COVER PAGE DECLARATION This report is my own original work based on the research I made to the best of my abilities and it hasn’t been presented anywhere else for academic purpose

COVER PAGE
DECLARATION
This report is my own original work based on the research I made to the best of my abilities and it hasn’t been presented anywhere else for academic purpose.
LANGAT KIPNGENO NEHEMIAH TLE/36/13
Signed…………………… Date: ………………….…
Project supervisor:
MR SEVERINUS KIFALU
Signed: …………………….. Date: ………………………

ACKNOWLEDGEMENTI wish to sincerely acknowledge and appreciate the significant contribution made by all those in one way or the other assisted us during the process of preparing this report.

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Many thanks go to the Department of Electrical Engineering at Moi University for the learning opportunity that have been granted to me for the five years I have been a student at this institution
Special thanks go to Mr. Severinus Kifalu, my project supervisor, for his insights, objective suggestions and guidance throughout the undertaking of this project.

Table of Contents
TOC o “1-3” h z u DECLARATION PAGEREF _Toc523892999 h iiACKNOWLEDGEMENT PAGEREF _Toc523893000 h iiiABSTRACT PAGEREF _Toc523893001 h viiCHAPTER ONE PAGEREF _Toc523893002 h 1INTRODUCTION PAGEREF _Toc523893003 h 11.1 Overview PAGEREF _Toc523893004 h 11.2 Statement of Problem PAGEREF _Toc523893005 h 11.3 Objective of the Project PAGEREF _Toc523893006 h 21.4 Project Background PAGEREF _Toc523893007 h 31.5 Project Limitations PAGEREF _Toc523893008 h 4CHAPTER TWO PAGEREF _Toc523893009 h 5LITERATURE REVIEW PAGEREF _Toc523893010 h 52.1 Overview of Electricity sector in Kenya PAGEREF _Toc523893011 h 52.2 The Electricity Distribution system PAGEREF _Toc523893012 h 52.3 Transformers PAGEREF _Toc523893013 h 72.3.1 Introduction PAGEREF _Toc523893014 h 72.3.2 Principle of Operation PAGEREF _Toc523893015 h 82.3.3 Transformer Action PAGEREF _Toc523893016 h 82.4 Failure Analysis in Distribution Transformers PAGEREF _Toc523893017 h 92.4.1 Major Failures in Distribution Transformers PAGEREF _Toc523893018 h 102.4.2 Summary of the Causes of Transformer Failure PAGEREF _Toc523893019 h 12CHAPTER THREE PAGEREF _Toc523893020 h 16METHODOLOGY PAGEREF _Toc523893021 h 163.1 Hardware Implementation PAGEREF _Toc523893022 h 163.1.1 Design of Microcontroller based Transformer Health Monitoring Kit PAGEREF _Toc523893023 h 163.1.2 The Working Principle behind the monitoring system: PAGEREF _Toc523893024 h 163.1.3 Description of the components used in the transfer monitoring model kit PAGEREF _Toc523893025 h 183.1.3.1 Sensors: PAGEREF _Toc523893026 h 183.1.3.2 Microcontroller PAGEREF _Toc523893027 h 213.1.3.3 The GSM modem PAGEREF _Toc523893028 h 253.1.4 Power Supply to the circuit PAGEREF _Toc523893029 h 263.1.5 Prototype model development PAGEREF _Toc523893030 h 27CHAPTER FOUR PAGEREF _Toc523893031 h 30SOFTWARE IMPLEMENTATION PAGEREF _Toc523893032 h 304.1 Programming Microcontroller PAGEREF _Toc523893033 h 304.2 The Project Source code PAGEREF _Toc523893034 h 304.3 Prototype Testing and results PAGEREF _Toc523893035 h 35CHAPTER FIVE PAGEREF _Toc523893036 h 36CONCLUSION PAGEREF _Toc523893037 h 36REFERENCES PAGEREF _Toc523893038 h 37APPENDIX PAGEREF _Toc523893039 h 38
List of Figures
TOC h z c “Figure” Figure 1. Electricity distribution scheme PAGEREF _Toc523892884 h 6Figure 2 Transformer Action PAGEREF _Toc523892885 h 9Figure 3 Windings Failure in a transformer PAGEREF _Toc523892886 h 10Figure 4 Collection of images showing various types of transformer failures PAGEREF _Toc523892887 h 12Figure 5. Block Diagram PAGEREF _Toc523892888 h 17Figure 6. Interfacing temperature sensor with the Adruino circuit PAGEREF _Toc523892889 h 19Figure 7. Interfacing Current sensor with the microcontroller PAGEREF _Toc523892890 h 20Figure 8. ATMega328P microcontroller Pin diagram PAGEREF _Toc523892891 h 23Figure 9. ATMegage328 architecture PAGEREF _Toc523892892 h 24Figure 10. Detailed image of SIM800L GSM modem indicating Pinout Arrangement PAGEREF _Toc523892893 h 26Figure 11. Block diagram of regulated power supply system PAGEREF _Toc523892894 h 27Figure 12. Prototype Model PAGEREF _Toc523892895 h 28Figure 13. Circuit Diagram PAGEREF _Toc523892896 h 29
List of Tables:
TOC c “Table” Table 1. Summary of sensors used PAGEREF _Toc523892869 h 21
Table 2. ATMega328P Microcontroller Specifications PAGEREF _Toc523892870 h 21
Table 3. SIM800L features PAGEREF _Toc523892871 h 25
Table 4. Model components. PAGEREF _Toc523892872 h 38

