxd pin respectively.and third pin of modem is grounded.

3.8 MAX 232
In our model the RS232 is used to have serial communication between the microcontroller and Modem as both work on different logic .Microcontroller works on TTL logic and Modem works on CMOS logic so to have proper communication between them a logic level converter RS232 or MAX232 is used.RS232 is basically known as logic level converter.The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply RS-232 voltage levels from a single 5-V supply. Each receiver converts RS-232 inputs to 5-V TTL levels. Each driver converts TTL input levels into RS-232 levels.The RS232 level translator chip TTL to RS232 and RS232 to TTL.There is socket DB9 that is used to connect GSM modem with the MAX232 . It receives the TTL logic from the microcontroller and sends the RS232 logic to the GSM modem and also vice versa.
This converter can be used on any Microcontroller – PIC, Atmel or other which has TTL serial communications that needs to be converted to RS232 logic.

3.8.1 FEATURES
Input voltage levels are compatible with standard TTL levels
Output voltage levels are compatible with RS-232 E levels
Single Supply voltage: 5V
Low input current: 0.1??A at ??A= 25 ‘?
Output current: 24mA

3.8.2 PIN DAIGRAM OF MAX232

Fig 3.12 Pin Diagram of MAX232
3.8.3 PIN DESCRIPTION

No. Name Function
1 C1+ External capacitance of positive voltage multiplier unit
2 V+ Output of positive voltage of multiplier unit
3 C1- External capacitance of positive voltage multiplier unit
4 C2+ External capacitance of negative voltage multiplier unit
5 C2- External capacitance of negative voltage multiplier unit
6 V- Output of negative voltage of multiplier unit
7 TR2OUT Output of transmitter data (levels RS ‘ 232)
8 RE2IN Input of receiver data (levels RS ‘ 232)
9 RE2OUT Output of receiver data (levels TTL/CMOS)
10 TR1IN Input of transmitter data (levels TTL/CMOS)
11 TR2IN Input of transmitter data (levels TTL/CMOS)
12 RE1OUT Output of receiver data (levels TTL/CMOS)
13 RE1IN Input of receiver data (levels RS ‘ 232)
14 TR1OUT Output of transmitter data (levels RS ‘ 232)
15 GND Ground
16 VCC Supply voltage

Table 3.12:-Pin description of MAX232
)
Fig. control card (PCB)
PCB consists of PIC microcontroller (PIC 16F877A), LCD ,resistors ,electrolytic and ceramic capacitors, crystals,MAX232 , DB9 socket and buzzer used in this PCB are standard as suggested by the manufacture and so no particular design is required .LCD used is 16*2 type . A 5k’ pot is used for adjusting the brightness of the LCD and a ceramic capacitor of 0.1 ??F are used for minimizing the noise signal. A DB9 socket is used for connecting GSM modem with MAX232 for serial communication.

Vcc
It is a pin of microcontroller where supply voltage is given .It gets 5V from the power circuit.
GND
Ground
Port A (RA0-RA5)
Pin RA0 is connected to measure the input voltage of the transformer.
Pin RA1 is connected to measure the winding temperature of the transformer.
Pin RA5 is connected to measure the output current of the transformer.
Pin RA6 is connected to measure the output voltage of the transformer.
Pin RA7 is connected to measure the input current of the transformer.
Port B (RB0-RB7)
Pin RB0-RB7 are connected to the LCD pin .
Port C(RC0-RC7)
Pin RC6 is used for transmission of data from the microcontroller.
Pin RC7 is used for receiving data to the microcontroller.
Port D(RD0-RD7)
Pin RD0 is connected to the buzzer.
Pin RD1 is connected to the Input Relay.
Pin RD2 is connected to the Output Relay.
Pin RD3 is connected to the RS pin of the LCD.
Pin RD4 is connected to the RW pin of the LCD.
Pin RD5 is connected to the EN pin of the LCD.
Pin RD6 is connected to the Oil Sensor Relay.
OSC1-OSC2
A crystal of frequency of 11.0592 Hz is used with two capacitor each of 22??F connected to the pin 13 and pin 14 of the PIC Microcontroller.
MCLR
A master clear reset pin is used to start the program from the beginning and it is connected to the pin 1 of the PIC Microcontroller.

