Transformer Fault Detection Using Zigbee and GSM

TRANSFORMER FAULT DETECTION USING ZIGBEE 2011-12

INTRODUCTION

In search of our project we plan to do something, which is yet to be established and must be

useful to day to day life. We analyzed the current situation and realized that if there may be

system that informs the user about various faults in the transformer, we will be able to prevent

severe damages. So we decided to develop such a system that detects transformer faults.

A system which can detect the voltage of a transformer from normal to danger and to take an

initiatives to avoid damage to a transformer.

Power transformers are designed to transmit and distribute electrical power. Depending on the

size of a transformer, replacement costs can range from a few hundred dollars to millions of

dollars. Performing offline and invasive tests also add to the replacement cost. Hence, there is an

increasing need to move from traditional schedule-based maintenance programs to condition-

based maintenance. However, a focused approach is required for diagnostics.

Department of ECE,DSCE Page 1


SYSTEM OVERVIEW

TRANSMITTER BOCK DIAGRAM



RECEIVER BLOCK DIAGRAM



BLOCK DIAGRAM DESCRIPTION :

Transformer fault detection includes the following components:

Power supply

Microcontroller

Buzzer

LCD Display

Relay

Transformer

Mobile

Transmission lines

Zigbee technology

TRANSFORMER



INTRODUCTION

The protection system of transformer is inevitable due to the voltage fluctuation, frequent

insulation failure, earth fault, over current etc. Thus the following automatic protection systems

are incorporated.

1. Buchholz devices:

A Buchholz relay, also called a gas relay or a sudden pressure relay, is a safety

device mounted on some oil-filled power transformers and reactors, equipped with an

external overhead oil reservoir called a conservator. The Buchholz Relay is used as a

protective device sensitive to the effects of dielectric failure inside the equipment. It

also provides protection against all kind of slowly developed faults such as insulation

failure of winding, core heating and fall of oil level.

2. Earth fault relays:

An earth fault usually involves a partial breakdown of winding insulation to earth.

The resulting leakage current is considerably less than the short circuit current. The

earth fault may continue for a long time and creates damage before it ultimately

develops into a short circuit and removed from the system. Usually provides

protection against earth fault only.

3. Over current relays:

An over current relay, also called as overload relay have high current setting and

are arranged to operate against faults between phases. Usually provides protection

against phase -to-phase faults and overloading faults.

4. Differential system:

Differential system, also called as circulating-current system provides protection

against short-circuits between turns of a winding and between windings that

correspond to phase-to-phase or three phase type short-circuits i.e. it provides

protection against earth and phase faults.



The complete protection of transformer usually requires the combination of these

systems. Most of the transformers are usually connected to the supply system through

series fuses instead of circuit breakers. In existing method the transformer does not

have automatic protective relays for protecting the transformer.

TRANSFORMER – DEFINITION

A device used to transfer electric energy from one circuit to another, especially a pair of

multiple wound, inductively coupled wire coils that affect such a transfer with a change in

voltage, current, phase, or other electric characteristic.



Fig 2.1 Basic Transformer

THE UNIVERSAL EMF EQUATION

If the flux in the core is sinusoidal, the relationship for either winding between its

number of turns, voltage, magnetic flux density and core cross-sectional area is given by

the universal emf equation (from Faraday’s Law):

E=2 πfNaB

√2=4.44 fNaB …(2.1)

E is the sinusoidal rms or root mean square voltage of the winding,



f is the frequency in hertz,

N is the number of turns of wire on the winding,

a is the cross-sectional area of the core in square meters

B is the peak magnetic flux density in Tesla

P is the power in volt amperes or watts,

NECESSITY FOR PROTECTION

Transformers are static devices, totally enclosed and generally oil immersed. Therefore,

chances of faults occurring on them are very rare. However, the consequences of even a rare

fault may be very serious unless the transformer is quickly disconnected from the system. This

necessitates providing adequate automatic protection for transformers against possible faults.

COMMON TRANSFORMER FAULTS

As compared with generators, in which many abnormal conditions may arise, power

transformers may suffer only from:

1. Open circuits

2. Overheating

3. Winding short-circuits

Open circuit Faults:

An open circuit in one phase of a 3-phase transformer may cause undesirable heating. In

practice, relay protection is not provided against open circuits because this condition is relatively

harmless. On the occurrence of such a fault, the transformer can be disconnected manually from

the system.