ABSTRACTThe utility company, Kenya Power, loses an average of three hundred distribution transformers in a month. This has a negative economic impact on both the supplier and the customers. It has been observed that the three transformer workshops of Kenya Power have an average output of one hundred and fifty transformers per month. Hence it takes several days to return the affected customers back to supply
The main aim of this project is to monitor, control and protect distribution transformers from malfunctioning due to faults caused by overheating, overloading, fall in oil level, and voltage surges. This will help Kenya Power by ensuring that their distribution transformer faults are immediately realized and reported to the concern department, hence being able to maintain and repair a transformer before total breakdown and thus reducing the total number of transformer failures. This will ensure that the number and duration of power interruptions to the customer is decreased, maintenance cost reduced and also save time.

This system will be implemented using microcontroller and global system for mobile (GSM) communication technology which are very efficient and cost effective. The design will involve development of an embedded system that will monitor process and transmit information regarding four key parameters of a distribution transformer. These parameters are load current, voltage, the level of oil and the operating temperature of the transformer. The microcontroller will interact with sensors to continuously monitor the voltage, load current, temperature and oil level of the transformer. As the values of current, voltage, temperature and oil level of the transformer increase from the preset values, the microcontroller through GSM will inform the repair and maintenance personnel for appropriate action to be taken.

CHAPTER ONE
INTRODUCTION1.1 OverviewThe utility company, Kenya Power and Lighting Company (KPLC) has been mandated with the distribution of electricity throughout Kenya. The entity owns and operates both the transmission and distribution networks across the country throughout Kenya. It is responsible for purchase of all bulk electricity and is the sole supplier to end use customers throughout the country.

1.2 Statement of ProblemAmong the core components required in the transmission and distribution of electricity is the distribution transformer. In power supply systems, distribution transformers are required to step down the voltage to the required levels by end consumer. When operated under the rated conditions, transformers guarantee a long life to the utility firm. When subjected to overloading and other operations that go beyond their rated conditions, faults within internal components of the transformer develop, leading to eventual failure of the entire unit if corrections are not made within the required time. Unexpected failure of distribution transformers leads to loss of electrical supply to all the customers served by it, leading to inconveniences and losses to both the utility firm and the customers. Most of these faults develop due to overloading, voltage surges as well as drop in oil levels. In general, ineffective cooling and overloading of transformers account for over 50% of all transformer failures.
Due to the above failures, KPLC loses an average of three hundred distribution transformers in a month. This has a negative economic impact on both the supplier and the customers. It has been observed that the three transformer workshops of Kenya Power have an average output of one hundred and fifty transformers per month. Hence it takes several days to return the affected customers back to supply. Apart from the inconveniences caused, the economic losses resulting from such failures are tremendous and sometimes unrecoverable.
Although a number of monitoring devices and systems are presently been employed to observe and keep track of distribution transformers, a number of flaws and deficiencies have been identified following their use. A few of them are mentioned as follows:
Normal transformer monitoring systems only target a single transformer parameter. This could be current, voltage or oil level, each been detected using its own monitoring system.
Due to in efficiencies within the sensing devices, the monitoring system may be rendered inaccurate and unreliable. Poor performance may be due to instability, poor anti-jamming capability, and low accuracy levels of the instruments used.
Manual monitoring requires a lot of time. Due to lack of real-time monitoring, some defects are not realized on time.
Most monitoring systems do not offer any mechanisms for control in case of changes in parameter settings but rather just relay the information elsewhere.

Use of power line carrier communication (PLCC) is among preferred means by some monitoring systems to send data. However, with increased distance between the source and the receiving end, signals in power line carrier communication become subjected to serious frequency interference. Also, huge electrical noise is likely to interfere with these signals leading to inaccuracies in the transmitted data. Consequently, reliability is not guaranteed when this means of data transmission is employed in a transformer monitoring system.
1.3 Objective of the ProjectThe objective of this project is to come up with a remote monitoring and control system for distribution transformers. The system will offer real-time monitoring and control of distribution transformers to protect them from malfunctioning due to faults caused by overheating, overloading, voltage surges and fall in oil level. Apart from monitoring all the operating parameters in the transformer, the system will incorporate control commands to rectify some of faults observed or disconnect the transformer from the supply source in case of acute faults that may lead to severe damages on the transformer. Through use of mobile networks, all this will be monitored in real-time by relaying the information to the right personnel in the KPLC monitoring and control center.
Through real-time remote monitoring of transformers, useful information regarding the health of transformers is obtained. This helps utility firms to optimally use the transformers and also keep them in operation for longer. Various faults are also detected early enough and rectified to prevent serious damages or even total failure of the unit. This not only leads to cost savings but also increases reliability while avoiding unnecessary inconveniences to the power consumers. In the long run, it will reduce the number and duration of power interruptions to the customer, lower maintenance costs and also save on time.

1.4 Project BackgroundMost of the abnormalities in transformer are as a result of variation in different parameters such as the load current, voltages, operational temperature, level of oil, and contamination of oil among others. We have come up with a model of a microcontroller based on Global System for Mobile (GSM) communication technology in order to achieve the monitoring and control of these parameters.