CHAPTER 4
Total Cost for the Design of the Model

Fig. Model of GSM based condition monitoring of Transformer

Fig. GSM modem

Sr. No. Equipment
Quantity Cost(Rs)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30 125VA ,230-0-230 V
PIC16F877A
Control card (PCB)
General PCB
LCD
Resistors 1k
Trim POT resistor of 10K
Capacitor 1000uF ,25V
Capacitor 10uF ,40V
Capacitor 0.1uF
Capacitor 220uF ,200V
Resistors 10E/10W
LED
IC MAX232
LM 7805
Relay 12V DC
Crystal
Step-down transformer 12-0/500mA
Buzzer
Temperature sensor (LM 35)
Ultrasonic distance detector (HC-SR04)
DB9 socket
Push button
Rectifier diode
Supply jack
GSM MODEM (SIM 300)
Adapter 12V DC,2 A
Transistor (BC547)
Bridge rectifier
Resistor 10E/5W

01
01
01
01
01
20
05
03
11
16
02
04
03
01
01
03
01
04
01
01
01
01
02
06
01
01
01
05
04
02 1000
150
150
60
175
10
25
15
22
08
10
02
06
20
10
90
06
280
22
50
1000
10
04
09
10
1800
150
7.5
88
20
TOTAL 5185.5

Algorithm
The step by step procedure for monitoring and controlling the transformer parameter like overvoltage, overload, temperature rise and rise and fall in oil level are explained as follows

Step 1: Start
Step 2: Check the connection
Step 3: Verify the destination number on which message is to be received about the abnormal condition of the parameter.
Step 4: Verify the hardware for the power supply; 5V dc is given to microcontroller and GSM modem and 230 V mains to the transformer (125VA)
Step 5: Input the reference maximum and minimum value for the various transformer parameters like input and output voltage , input and output current, increase or decrease in oil level and increase in temperature.
Step 6: Transfer the value of potential transformer, current transformer and temperature sensor to the ADC port.
Step 7: If the input or output voltage value is more than 250V, then the indication is ‘input voltage is high’ or ‘output voltage is high’.
Step 8: If the input or output voltage value is less than 150V, then the indication is ‘input voltage is low’ or ‘output voltage is low’.
Step 9: If the input or output current is more than 250mA, then the indication is ‘input current is high’ or ‘output current is high’.
Step 10: If the value for oil level is more than 30 cm then the indication is ‘oil level minimum’ or if it is less than 20 cm then the indication is ‘oil level is maximum’. (Distance is measured from the oil sensor which is mounted at the top of the tank so as the distance of oil in the tank from the oil sensor increases it indicates ‘oil level minimum ‘ and vice versa)
Step 11: If the value for the temperature is more than 70??C, then the indication is ‘Temperature is high’.
Step 12: This values are first compared with reference value, if any of the parameter violates the relay trips and also alarm operates
Step 13: The GSM modem is initialized with AT commands so if any of the parameter condition of the transformer exceed above reference value, message is received by the mobile user.
Step 14: After any abnormal condition as the relay trips, the microcontroller will not scan the other parameter unless the previous condition is brought to normal condition. As the pin is reset, the scanning of parameter will being from the starting
Step 14: A particular password is set for knowing the condition of the transformer parameter by the mobile user, he can just use the password assigned and can know the parameter condition.
Step 15: Stop

Fig. Flowchart
Program
Now, as the circuit is microcontroller based so some programming language is to be written so that the microcontroller can understand and can work according to the language of the programming.
The following program is written in C language and executed in MPLAB IDE software and the loader used is PICkit2.

#include <pic16F877A.h>
const unsigned char command1[10] = "at+cmgf=1";
const unsigned char command2[18]="at+cnmi=1,2,0,0,0";
const unsigned char send_sms_command[9]="AT+CMGS=";
const unsigned char destination[14]="+918866686188";
void delay(unsigned int millisec);
void inputting();
unsigned char n;
unsigned char chNum = 0,ch=0;
unsigned char chl_count,transformer_data[8];
// transformer data[0] = input voltage
// transformer data[1] = temperature
// transformer data[2] = oil level
// transformer data[3] = input current
// transformer data[4] = output current
// transformer data[5] = output voltage
// transformer data[6] = spare
// transformer data[7] = spare
const unsigned char line1[17] = "GsmBaseCondition";
const unsigned char line2[17] = " monitoring of ";
const unsigned char line3[17] = "Power Transformer";
const unsigned char line4[17] = "By MonikaAgarwal";
const unsigned char display[6][17] = {"ipVoltage = ", //AN0
"temperature = ", // AN1
"oil level = ", // no adc required
"ip current = ", // AN7
"op current = ", // AN5
"opVoltage = "}; // AN6
const unsigned char high alarm[6][17] = {"ip Voltage high ",
"temperature high",
"oilLevel minimum",
"ip current high ",
"op current high ",
"op Voltage high "};
const unsigned char low_alarm[6][17] = {"ip Voltage low ",
"temperature low ",
"oilLevel maximum",
"ip current low ",
"op current low ",
"op Voltage low "};
#define IP_VOLTAGE_HIGH 0
#define TEMPERATURE_HIGH 1
#define LEAKAGE_HIGH 2
#define IP_CURRENT_HIGH 3
#define OP_CURRENT_HIGH 4
#define OP_VOLTAGE_LOW 5
#define ALL_OK 6
unsigned char transformer_condition;
#define IPV_HIGH_LIMIT 250
#define TEM_HIGH_LIMIT 70
#define OIL_GAP_MAX 30 // minimum oil in transformer housing
#define IPC_HIGH_LIMIT 250
#define OPC_HIGH_LIMIT 250
#define OPV_HIGH_LIMIT 250
#define IPV_LOW_LIMIT 150
#define TEM_LOW_LIMIT 0
#define OIL_GAP_MIN 20 // maximum oil in transformer housing
#define IPC_LOW_LIMIT 0
#define OPC_LOW_LIMIT 0
#define OPV_LOW_LIMIT 150
unsigned int upper_limit[6]=
{IPV_HIGH_LIMIT,TEM_HIGH_LIMIT,OIL_GAP_MAX,IPC_HIGH_LIMIT,OPC_HIGH_LIMIT,OPV_HIGH_LIMIT};
unsigned char lower_limit[6]=
{IPV_LOW_LIMIT,TEM_LOW_LIMIT,OIL_GAP_MIN,IPC_LOW_LIMIT,OPC_LOW_LIMIT,OPV_LOW_LIMIT};
void lcdcmd (unsigned char value); // lcd command
void lcddata (unsigned char value); // lcd data
void MSDelay (unsigned int i);
#define rs RD3
#define rw RD4
#define en RD5
#define LCD PORTB
#define BUZZER RD0
#define INPUT_RELAY RD1
#define OUTPUT_RELAY RD2
#define SENSOR_RELAY RD6
#define ON 1
#define OFF 0
unsigned char distance_buffer[8];
unsigned char messege_buffer[16];
unsigned char char_counter,incorrect_char_received;
const unsigned char password[]= "*50641STATUS@";