Overheating Faults:

Overheating of the transformer is usually caused by sustained overloads or short circuits

and very occasionally by the failure of the cooling system. The relay protection is also not

provided against this contingency and thermal accessories are generally used to sound an alarm

or control the banks of fans.



Winding Short-circuit Faults:

Winding short-circuits (also called internal faults) on the transformer arise from

deterioration of winding insulation due to overheating or mechanical injury. When an internal

fault occurs, the transformer must be disconnected quickly from the system because a prolonged

arc in the transformer may cause oil fire. Therefore, relay protection is absolutely necessary for

internal faults.



MICROCONTROLLER

4.1 INTRODUCTION

Microcontroller is a microprocessor designed specifically for control applications, and is

equipped with ROM, RAM and facilities I / O on a single chip.AT89S52 is one of the family

MCS-51/52 equipped with an internal 8 Kbyte Flash EPROM (Erasable and Programmable Read

Only Memory), which allows memory to be reprogrammed.

The AT89S52 is a low-power, high-performance CMOS 8-bit microcomputer with 4Kbytes of

Flash programmable and erasable read only memory (PEROM).This device is a Single-chip 8-bit

Microcontroller and is a derivative of the 8051 microcontroller family. The instruction set is

100% compatible with the 8051 instruction set. The on-chip Flash allows the program memory

to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By

combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89S52 is a

powerful microcomputer which provides a highly-flexible and cost-effective solution to many

embedded control applications.



FEATURES OF MICROCONTROLLER

A CPU (central processing unit) 8 bits.

256 bytes of RAM (random access memory) internally.

Four ports of I/O with each consist of 8 bit.

The internal oscillator and timing circuit.

Two timers/counters 16 bits.

Five interrupt lines (two fruits and three external interrupt internal interruptions).

A serial port with full duplex UART (Universal Asynchronous Receiver Transmitter).

Able to conduct the process of multiplication, division, and Boolean.

The size of 8 Kbytes EPROM for program memory.

Maximum speed execution of instructions per cycle is 0.5 s at 24 MHz clock frequency.

If the microcontroller clock frequency used is 12 MHz, the speed is 1 s instruction

execution.

CPU (central processing unit)

This section serves to control the entire operation on the microcontroller. This unit is divided into

two parts, the control unit, or CU (Control Unit) and the arithmetic and logic unit or ALU

(Arithmetic Logic Unit) The main function control unit is to take instructions from memory

(fetch) and then translate the composition of these instructions into a simple collection of work

processes (decode), and implement instruction sequence in accordance with the steps that have

been determined the program (execute). Arithmetic and logic unit is the part that deals with

arithmetic operations like addition, subtraction, and logical data manipulation operations such as

AND, OR, and comparison.

4.2.2 INPUT/OUTPUT (I/O)

This section serves as a communication tool with a single chip device outside the system.

Consistent with the name, I / O devices can receive and provide data to / from a single chip.



There are two kinds of devices I / O is used, ie devices for serial connection UART (Universal

Asynchronous Receiver Transmitter) and device for so-called parallel relationship with the PIO

(Parallel Input Output).Both types of I / O has been available in a single chip AT89S52.

SOFTWARE

Single flakes MCS-51 family has a special programming language that is not understood by

other types of single flakes. This programming language known by the name of the assembler

language instruction has 256 devices. However, when this can be done with microcontroller

programming using C language. With the C language, microcontroller programming easier,

because the C language format will be automatically converted into assembler language with a

hex file format. Software on a microcontroller can be divided into five groups as follows:



PIN CONFIGURATION

AT89S52 microcontroller has 40 pins with a single 5 Volt power supply. The pin 40 is illustrated

as follows:

4.3.1 THE FUNCTION OF EACH PIN AT89S52

Vcc: Supply Voltage.

GND: Ground.


http://electricly.com/wp-content/uploads/2010/06/AT89S52-MICROCONTROLLER-configuration.jpg


Port 0:

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink eight

TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs.

Port 0 can also be configured to be the multiplexed low-order address/data bus during accesses

to external programmed data memory. In this mode, P0 has internal pull-ups. Port 0 also receives

the code bytes during Flash programming and outputs the code bytes during program

verification.