First sensors are installed which reads and measures the various physical quantities from the distribution transformer and converts them into electrical signals. In this project, the sensors used are for measuring temperature, voltage, current and oil level. The signals from these sensors have then been linked to the microcontroller for processing. The microcontroller interacts with the sensors to continuously monitor the voltage, load current, temperature and oil level of the transformer. A GSM based modem is interfaced with the microcontroller through an adapter by which it uploads the information to a utility control center, from where real-time monitoring is done.

As the values of current, voltage, temperature and oil level of the transformer increase from the preset values, the microcontroller through GSM will inform the repair and maintenance personnel for appropriate action to be taken. The voltage, current and temperature values will be displayed on an LCD display and the kind of the fault will be indicated using LED indicators .An increase in temperature above the benchmark will turn a fan to cool the transformer. The microcontroller will also send appropriate control signal to appropriate circuit breakers that will disconnect the transformer in case of acute faults such as a short-circuits or excessive fall in oil level and initiate an alarm.

1.5 Project LimitationsAlthough the project takes a diverse approach on the major causes of distribution transformer failures when designing the monitoring system, the scope of the project faces the following limitations:
Only four parameters are monitored using the system. These four are temperature, voltage, current and oil levels in the transformer. Pressure measurements among other parameters that may be necessary to monitor at times have not been considered since they do not contribute greatly to transformer failure, although they cannot be ruled out entirely.

Due to the varying architectural designs found on different transformers, the monitoring system may require unique modifications for the sensors to be installed on some transformers.
Distribution transformers have different rated capacities. Some of the sensors advocated for in this project may not be suitable on transformers that have a high load capacity.

CHAPTER TWO
LITERATURE REVIEW2.1 Overview of Electricity sector in KenyaMajority of electricity in Kenya is generated by the Kenya Electricity Generating Company (KenGen). The bulk of electricity is then purchased by Kenya Power and Lighting Company (KPLC), who is the sole supplier of electricity to end use customers throughout the country. The company owns and operates both the transmission and distribution networks throughout Kenya. The responsibility of constructing new transmission lines across the country is nonetheless done by Kenya Electricity Transmission Company (KETRACO). These lines are then handed over to KPLC to operate and maintain.
2.2 The Electricity Distribution systemIn general, the power supply line network from the generating station to the end consumer can be divided as follows:
Transmission System
Distribution System
Each of these two can be explored in more details by categorizing them as primary transmission and secondary transmission. The same can be done for distribution system by exploring it under primary distribution and secondary distribution. This is shown in the power distribution system scheme (Figure 1).
Primary Transmission: From the generating station, the voltage is stepped up using power transformers (to 132kV, 220 kV, 500kV or greater) and transmitted to receiving center through three phase 3-wire overhead transmission system.

Secondary Transmission: At receiving station, mostly areas far from city (outskirts), the voltage is lowered to approximately 66 or 33kV. The power is then transmitted by three phase three wire overhead transmission system to various sub stations.
Primary Distribution: At a substation, the voltage is stepped down further to approximately 11kV through use of step-down transformers. Heavy power consumers, such as industries and manufacturing plants whose demand may be as high as 11kV, are supplied from this line in three phase three wire overhead system.
Secondary Distribution: Distribution substations receive electrical power from the primary distribution substation. Here, the voltage is reduced to 440V by step down transformers. These transformers are mainly referred to as distribution transformers and are located close to the consumer area. This distribution system constitute of three phase four wire system. In three phase supply system, there are 400v between any two phases while in single phase supply system, there are 230 V between a neutral and phase (live) wire.

Figure 1. Electricity distribution schemeNote
Since there are only a few heavy energy consumers located in urban areas in Kenya, secondary distribution in Kenya is widespread, ranging from urban and suburban to the rural areas. As a result, KPLC relies heavily upon the country-wide network of distribution transformers in order to facilitate electrical energy distribution to the final consumer.
2.3 Transformers2.3.1 IntroductionTransformers are electrical devices that transfer electrical energy between circuits through the principle of electromagnetic induction (referred to as transformer action as well). . They are used to either step down (reduce) or step up (increase) the voltage. Although there is an effective change in current and voltage, no interferences to the frequency of the electrical power are made during the transformer action. Since transformers are based on the principle of electromagnetic induction, they only work with input sources that vary in amplitude.
Depending on their voltage ratings, transformers can be classified into two. Transformers with ratings above 500kVA are referred to as Power transformers and are used in most cases to step up the voltage for primary transmission. Transformers with ratings below 500 kVA are generally called distribution transformers. They are mostly used to step down voltage for distribution of electrical power to the end users. Examples of these are pole-top and small, pad-mounted transformers that mostly serve residential areas, institutions and small businesses as well.
Step-up transformers receive electrical energy at generator voltage and deliver it at higher voltage for transmission lines. Conversely, step-down transformers receive electrical energy at a higher voltage and lower its voltage for distribution to various loads. Electrical devices that use coils, such as transformers in this case, are constant wattage devices. This is interpreted to mean that voltage multiplied by current must remain constant; therefore, when voltage is increased, the current is reduced and vice versa.
In electrical power transmission, high voltage and low current reduce the required size and cost of transmission lines. Due to low current, transmission power losses are also tremendously reduced. In this sense, transformers make it possible to deliver electric power over long distance economically.
2.3.2 Principle of OperationThe basic principle of operation for transformers is coined from the fact that electrical energy can be transferred efficiently from one circuit to the other through magnetic induction. Basically, a transformer is made up of two coils of wire, one referred to as primary windings while the other one is called secondary winding. When an alternating current source is introduced on one circuit containing either primary or secondary windings, an alternating magnetic field is generated within the transformer core. Alternating magnetic lines of force, called “magnetic flux,” circulate through the core. When these alternating magnetic flux lines cut through the second windings, a voltage is induced. When a circuit is connected to the second windings, current begins to flow in the connected circuit.
2.3.3 Transformer ActionTransformer action majorly depends upon magnetic lines of force (flux) mentioned above. When the primary windings of a transformer are energized through an AC power supply, electrons begin to flow. As current begins the positive portion of the sine wave, lines of magnetic force (flux) develop outward from the coil and continue to expand until the current is at its positive peak. The magnetic field is also at its positive peak. The current sine wave then begins to decrease, crosses zero, and goes negative until it reaches its negative peak. The magnetic flux switches direction and also reaches its peak in the opposite direction. With a 60 Hz AC power circuit, the current changes (alternates) continually 60 times per second.