unsigned char transmit_buffer[]="IPV=xyz:Tmp=xyz:Oil=xyz:IPC=xyz:OPC=xyz:OPV=xyz";
bit password_correct;
unsigned char commanded_device_no;
bit device_no_info_recieved;
bit message_started,message_ended;
bit request;
unsigned char temp,loop,oi_level;
#define YES 1
#define NO 0
#define PENDING 1
#define CLEARED 0
#define NONZERO 9
unsigned char Hum, Temp,debug; //8 bit variables
void interrupt receive(void)
{
if(RCIF == 1)
{ temp = RCREG;
if(temp == ‘*’)
{
message_started = YES;
}
if( message_started == YES )
{
messege_buffer[char_counter] = RCREG;
char_counter++;
}
if( temp == ‘@’)
{
message_ended = YES;
}}}
void main(void)
{
unsigned char i,hund,tens,unit,temp;
// start of PORTA pin programming
// spare RA4
TRISA0 = 1; // AN0 ip
TRISA1 = 1; // AN1 ip
TRISA2 = 1; // AN2 ip
TRISA3 = 1; // AN3 ref ip
TRISA5 = 1; // AN4 ip
// end of PORTA pin programming
// start of PORTB pin programming
TRISB = 0; // LCD dat op
// end of PORTB pin programming
// start of PORTD pin programming
TRISD = 0; // PORTD all op for LCD controls and relay and buzzer
// RD6, RD7 spare
PSPMODE = 0; //
// PSPMODE: Parallel Slave Port Mode Select bit
// 1 = PORTD functions in Parallel Slave Port mode
// 0 = PORTD functions in general purpose I/O mode
// end of PORTD pin programming
// start of PORTE pin programming
TRISE0 = 1; // analog ip AN5
TRISE1 = 1; // analog ip AN6
TRISE2 = 1; // analog ip AN7
// end of PORTE pin programming
// start of pin programming for ANx
PCFG0 = 1; // analog ref in on AN3,and all other are analog ips
PCFG1 = 0; // do
PCFG2 = 0;// do
PCFG3 = 0;// do
//0001 A A A A VREF+ A A A AN3 VSS 7/1
// end of pin programming for ANx
INPUT_RELAY = OFF;
OUTPUT_RELAY = OFF;
SENSOR_RELAY = 1;
BUZZER = OFF;
// ******************** start of setting serial comm with baud rates 9600
//(Asynchronous) Baud Rate = FOSC/(64 (X + 1))
// X = value in SPBRG (0 to 255)
// 9600 = 11059200/(64(x + 1))
// x + 1 = 11059200/9600 = (110592/96)/64 = 18
// x = 18 – 1
// x = 17
// SPBRG = 17
SPBRG = 17;
TX9 = 0; // 8 bit transmission
TXEN = 1;// transmission enabled
SYNC = 0; // asynchronous mode
BRGH = 0; // low speed
SPEN = 1; // serial port enabled
RX9 = 0; // 8 bit reception
CREN = 0; // if on rx interrupt -> initially continuous reception disabled,enabled before reception
// ******************** end of setting serial comm with baud rates 9600
//************* start of initialisation codes of GSM ************************************
for(i=0; i<9; i++)
{
TXREG = command1[i];
MSDelay(10);
}
for(i=0; i<17; i++)
{
TXREG = command2[i];
MSDelay(10);
}
MSDelay(1000);// waiting for OK signal
//************* end of initialisation codes of GSM **************************************
lcdcmd(0x38); // 2 line & 5*7 matrix
MSDelay(1);
lcdcmd(0x0C); // display on cursor off
MSDelay(1);
lcdcmd(0x01); //Clear display
MSDelay(1);
lcdcmd(0x80); // line 1, position 0
MSDelay(1);
for(i =0; i<16; i++)
{
lcddata(line1[i]);
MSDelay(1);
}
lcdcmd(0xC0); // line 2, position 0
MSDelay(1);
for(i =0; i<16; i++)
{
lcddata(line2[i]);
MSDelay(1);
}
MSDelay(5000);
lcdcmd(0x80); // line 1, position 0