Port 1:

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers can

sink/ source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, port 1 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups. Port 1 also receives the low-order

address bytes during Flash programming and verification.

Port 2:



internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled

low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address

byte during fetching from external program memory and during access to external data memory

that uses 16-bit addresses (MOVX @DPTR). In this application, Port 2 uses strong internal pull-

ups when emitting 1s. During accesses to external data memory that uses 8-bit address (MOVX

@R1), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the

high-order address bits and some control signals during Flash program and verification.

Port 3:





internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled

low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of

Port 3 pin alternate Functions:

P 3.0 RXD (Serial Input Port)

P 3.1 TXD (Serial Output Port)

P 3.2 INT0 (External Interrupt 0)

P 3.3 INT1 (External Interrupt 1)

P 3.4 T0 (Timer 0 External Input)

P 3.5 T1 (Timer 1 External Input)

P 3.6 WR (External Data Memory Write Strobe)

P 3.7 RD (External Data Memory Read Strobe).

Port 3 also receives some control signals for Flash programming and programming verification.

RST: Reset Input

A high on this pin for two machine cycles while the oscillator is running resets the device. This

pin drives High for 98 oscillator periods after the Watchdog times out.

ALE/PROG:

Address Latch Enable is an output pulse for latching the low byte of the address during accesses

to external memory. This pin is also the program pulse input (PROG) during Flash programming.

In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be

used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped

during each access to external data memory. If desired, ALE operation can be disabled by setting

bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC

instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if

the Microcontroller is in external execution mode.

PSEN: Program Store Enable



It is the read strobe to external program memory. When the AT89S52 is executing code from

external program memory, PSEN is activated twice each machine cycle, except that two PSEN

activations are skipped during each access to external data memory.

EA/Vpp: External Access Enable/ Programming Enable Voltage

External Access Enable must be strapped to GND in order to enable the device to fetch code

from external program memory locations starting at 0000H up to FFFFH. Note, however, that if

lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to Vcc

for internal program executions. This pin also receives the 12-volt programming enable voltage

(Vpp) during Flash programming.

XTAL1:

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2:

It is the output from the inverting oscillator amplifier.



TIMER

Timer0: 8-bit timer/counter with 8-bit prescaler

Timer1: 16-bit timer/counter with prescaler

Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler.

Mode 0: 13-Bit Timer

Lower byte (TL0/TL1) + 5 bits of upper bytes (TH0/TH1).

Backward compatible to the 8048

Not generally used

Timer operation in Mode 0

Mode 1: 16-bit

All 16 bits of the timer (TH0/TL0, TH1,and TL1) are used.

Maximum count is 65,536

At 12 MHz, maximum interval is 65536 microseconds or 65.536

milliseconds

TF0 must be reset after each overflow

THx/TLx must be manually reloaded after each overflow.

Mode 2: 8-bit Auto Reload

Only the lower byte (TLx) is used for counting.

Upper byte (THx) holds the value to reload into TLx after and overflow.

TFx must be manually cleared.

Maximum count is 256

Maximum interval is 256 Microseconds or .256 milliseconds

INTERRUPT

Hardware interrupts were introduced as a way to avoid wasting the processor's valuable time

in polling loops, waiting for external events. They may be implemented in hardware as a distinct

system with control lines, or they may be integrated into the memory subsystem.

If implemented in hardware, an interrupt controller circuit such as the IBM PC's Programmable

Interrupt Controller (PIC) may be connected between the interrupting device and the processors



interrupt pin to multiplex several sources of interrupt onto the one or two CPU lines typically

available. If implemented as part of the memory controller, interrupts are mapped into the

system's memory address space.

Interrupts can be categorized into: maskable interrupt, non-maskable interrupt (NMI), inter-

processor interrupt (IPI), software interrupt, and spurious interrupt.

Maskable interrupt (IRQ) is a hardware interrupt that may be ignored by setting a bit in

an interrupt mask register's (IMR) bit-mask.

Non-maskable interrupt (NMI) is a hardware interrupt that lacks an associated bit-mask, so

that it can never be ignored. NMIs are often used for timers, especially watchdog timers.