The amount of current and the number of turns in the windings determine the strength of the magnetic field created. When the current is increased, the magnetic field generated becomes stronger. Likewise, when there are more turns in the windings, the magnetic field increases. When there is no current in the primary windings, no magnetic field is generated.
When a coil is placed in an AC circuit, as shown in figure 2, current in the primary coil will be accompanied by a constantly rising and collapsing magnetic field. When another coil is placed within the alternating magnetic field of the first coil, the rising and collapsing flux will induce voltage in the second coil. When an external circuit is connected to the second coil, the induced voltage in the coil will cause a current in the second coil. The coils are said to be magnetically coupled. However, they are electrically isolated from each other.

Many transformers have separate coils, as shown in figure 2, and contain many turns of wire and a magnetic core, which forms a path for and concentrates the magnetic flux. The source of electrical energy is connected to the primary windings. The windings that receive energy from the primary winding, via the magnetic field, are called the secondary winding. Either the high- or low-voltage winding can be the primary or the secondary. With Power Generator Step-Up Units (GSUs), the primary winding is the low-voltage side (generator voltage), and the high voltage side is the secondary winding (transmission voltage). In most distribution transformers, Where power is used (i.e., at residences or businesses), the primary winding is the high-voltage side, and the secondary winding is the low-voltage side. For step up transformers, such as the power transformers, the secondary windings have more turns than the primary windings. On the other hand, step-down transformers, such as distribution transformers, the secondary windings have a fewer number of turns compared to the primary windings. In actual sense nonetheless, the amount of power available in the secondary windings is less compared to the amount supplied in the primary due to various energy losses that occur within the transformer.

Figure 2 Transformer Action
2.4 Failure Analysis in Distribution TransformersDistribution transformer form a very critical link in the distribution system and in their absence, supply of electricity to end consumers would not be made possible. With increasing population, the demand for distribution transformers continues to increase. Failure of distribution transformers leads to economic losses by the utility firm. On the other hand, it creates very many inconveniences to the consumers. As described in the introduction section of this report, the failure rate of distribution transformers in Kenya is above the rate at which they are replenished. Detailed in this section is an analysis of major failures in distribution transformers.
2.4.1 Major Failures in Distribution Transformers
As a result of operation of transformers under different conditions, faults and defects may develop in different transformer components due to thermal, electrical and mechanical stress leading to eventual component failures as described below:
Winding failure
Windings are an important part of a distribution transformer as they play a critical role in the action of transformer. These windings withstand dielectric, thermal and mechanical stress during this process. Due to these stresses, breakage of windings eventually takes place. Dielectric faults caused by line surges, resulting from overcurrent and voltage surges are the main causes of winding failure. Others are due to Due to the copper line resistance thermal losses occur leading to thermal losses and also mechanical faults leading to distortion, loosening or displacement of the windings.

Figure 3 Windings Failure in a transformerBushing Failure
In a transformer, bushes act as insulating devices. They insulate a high voltage electrical conductor to pass through an earth conductor. Paper insulators are used for this purpose. The insulation is further enhanced by the use of transformer oil which surrounds the paper insulators. Sudden high fault voltages, loosening of conductors and seal breaking are among the most common causes of this fault.
Core failure
Transformer core forms an integral part of the unit and plays a critical role in transformer action by concentrating the magnetic flux between the two circuits. Transformers usually have laminated steel cores that are surrounded by transformer windings. Due to poor maintenance, old oil and even corrosion, the lamination of the core may become defective. This leads to increased eddy currents within the core leading to increased thermal energy within the unit. This consequently leads to overheating that destroys the core and the windings as well. Figure 4 shows an example of core failure.
Tank Failures
The tank holds the oil contained in the transformer while acting as a support system for various components within a transformer. Defects in the tank take place as a result of environmental stress, corrosion, high humidity and sun radiation. These defects occur in form of cracks within the tank that lead to eventual oil leakage from the transformer. Leakages lead to reduced level of oil in the transformer, which may initiate overheating in the unit. Crack may also facilitate entry of moisture and other contaminants into the transformer, damaging the internal components.