MSDelay(1);
for(i =0; i<16; i++)
{
lcddata(line3[i]);
MSDelay(1);
}
lcdcmd(0xC0); // line 2, position 0
MSDelay(1);
for(i =0; i<16; i++)
{
lcddata(line4[i]);
MSDelay(1);
}
MSDelay(5000);
INPUT_RELAY = ON;
OUTPUT_RELAY = ON;
BUZZER = OFF;
message_started = NO;
message_ended = NO;
loop = 0;
char_counter = 0;
request = CLEARED;
while(1)
{
if( message_ended == YES )
{
incorrect_char_received = 0;
for(loop = 0; loop < char_counter-2; loop++)
{
lcddata(messege_buffer[loop]);
MSDelay(10);
if(password[loop] != messege_buffer[loop] )
incorrect_char_received++;
}}
if(password_correct == YES && request == PENDING)
{
for(i=0; i<8; i++)
{
TXREG = send_sms_command[i];
MSDelay(10);
}
for(i=0; i<13; i++)
{
TXREG = destination[i];
MSDelay(10);
}
for(i=0; i<47; i++)
{
TXREG = transmit_buffer[i];
MSDelay(10);
request = CLEARED;
password_correct = NO;
}
for(chl_count=0; chl_count<6; chl_count++)
{
inputting();
hund = transformer_data[chl_count]/100;
temp = transformer_data[chl_count]%100;
tens = temp / 10;
unit = temp % 10;
//unsigned char transmit_buffer[]="IPV=xyz:Tmp=xyz:Oil=xyz:IPC=xyz:OPC=xyz:OPV=xyz";
transmit_buffer[chl_count*8+4]= hund + ‘0’;
transmit_buffer[chl_count*8+5]= tens + ‘0’;
transmit_buffer[chl_count*8+6]= unit + ‘0’;
lcdcmd(0x01); //Clear display
MSDelay(1);
lcdcmd(0x80); // line 1, position 0
MSDelay(1);
for(i =0; i<16; i++)
{
lcddata(display[chl_count][i]);
MSDelay(1);
}
lcdcmd(0x8D); // line 1, position 0
MSDelay(1);
lcddata(hund + ‘0’);
MSDelay(1);
lcddata(tens + ‘0’);
MSDelay(1);
lcddata(unit + ‘0’);
MSDelay(1);
lcdcmd(0xC0); // line 1, position 0
MSDelay(1);
lcddata(chl_count +’0′);
delay(1000);
// MONITORING parameters for 10 times
if((transformer_data[chl_count] > upper_limit[chl_count])||(transformer_data[chl_count] < lower_limit[chl_count]))
{ // startof if(1)
for(i=0;i<10;i++)
{
inputting();
if((transformer_data[chl_count] > upper_limit[chl_count])||(transformer_data[chl_count] < lower_limit[chl_count]))
MSDelay(1000);
else
break;
}
if(i==10)
{
if(transformer_data[chl_count] > upper_limit[chl_count])
{
lcdcmd(0x01); //Clear display
MSDelay(1);
lcdcmd(0x80); // line 1, position 0
MSDelay(1);
for(i =0; i<16; i++)
{
lcddata(high_alarm[chl_count][i]);
MSDelay(1);
}
// add GSM codes here
for(i=0; i<8; i++)
{
TXREG = send_sms_command[i];
MSDelay(10);
}
for(i=0; i<13; i++)
{
TXREG = destination[i];
MSDelay(10);
}
for(i=0; i<16; i++)
{
TXREG = high_alarm[chl_count][i];
MSDelay(10);
}}
if(transformer_data[chl_count] < lower_limit[chl_count])
{
lcdcmd(0x01); //Clear display
MSDelay(1);
lcdcmd(0x80); // line 1, position 0
MSDelay(1);
for(i =0; i<16; i++)
{
lcddata(low_alarm[chl_count][i]);
MSDelay(1);
}
// add GSM codes here
for(i=0; i<8; i++)
{
TXREG = send_sms_command[i];
MSDelay(10);
}
for(i=0; i<13; i++)
{
TXREG = destination[i];
MSDelay(10);
}
for(i=0; i<16; i++)
{
TXREG = low_alarm[chl_count][i];
MSDelay(10);
}}
BUZZER = ON;
INPUT_RELAY = OFF;
OUTPUT_RELAY = OFF;
while(1); //halt
}
} // end of if(1)
}// end of for loop
} // end of while
} // end of main()
void delay(unsigned int millisec)
{
unsigned int loopcount;
for(loopcount = 0; loopcount < millisec * 20; loopcount++)
{;}
}
void inputting()
{ unsigned char collected_data,count,temp;
// GIE = 0;
ADCON1 = 0x41;// left justified,frq = fosc/4,AN3 analog +ref,all other ADx analog ip
// ADIF: A/D Converter Interrupt Flag bit
// 1 = An A/D conversion completed
// 0 = The A/D conversion is not complete
ADON = 1; // power on to adc module
MSDelay(1);
if(chl_count == 0)
{ADON = 1; // power on to adc module
CHS2 = 0; // to select AN0 adc input
CHS1 = 0; // do
CHS0 = 0; // do
ADCON0 = 0x85; // 0000 0101 start of conversion of ADC
while(ADIF == 0);
while(ADCON0 == 0x85);// wait till end of conversion
collected_data = ADRESH;
MSDelay(10);
// GIE = 1;
// collected_data = 101;// debug
}
if(chl_count == 1)
{ADON = 1; // power on to adc module
CHS2 = 0; // to select AN1 adc input
CHS1 = 0; // do
CHS0 = 1; // do
ADCON0 = 0x8D; // 0000 1101 start of conversion of ADC
while(ADIF == 0);
while(ADCON0 == 0x8D);// wait till end of conversion
collected_data = ADRESH;
MSDelay(10);
// GIE = 1;
// collected_data = 102;// debug
}
if(chl_count == 2) // sub routine of oil level
{SENSOR_RELAY = 0;
MSDelay(100);
CREN = 1; // rec enabled
temp = RCREG;
do
{ while(RCIF == 0);
temp = RCREG;
}
while(temp != 0x0D); // 0x0D = CR (carrage return)
for(count = 0;count < 8; count++)
{ RCIF = 0;
while(RCIF == 0);
distance_buffer[count] = RCREG;
}
MSDelay(100);
SENSOR_RELAY = 1;
collected_data = (distance_buffer[0]-‘0’)*100 +
(distance_buffer[1]-‘0’)*10 +
(distance_buffer[2]-‘0’);
}
if(chl_count == 3) // AN3 is not available as it used for +ref ip
{ADON = 1; // power on to adc module
CHS2 = 1; // to select AN7 adc input
CHS1 = 1; // do
CHS0 = 1; // do
ADCON0 = 0xBD; // 0011 1101 start of conversion of ADC
while(ADIF == 0);
while(ADCON0 == 0xBD);// wait till end of conversion
collected_data = ADRESH;
MSDelay(10);
// GIE = 1;
// collected_data = 104;// debug
}
if(chl_count == 4)
{ADON = 1; // power on to adc module
CHS2 = 1; // to select AN5 adc input
CHS1 = 0; // do
CHS0 = 1; // do
ADCON0 = 0xAD; // 0010 1101 start of conversion of ADC
while(ADIF == 0);
while(ADCON0 == 0xAD);// wait till end of conversion
collected_data = ADRESH;
//GIE = 1;
// collected_data = 105;// debug
}
if(chl_count == 5)
{
ADCON = 1; // power on to adc module
CHS2 = 1; // to select AN6 adc input
CHS1 = 1; // do
CHS0 = 0; // do
ADCON0 = 0x35; // 0011 0101 start of conversion of ADC
while(ADIF == 0);
while(ADCON0 == 0x35);// wait till end of conversion
collected_data = ADRESH;
MSDelay(10);
// GIE = 1;
//collected_data = 106;// debug
}
transformer_data[chl_count] = collected_data;
} // end of inputting
void lcdcmd (unsigned char value)
{
// ldata = value; // put value on the pins
LCD = value;
rs = 0;
rw = 0;
en = 1; // strobe the enable pin
MSDelay(1);
en = 0;
return;
}
void lcddata (unsigned char value)
{
// ldata = value; // put the value on the pins
LCD = value;
rs = 1;
rw = 0;
en = 1; // strobe the enable pin
MSDelay(1);
en = 0;
return;
}
void MSDelay (unsigned int i)
{
unsigned int j,k;
for(k=0;k<i;k++)
{
for(j=0; j<100; j++)
{;}
}
}