Cooling system failure
Cooling system is responsible for maintain the operating temperatures within the required limits by reducing heat produced due to copper and iron losses. The cooling system contains cooling fans, oil pumps and water-cooled heat exchangers. Cooling system failure lead to heat buildup and also cause more gas pressure buildup eventually causing a transformer to blow. The leading causes of cooling system failure are low oil levels in the transformer as well as faults in cooling fans.
Tap Changer Failure
The tap changer function in the transformer is to regulate the voltage level by either adding or removing turns from the secondary windings. Tap Changer failure leads to changes in the turn ratio of the windings resulting in wrong power outputs. Voltage surges, breakdown of motor in the tap changer as well as lack of maintenance are the main causes of tap changer failure. Figure 4 shows an example of tap changer failure.

Figure 4 Collection of images showing various types of transformer failures2.4.2 Summary of the Causes of Transformer Failure
From research and studies carried out in this area, analysis has established that the basic causal factors for failure in distribution transformers remain the same. As mentioned above, most of the faults that occur are as a result of electrical, mechanical and thermal stress on transformer components. The most common factors that reduce the life expectancy of transformers have been discussed below.

Line Surges
Among transformer failures, line surges are the leading cause for most of them. This category includes switching surges, voltage surges, overcurrent, and other abnormalities related to transmission and distribution of electricity.
Voltage surges.

Voltage surges and overvoltage constitute the largest portion of line surges. Transient Surge Voltage and other high voltages can come about due to;
Arcing ground when the neutral point is isolated.

Switching operation of different electrical equipment that consume a lot of electrical power
Atmospheric Lightening Impulse.

Voltage surges causes breakdown of the insulation between turns which may create short circuit between turns. It is the leading cause of winding failure, bush failure and tap changer failure.
Overcurrent.

Just like voltage surge, overcurrent constitutes line surges. It leads to breakage of insulation amongst the windings and can cause internal short-circuiting in the transformer. This eventually leads to windings failure.
Overheating
In most cases, distribution transformers will fail over time due to overheating. The life of a transformer is normally dependent upon the life of the insulation. According to IEEE standards, transformer insulation deteriorates as a function of time and temperature. Insulation is mostly achieved through use of paper and oil. When exposed to elevated operating temperature, the paper insulation loses its mechanical and electrical strength, thereby becoming weak.
Sufficient eddy current flow due to core lamination failure can lead to overheating. Cooling system failure also leads to overheating in distribution transformers.
Contamination of transformer oil or reduction in oil level
Transformer oil plays a critical role in the insulation and cooling of the transformer. A reduction in its level will have the following adverse effects on the operation of a transformer.
Reduction in oil level leads to poor insulation in the transformer, thus affecting core and windings.

Oil is used for cooling purposes. Reduction of oil causes over-heating with damages different parts of the transformer.

Moisture and contamination in the oil leads to damage in the internal components of the transformer, including the copper windings leading to the ultimate failure of the whole unit.
Overloading
Overloading occurs in transformers that have experienced a sustained load that exceeded the nameplate capacity. Often, overloading occurs when the load is slowly increased until the rated capacity of a transformer is exceeded. Overloading 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. This happens because overloading leads to excessive temperatures that lead to weakening of the paper insulation. Current increases the hottest-spot temperature (and the oil temperature), and thereby decreases the insulation life span. Deterioration of the insulation consequently leads to immature failure of a transformer.
Over Excitation
The flux in the transformer core is directly proportional to the applied voltage and inversely proportional to the frequency. Over excitation occurs 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. Over excitation results in excess flux, which causes transformer heating and increases exciting current, noise, and vibration.

Inadequate Maintenance
Surprisingly, inadequate Maintenance is a leading cause of transformer failures. This category includes disconnected or improperly set controls, loss of coolant, accumulation of dirt and oil, and corrosion. Poor maintenance has to take blame for transformer failure that occurs due to faults that develop over time and could have been rectified early enough.
Chapter summary
From the above analysis of failure in distribution transformers, it has been established that the life of a transformer is directly linked to two parameters; insulation and operating temperature. These parameters are greatly influenced by these variables:
The supply voltage
The load current
The ambient, oil and windings temperature
The level of oil in the transformer.
In the following section, a remote monitoring system has been discussed in detail to ensure these variables are maintained within the normal working range to increase the working life of a transformer and create more utility to both the supplier and the consumer.
CHAPTER THREEMETHODOLOGYThis chapter details the hardware implementation of the project. It details how the design is constructed and the working of the design model with the help of circuit diagram. The features of sensors, microcontroller and GSM module used are well elaborated.
3.1 Hardware ImplementationThis section details the hardware implementation of the project. The designed model together with its components is explained herein.
3.1.1 Design of Microcontroller based Transformer Health Monitoring KitThe online monitoring system will comprise of the following fundamental components
Sensors
Microcontroller
GSM modem
Display unit
3.1.2 The Working Principle behind the monitoring system:Sensors are supposed to be installed at the transformer site in order to monitor the various parameters as required. The parameters are converted into an analog signal to be processed in signal conditioning circuits
The signals are then passed through to the microcontroller. The ADC is used to read the parameters and convert them into digital signals that can be read and processed by the microcontroller. The built-in EEPROM hosts the embedded software algorithm that takes care of the parameters acquisition, processing, displaying, and transmission. The built-in EEPROM also saves the online measured parameters.
The GSM modem is then interfaced with the microcontroller to allow for the communication of information related to the transformer parameters and status.
The GSM modem then relays the information containing the transformer parameter values to mobile users at the control center for real-time monitoring. In this case, the information will be viewed online through a web-hosting platform-Ubidots.
In case of a change in readings by the sensors, the changes will be processed by the microcontroller and information relayed to the control room via the GSM modem.