CHAPTER 5
Tests and Results

For performing the Experimental test of condition monitoring and controlling of transformer ,we need a transformer, some sensor ,logic level converter and GSM modem .All of them have been explained previously now the test which are performed on the Transformer are explained below. The main instrument that is transformer with its rating is explained below in the table 5.1

Rating 125VA
Phase Single
Frequency 50 Hz
HV 230V
LV 230V

Table 5.1 basic design detail of the transformer under test
Experimental Test which are to be performed on the Transformer are listed below in the
Table 5.2
1. Input voltage test
2. Output voltage test
3. Input current test
4. Output current test
5. Temperature rise test
6. Oil level test

Table 5.2 Test to be performed on the transformer

Before performing the Experimental test of condition monitoring of Transformer some Reference value (maximum and minimum limit) have to be define which is shown in the Table 5.3
Sr .no Parameter Max. limit Min. limit
1 Input voltage(V) 250 150
2 Output voltage (V) 250 150
3 Input current (mA) 250 –
4 Output current(mA) 250 –
5 Temperature (??C) 70 –
6 Oil level (cm) 30 20

Table 5.3 Reference value for the transformer under test

Winding temperature test of the transformer under test (125VA)
For a prototype it is not feasible to increase the winding temperature .Experimentally fault created by placing temperature sensor near the glowing bulb and then measuring its temperature. If it exceed 70 ??C (as maximum set reference value is 70 ??C ) then the relay trips and at the same time message is sent to the mobile user as shown in the fig

Fig. Temperature test on transformer and their result

Some more result under varying temperature has been recorded and shown in the table 5.4
Sr. no. Load (W) Input voltage(V) Winding Temperature(??C) Result
1 60 218 65 Normal
2 60 218 70 Normal
3 60 217 71 Temperature is high
4 60 219 75 Temperature is high
5 60 216 72 Temperature is high

Oil level test of the transformer under Test(125VA)
Experimentally fault created by measuring the distance from a reference point. Reference value is fixed between 20cm and 30 cm.If it exceeds above 30cm then the LCD displays ‘oil level is minimum’ or if it’s below 20 cm then the LCD displays ‘oil level is maximum’ it will check the condition 10 times if the condition is true, then only the relay operates and message is sent to the mobile user as shown in the figure

Fig. Oil level test using oil sensor (HC-SR04) and their result

Some more oil level test performed and their result are shown in the table

Sr. no Load
(W) Input voltage(V) Oil level
(cm) Result

1
25
216
21 Normal

2
25
215
22 Normal

3
25
214
32 Oil level is minimum

4
25
216
16 Oil level is maximum

Table .oil level test using the of transformer under test
Input voltage and output voltage test on the transformer under test
We are attempting to give that type situation using potentiometer. Using potentiometer we will vary the voltage at the input side as well as at the output side. If the value exceeds the set reference value for input and output voltage.
The reference value of the input and output voltage is 250V.
By varying potentiometer we change the value to 255V.
It is more than the reference value so the system will display on the LCD and send message to the mobile user ‘output voltage high’.
The following displays are obtained during the operation.

Fig voltage test of transformer (125VA) using potential Transformer
Similarly the input voltage test can be carried out by varying the potentiometer value on the input side of the transformer.
Overload test on the transformer under test

Fig overload test of the transformer(125VA)

Sr. no. Load
(W) Input voltage(V) Input
Current
(mA) Result Remarks
1 14 219 84 Normal The input voltage is kept constant and as the load(watts) increases
the input current also
Increases.As input current increases so the output current increases as it is a isolated
transformer(125VA)
2 15 218 84 Normal
3 25 217 115 Normal
4 60 225 205 Normal
5 74 215 234 Normal
6 85 218 255 Input current high
7 100 220 260 Input current high

Other of Communiction (Receiving msg)
Other way of communication (i.e receiving msg from the microcontroller).When the operator is not present at the transformer site and if he wants to know the condition of transformer.He can easily know the various parameter condition by simply sending the unique password stored in the programming of the microcontroller to the SIM card number placed in the GSM modem .He will soon receive the msg (depending on the network) containing the information or values of the transformer parameter.The following display are obtained during operation.

Fig. result of the message send and received

Trouble shooting and their remedies

Sr. No. Trouble Remedies
1. The time taken for input and output current measurement was long because of the large value of resistance used.
So placing a resistor of 10k in parallel with large resistance, so the all over resistance will be minimized so thus the time. (t=0.69RC)
2. The input analog pin was taking garbage value.
So placed a RC filter at the input of the analog pin of the analog PORTA

3. As the current of 500mA is to be sensed and for measuring this small amount of current CT is not available in the market.
So we are using VT as CT by placing resistor in parallel with the secondary coil of the VT. So it will measure value of current as (V= IR)
4. There is only one pin in the microcontroller for the serial reception from the GSM modem and two parameter require this pin So a two way operating relay is used so one side it measure the oil level and the other side it send message from the mobile user to microcontroller

CHAPTER 5
CONCLUSION

We have design a circuit for online monitoring and controlling parameter of transformer such as overvoltage, overload, increase in winding temperature, rise and fall of oil level in transformer.

The GSM based condition monitoring of transformer is quite useful as well as reliable as compared to the manual monitoring as it is not always possible to monitor the oil level, winding temperature, load current and overvoltage manually . After receiving message of any abnormality, the operator can take action immediately to prevent any catastrophic failure of the transformer .Thus; this is the convinent way of avoiding the catastrophic failure and thus saves the economical cost of replacing the transformer.

Use of GSM technique provides speed of communication with distance independentancy. This way of sending and receiving message based communication is easy and fast and is even reliable .It is also cost effective compared to other methods of online monitoring of transformer.

FUTURE SCOPE
A DTMF (Dual Tone Multi Frequency) technology can be included to this system for switching off the load automatically with help of the frequency generated from the keypad of the Mobile. A server module can be included to this system for receiving and storing transformer parameters information periodically about all the distribution transformers of a particular utility in a database application. This database will be a useful source of information on the utility transformers. Analysis of these stored data helps the utility in monitoring the operational behavior of their distribution transformers and identifies faults before any catastrophic failures thus resulting in significant cost saving as well as improving system reliability.

6. REFERENCES
PAPERS
[1] Amit Sachan Department of Energy & Power Engineering NIMS University, Jaipur, Rajasthan ,’GSM BASED SCADA MONITORING AND CONTROL SYSTEM
SUBSTATION EQUIPMENT’, International Journal of Engineering Research Technology (IJERT) Vol. 1 Issue 5, July ‘ 2012

[2] Vadirajacharya.K,Ashish Kharche, Harish Kulakarni, Vivek Landage,’ Transformer Health Condition Monitoring Through GSM Technology’, International Journal of Scientific & Engineering Research Volume 3, Issue 12, December-2012.

[3] Dr.J.Jayakumar, J.Hephzibah ,JoseQueen, ThanuJames, G.Hemalatha, NeethuLonap pan ,’Distribution Transformer Monitoring Using GPRS’, International Journal of Scientific & Engineering Research, Volume 4, Issue 6, June- 2013.

[4] Anurudh Kumar, Ashish Raj, Abhishek Kumar, Sikandar Prasad & Balwant ,’Method For Monitoring of Distribution Transformer ‘,Undergraduate Academic Research Journal (UARJ), ISSN: 2278 ‘ 1129, Volume-1, Issue-3,4, 2012

[5] Mallikarjun Sarsamba, Prashant Sangulagi , Dr. Raju Yanamshetty ,’The Load Monitoring and Protection on Electricity Power lines using GSM Network International Journal of Advanced Research in Computer Science and Software Engineering , ISSN: 2277 128X Volume 3, Issue 9, September 2013

[6] Hari Arief Dharmawan and Sam A. M. Ali,’A Compact Remote Monitoring System for a Three-Phase 10-kVA Energy-Efficient Switchable Distribution Transformer’. IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 61, NO. 3 MARCH 2012.

[7] Perfecto Marino, Francisco Poza, Santiago Otero, Fernando Machado,’Development of Condition Monitoring Instrumentation for Sensing Power Transformers’. 1st International Conference on Sensing Technology, Palmerston North, New Zealand November 21-23, 2005

[8] Balint Nemeth, Szilvia Laboncz, Istvan Kiss,’Condition Monitoring of Power Transformers using DGA and Fuzzy Logic’. 2009 IEEE Electrical Insulation Conference, Montreal, QC, Canada, 31 May – 3 June 2009

[9] Manes F. Cabanas, Member, IEEE, Manuel G. Melero, Francisco Pedrayes, Carlos H. Rojas, Gonzalo A. Orcajo, Jos?? M. Cano ,’A New Online Method Based on Leakage Flux Analysis for the Early Detection and Location of Insulating Failures in Power Transformers Application to Remote Condition Monitoring’. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 22, NO. 3, JULY 2007

BOOKS
[1] PIC Microcontroller and Embedded Systems: Using Assembly and C for PIC18
by Muhammad Ali Mazidi, Rolin McKinlay, Danny Causey .

[2] The 8051 Microcontroller &Embedded System, using assembly and C By Kennethayala ,Dhananjay V. Gadre.

[3 ] A text book of Electrical Technology in SI units Volume 2 AC& DC Machines by B.L Theraja and A.K Theraja

[4] Theory and Performance of Electrical Machines is a book on Electrical Engineering And Technology by J. B. Gupta.