The block diagram below summarizes the working principle of the transformer monitoring kit.
14287547625VOLTAGE SENSOR
VOLTAGE SENSOR
299085066675POWER SUPPLY
230V
POWER SUPPLY
230V

371475102235TRANSFORMER
00TRANSFORMER
10001251651000
1047750315595DS18B20 TEMPERATURE SENSOR
DS18B20 TEMPERATURE SENSOR

1962150191770004486275127635Ubidots.com
00Ubidots.com

2752725287655ATMEGA S28P MICROCONTROLLER
00ATMEGA S28P MICROCONTROLLER
526732512636600
4848225259715SIM800L GSM MODEM
00SIM800L GSM MODEM

1057275147320ACS712 CURRENT SENSOR
ACS712 CURRENT SENSOR
197167531369000433387532321500
37909501479550019621506413500
3429000128905POWER SUPPLY
CLOCK RESET
00POWER SUPPLY
CLOCK RESET
1047750197485FLOAT SWITCH
FLOAT SWITCH

Figure 5. Block Diagram3.1.3 Description of the components used in the transfer monitoring model kit3.1.3.1 Sensors:Initially, sensors are installed at the transformer site in order to read and measure various physical quantities from the distribution transformer and then convert them into the analog signal. Sensors are used for reading the various transformer-related parameters such as load current, supply voltage, operating temperature, oil level and gas-in-oil among others. A sensor is a device which detects and responds to a signal when stimulated externally. Since there is no limit to the number of variables that can be measured for online monitoring, an appropriate sensor technology should be adjusted to meet specific requirements of a particular transformer depending on prevailing conditions and most common factors leading to their failure.

Sensors play a very vital role in the entire implementation of this project. From the literature review, it has been established that the leading causes of distribution transformers failure are due to voltage surges, overcurrent, overheating and drop in oil levels. Owing to this, sensors have been selected and suitably designed to monitor and protect against these causal factors. The following sensors have been incorporated in our model:
Temperature sensor
A DS18B20 One-Wire Temperature Sensor has been used to measure the temperature within the transformer. The sensor has the following key specifications that make it most ideal to our model:
Programmable Digital Temperature Sensor
1-Wire communication method
Operating voltage: 3V to 5V
Wide temperature range: -55°C to +125°C with an accuracy of ±0.5°C
The image below shows how the temperature sensor is interfaced with the Adruino board.

Figure 6. Interfacing temperature sensor with the Adruino circuitCurrent sensor
An ACS712 Current Sensor Module has been used. Some of its key specifications are:
Measures both AC and DC current
Available as 5A, 20A and 30A module
Provides isolation from the load
Easy to integrate with MCU, since it outputs a low noise analog voltage
5V, single supply operation
The following image details how the sensor is interfaced into the Adruino board.

Figure 7. Interfacing Current sensor with the microcontrollerOil Level Sensor
A float switch has been incorporated as the oil level sensor. In case of mechanical movements of the float, there is a voltage generation that corresponds to the mechanical movement of the float. This voltage is used for oil level monitoring.
Voltage sensor
The voltage sensor is used to measure the applied voltage to the transformer at the measuring tap of the capacitor bushing. It acts with the capacity of the bushing as a voltage divider. Apart from the measurement of operational voltage, it can be used to detect overvoltage because the sensor has been designed to accommodate a bandwidth of some MHz.
The sensors used are summarized in table 1.
Table SEQ Table * ARABIC 1. Summary of sensors usedParameter Sensors Used
Phase Current ACS712 Current sensor
Phase Voltage Voltage (transformer) sensor
Temperature DS18B20 Temperature Sensor
Oil Level Float switch
3.1.3.2 MicrocontrollerA microcontroller is a compact integrated circuit that is designed to achieve some predefined task within an embedded system. A typical microcontroller includes a processor, memory and input/output (I/O) peripherals that are all integrated on a single chip. A number of popular families of microcontrollers exist that are used in different applications depending on their capabilities and the nature of tasks to be executed. The most commonly used microcontrollers are 8051, AVR and PIC microcontrollers.
Our monitoring system incorporated the ATmega328P microcontroller. The 8-bit microcontroller that is based on AVR RISC architecture is the most popular of all AVR controllers since it is widely used in ARDUINO boards. Some of the key features of this microcontroller are summarized in the following table:
Table SEQ Table * ARABIC 2. ATMega328P Microcontroller SpecificationsParameter Value
CPU type 8-bit AVR
Program Memory Type Flash
Program Memory Size (KB) 32
ADC Module 6channels, 10-bit resolution ADC
CPU Speed (MIPS/DMIPS) 20 MIPS at 20 MHz
SRAM (Bytes) 2048
Data EEPROM/HEF (bytes) 1024
Digital Communication Peripherals 1-UART, 2-SPI, 1-I2C
Timers 2 x 8-bit, 1 x 16-bit
Number of Analog Comparators 1(12,13 PINS)
Temperature Range (C) -40 to 85
Operating Volt Range 1.8 to 5.5
Pin Count 28 or 32
Number of programmable I/O lines 23
The ATmega328P Pinout
The Atmega328P microcontroller used has 28 pins. 14 of the pins are for digital I/O, of which 6 can be used as PWM outputs. 6 of the pins are for analog input. These I/O pins account for 20 of the pins. These pins can either function as input or output to the circuit depending on the software setting. 2 of the pins are for crystal oscillator to provide a clock pulse for the microchip. Two pins, Vcc and GND are used to provide power for the microcontroller to operate. Together with the 6 pins for analog input, the chip has 3 pins set aside for the ADC to function. The three chips are AVCC, AREF, and GND. The last pin is the RESET pin. This pin allows a program to be rerun and started over. This sums up the pinout of an Atmega328 chip, which is a total of 28 pins.
Shown below is the pinout for the Atmega328.