[5] Programming in ANSI C 4E, E Balagurusamy Tata McGraw-Hill Education, 2008 ‘C (Computer program language)

WEBSITE

[1] http://ww1.microchip.com/downloads/en/devicedoc/39582b.pdf

[2] http://www.chipswinner.com/ends/MAX232.pdf

Appendix
List of Symbols and abbrevation
A) Symbol used for unit
A unit system with rationalized M.K.S basis is used throughout the thesis principle units are listed below with their abbreviations.

Quantity Unit Symbol used
Current Ampere A
Frequency Cycle per second Hz
Length Metre M
Resistance Ohm ‘
Capacitance Farad F
Voltage Volts V
Power Watt W

B) Symbol used for notation:
V- voltage
A- current
K- kilo
M- mega
??- micro
m- mili
F- farad
c ‘ centimeter
mA- milliampere

C) Abbrevation
GSM – Global System for Mobile Communication
SMS ‘ Short Message Service
PIC- Peripheral Interface Controller
IC- Integrated Circuit
SIM- Subscriber Identity Module
HV ‘ high voltage side
LV- low voltage side
AT command- Attention command
LCD ‘ Liquid Crystal Display
PT or VT ‘ Potential Transformer or Voltage Transformer
CT- Current Transformer
Tx- Transmission
Rx- Reception
EN ‘Enable
RW ‘ Read /Write

Electrical characteristics of PIC16F877A
Absolute Maximum Ratings
Parameters Range
Ambient temperature under bias -55 to +125??C
Storage temperature -65??C to +150??C
Voltage on any pin with respect to VSS (except VDD, MCLR. and RA4) -0.3V to (VDD + 0.3V)
Voltage on VDD with respect to VSS -0.3 to +7.5V
Voltage on MCLR with respect to VSS (Note 2) 0 to +14V
Voltage on RA4 with respect to Vss 0 to +8.5V
Total power dissipation (Note 1) 1.0W
Maximum current out of VSS pin 300 mA
Maximum current into VDD pin 250 mA
Input clamp current, IIK (VI < 0 or VI > VDD) ??20 mA
Output clamp current, IOK (VO < 0 or VO > VDD) ??20 mA
Maximum output current sunk by any I/O pin. 25 mA
Maximum output current sourced by any I/O pin 25 mA
Maximum current sunk by PORTA, PORTB and PORTE (combined) 200 mA
Maximum current sourced by PORTA, PORTB and PORTE (combined) 200 mA
Maximum current sunk by PORTC and PORTD (combined) 200 mA
Maximum current sourced by PORTC and PORTD (combined) 200 mA

Note 1: Power dissipation is calculated as follows: Pdis = VDD x {IDD – ?? IOH} + ?? {(VDD – VOH) x IOH} + ??(VOl x IOL)
Note 2: Voltage spikes below VSS at the MCLR pin, inducing currents greater than 80 mA, may cause latch-up.Thus, a series resistor of 50-100?? should be used when applying a ‘low’ level to the MCLR pin rather than pulling this pin directly to VSS

Electrical characteristics of LM35

Parameter Conditions LM35
Units
(Max.)

Typical Design limit tested limit
Accuracy T A=+25??C
T A=’10??C
TA=TMAX
T A=TMIN ??0.4
??0.5
??0.8
??0.8 ??1.0

??1.5

??1.5 ??C
??C
??C
??C
Nonlinearity TMIN’TA’TMAX
??0.3 ??0.2 ??C
Sensor Gain TMIN’TA’TMAX
+10.0 +9.8 mV/??C
Load Regulation T A=+25??C
TMIN’TA’TMAX
??0.4
??0.5 ??2.0 ??5.0 mV/mA
mV/mA
Line Regulation T A=+25??C
4V’Vs’ 30V ??0.01 ??0.1 ??0.2 mV/V
mV/V
Quiescent Current V S=+5V, +25??C 56 80 56 ??A
Change of Quiescent Current 4V??VS??30V, +25??C 0.2 2.0 ??A
Temperature Coefficient of
Quiescent Current +0.39 +0.7 ??A/??C
Minimum Temperature for Rated Accuracy IL=0 +1.5 +2.0 ??C
Long Term Stability T J=TMAX, for
1000 hours ??0.08 ??C

Note 1: Accuracy is defined as the error between the output voltage and 10mv/??C times the device’s case temperature, at specified conditions of voltage, current, and temperature (expressed in ??C).
Note 2: Nonlinearity is defined as the deviation of the output-voltage-versus-temperature curve from the best-fit straight line, over the device’s rated temperature range.
Note 3: Quiescent current is defined in the circuit.
Note 4: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions.
Note 5: Human body model, 100 pF discharged through a 1.5 kW resistor.
LCD command and their function