Figure 8. ATMega328P microcontroller Pin diagramArchitecture of ATmega328P Microcontroller
The ATmega328P is a low-power, high-performance 8-bit ?C with 2K bytes of In System Programmable Flash memory. As an 8-bit microcontroller, ATmega328 can handle data sized of up to eight (8) bits. Its built-in internal memory is around 32KB. It has an ability to store data even when electrical supply is removed from its biasing terminals. With CPU speeds of upto 20MIPS at 20MHZ, it means the AVR can execute 20 million instructions per second if the frequency is 20MHZ. By executing powerful instructions in a single clock cycle, the device achieves throughputs approaching 1 MIPS per MHz, balancing both power consumption and processing speed.

The architecture of the microcontroller is summarized in the following block diagram.

Figure 9. ATMegage328 architectureATmega328P microcontroller have a wide range of applications, most important been in embedded system projects. In this project, the microcontroller is responsible for acquisition, processing, storage and transmission of the information obtained from the various measured parameters to the GSM modem.
The software configuration for the optimal operation of this microcontroller according to our project requirements has been made in the next section.
3.1.3.3 The GSM modemA GSM modem is a wireless modem that works with a GSM wireless network. It transmits data through waves. In order to operate, it requires a SIM card from a wireless carrier.
For this project, a SIM800L GSM module has been used. This is a miniature cellular module which allows for GPRS transmission and sending or receiving data remotely. The module features compact size and low current consumption. It communicates with microcontroller via UART port. Some notable features of the modem are listed below:
Table 3. SIM800L featuresParameter Value
Supply voltage 3.8 to 4.2 V
Power consumption sleep mode ; 2.0mA
idle mode ; 7.0mA
GSM transmission (avg.): 350 mA
GSM transmission (peek): 2000mA
SIM card socket MicroSIMSupported frequencies Quad Band (850 / 950 / 1800 /1900 MHz)
Operating temperature range -40°C to + 85 °C
Interface UART (max. 2.8V) and AT commands
The SIM800L GSM module PinoutThe module has 7 total pins, which are used to interface with the ARDUINO board. The Pins and their functions are described below:
VCC: External Supply Voltage input to the modem
GND: An External Ground for the modem. 2 pins.

VDD: Microcontroller Supply voltage input for the GSM modem
RST: Modem Reset pin
RXD: Serial communication (Receiver Pin)
TXD: Serial communication  (Transfer Pin)
The locations of these pins are shown in the diagram below.

Figure 10. Detailed image of SIM800L GSM modem indicating Pinout Arrangement
The software configuration for the GSM modem has been made in the next section.
3.1.4 Power Supply to the circuitA DC Voltage Power supply is required to run the circuit. The sensors as well as the microcontroller require an operating voltage of 5 V. The voltage obtained from the main line is 230V AC while the circuit components for our model require power supply of 5V DC. Step down transformer is used to lower the electric supply to 12V AC. It is then converted to 12V DC through a full-wave rectifier. Due to Pulsating DC, The output of rectifier contains some ripples. Capacitors are used to remove the ripples and a smoothed DC power is obtained. Using a positive voltage regulator, a rated output of 5V DC power supply is obtained. This is how a fixed 5V DC power supply is achieved in the circuit in order to power the various components in the ARDUINO board.

The power supply has been simplified using a block diagram as shown below:
-952501242695Figure 11. Block diagram of regulated power supply systemFigure 11. Block diagram of regulated power supply system-9525016700500
The description for the blocks:
Transformer – Required to step down the AC power supply from 230V to 12V
Rectifier – Used to converts AC to DC. Full-wave rectifier used.

Smoothing – Used to remove ripples from the DC power supply. Capacitors used
Voltage Regulator – Sets the electrical power at a fixed 5V DC supply.

Power supply to the GSM Modem
Unlike the other components in the ARDUINO board which operate on a5V DC power supply, the GSM Modem operates on a 4.2V DC power supply. For this reason, a second step-down voltage regulator is used. For this purpose, an LM2596 step-down power module voltage regulator is used. With a rated current of 2A, and a maximum of 3A and an adjustable voltage, this power supply module was ideal for our project.
3.1.5 Prototype model development
As shown in the figure below, the ATMega328P microcontroller is the main processing element to which load current, input voltage, temperature and float sensor are connected. These four sensors are used to monitoring transformer parameters (voltage, current, temperature and oil level) Initially input from mains lines to load is monitored by current sensor. This sensor gives the current level based on load used by costumer. Output of the sensor is current in ac which is rectified and made voltage by signal conditioner circuit consisting of 4 resistors, diodes and capacitors. The electrical signals from the sensors are fed into the microprocessor for processing. When power supply is switched on, microcontroller starts program execution from zero memory location. With the help of analog inputs in the microprocessor, analog signals are converted into digital impulses. The output of the ADC is 8 bit which is readable and executable by the microprocessor.
Processed information is passed through to the GSM modem. The modem is responsible for transmitting the information received to an interface where it can be read by the relevant personnel and action taken in case there is a change in parameter readings. For this project, the information will be sent to Ubidots (https://ubidots.com/education/). Ubidots offers an ideal platform in as far as implementation of embedded engineering system projects is concerned. From their website, information sent by the GSM modem can be easily obtained. An image of the model is shown below.

Figure 12. Prototype ModelCircuit Diagram
The circuit diagram for the board is shown below.

Figure 13. Circuit DiagramCHAPTER FOURSOFTWARE IMPLEMENTATIONThis chapter details software implementation of the project as well as testing done on the prototype model.
4.1 Programming MicrocontrollerThe project is based on microcontroller programming. ARDUINO tool was used to program the code for this project. For the microcontroller to execute the code, all the necessary ARDUINO libraries had to be downloaded on the chip. Since the microcontroller has the required hardware to support USB communication, the code was uploaded through the same. Following successful program burning into the microcontroller, the chip becomes ready for use. Contained in the code were the commands for the GSM module as well.
4.2 The Project Source code#include ;OneWire.h;
OneWire ds(8); //temp sensor
char atrx_buffer100;
String payload = “transformer/1.0|POST:tranformer=>temperature:”;//14,moisture:12|end”;
char status_buff20;
/////////////////
byte i;
byte present = 0;
byte type_s;
byte data12;
byte addr8;
float celsius;
///////////////////
const int voltagePin = A1;
const int currentPin = A0;
const unsigned long sampleTime = 100000UL; // sample over 100ms, it is an exact number of cycles for both 50Hz and 60Hz mains
const unsigned long numSamples = 250UL; // choose the number of samples to divide sampleTime exactly, but low enough for the ADC to keep up
const unsigned long sampleInterval = sampleTime/numSamples; // the sampling interval, must be longer than then ADC conversion time
//const int adc_zero = 522; // relative digital zero of the arudino input from ACS712 (could make this a variable and auto-adjust it)
int adc_zero;
double Power;
double Amps ;
/////////////////////////////
int float_switch_pin = 7;
void setup() {
Serial.begin(9600);
pinMode(float_switch_pin,INPUT);
adc_zero = determineVQ(currentPin); //Quiscent output voltage – the average voltage ACS712 shows with no load (0 A)
delay(10000);
ping_GSM();
connect_tcp();
delay(1000);
}
int oil_level;
int voltage;
void loop() {
oil_level = digitalRead(float_switch_pin);
Amps = readCurrent(currentPin);
temp();
voltage = analogRead(voltagePin);
upload_data();
}
void upload_data()
{
Serial.print(F(“AT+CIPSEND
“));
confirmAtCommand(“;”, 2000);
Serial.print(payload);
Serial.print(celsius);
Serial.print(“,voltage:”);
Serial.print(voltage);
Serial.print(“,current:”);
Serial.print(Amps);
Serial.print(“,oil-level:”);
Serial.print(oil_level);
Serial.write(0x1A);
confirmAtCommand(“SEND OK”, 10000);
/* Serial.print(F(“AT+CIPRXGET=2,1460
“));
confirmAtCommand(“+CIPRXGET: 2”, 4000);*/
delay(1000);
read_serial();
}
void connect_tcp() {
//Serial.print(F(“AT+CIPRXGET=0
“));
// confirmAtCommand(“OK”, 2000);
Serial.print(F(“AT+CIPMUX=0
“));
confirmAtCommand(“OK”, 2000);
Serial.print(F(“AT+CSTT=”APN”,”safaricom”,””
“));
confirmAtCommand(“OK”, 2000);
Serial.print(F(“AT+CIICR
“));
confirmAtCommand(“OK”, 3000);
Serial.print(F(“AT+CIFSR
“));
confirmAtCommand(“OK”, 5000);
confirmAtCommand(“CONNECT OK”, 10000);
}
void close_tcp() {
Serial.print(F(“AT+CIPCLOSE
“));
confirmAtCommand(“OK”, 2000);
Serial.print(F(“AT+CIPSHUT
“));
confirmAtCommand(“OK”, 2000);
}
void ping_GSM()
{
//Serial.println(F(“ATE0
“));
//delay(500);
for (int k = 0; k < 10; k++) {
Serial.println(F(“AT
“));
confirmAtCommand(“OK”, 2000);
delay(200);
}
/*Serial.println(F(“AT+CFGRI=1
“));
confirmAtCommand(“OK”, 2000);
Serial.println(F(“AT+CMGF=1
“));
confirmAtCommand(“OK”, 2000);
Serial.println(F(“AT+CNMI=2,2,0,0,0
“));
confirmAtCommand(“OK”, 2000);
*/
}
uint8_t confirmAtCommand(char *searchString, unsigned long timeOut)
{
uint8_t index = 0;
unsigned long tOut = millis();
while ((millis() – tOut) <= timeOut )
{
while (Serial.available() > 0)
{
atrx_bufferindex = Serial.read();
// mySerial.print(atrx_bufferindex);
index++;
atrx_bufferindex = ‘