Inter-processor interrupt (IPI) is a special case of interrupt that is generated by one

processor to interrupt another processor in a multiprocessor system.

Software interrupt is an interrupt generated within a processor by executing an instruction.

Software interrupts are often used to implement system calls because they implement a

subroutine call with a CPU ring level change.

Spurious interrupt is a hardware interrupt that is unwanted. They are typically generated by

system conditions such as electrical interference on an interrupt line or through incorrectly

designed hardware.

Processors typically have an internal interrupt mask which allows software to ignore all external

hardware interrupts while it is set. This mask may offer faster access than accessing an interrupt

mask register (IMR) in a PIC, or disabling interrupts in the device itself. In some cases, such as

the x86 architecture, disabling and enabling interrupts on the processor itself act as a memory

barrier, however it may actually be slower.

An interrupt that leaves the machine in a well-defined state is called a precise interrupt. Such an

interrupt has four properties:

The Program Counter (PC) is saved in a known place.

All instructions before the one pointed to by the PC have fully executed.

No instruction beyond the one pointed to by the PC has been executed (that is no prohibition

on instruction beyond that in PC, it is just that any changes they make to registers or memory

must be undone before the interrupt happens).



The execution state of the instruction pointed to by the PC is known.

An interrupt that does not meet these requirements is called an imprecise interrupt.

The phenomenon where the overall system performance is severely hindered by excessive

amounts of processing time spent handling interrupts is called an interrupt storm.

TYPES OF INTERRUPT

LEVEL-TRIGGERED

EDGE-TRIGGERED

HYBRID

MESSAGE SIGNALED

DOORBELL

USES OF INTERRUPT

Typical uses of interrupts include the following: system timers, disks I/O, power-off signals,

and traps. Other interrupts exist to transfer data bytes using UARTs or Ethernet; sense key-

presses; control motors; or anything else the equipment must do.

A classic system timer generates interrupts periodically from a counter or the power-line. The

interrupt handler counts the interrupts to keep time. The timer interrupt may also be used by the

OS's task scheduler to reschedule the priorities of running processes. Counters are popular, but

some older computers used the power line frequency instead, because power companies in most

Western countries control the power-line frequency with a very accurate atomic clock.

A disk interrupt signals the completion of a data transfer from or to the disk peripheral. A

process waiting to read or write a file starts up again.

A power-off interrupt predicts or requests a loss of power. It allows the computer equipment to

perform an orderly shut-down.

Interrupts are also used in type ahead features for buffering events like keystrokes.

NEED OF MICROCONTROLLER



Microcontroller is a general-purpose device which has in-built CPU memory and

peripherals to make it act as a mini-computer

Microcontroller has one or two operational codes for moving data from external to CPU

Microcontroller has many bit handling instructions

Microcontroller works faster than microprocessor because of rapid movement of bits

within the chip

Microcontroller can function as a computer with the addition of no external parts



POWER SUPPLY

INTRODUCTION

A power supply is a device that supplies electrical energy to one or more electric loads. The term

is most commonly applied to devices that convert one form of electrical energy to another,

though it may also refer to devices that convert another form of energy (e.g., mechanical,

chemical, solar) to electrical energy. A regulated power supply is one that controls the output

voltage or current to a specific value; the controlled value is held nearly constant despite

variations in either load current or the voltage supplied by the power supply's energy source.

Every power supply must obtain the energy it supplies to its load, as well as any energy it

consumes while performing that task, from an energy source. Depending on its design, a power

supply may obtain energy from:

Electrical energy transmission systems. Common examples of this include power supplies

that convert AC line voltage to DC voltage.

Energy storage devices such as batteries and fuel cells.

Electromechanical systems such as generators and alternators.

Solar power.

A power supply may be implemented as a discrete, stand-alone device or as an integral device

that is hardwired to its load. Examples of the latter case include the low voltage DC power

supplies that are part of desktop computers and consumer electronics devices.

The amount of voltage and current it can supply to its load.

How stable its output voltage or current is under varying line and load conditions.

How long it can supply energy without refueling or recharging (applies to power supplies

that employ portable energy sources)

.



EXPLAINATION AND BLOCK DIAGRAM

The ac voltage, typically 220V rms, is connected to a transformer, which steps that ac

voltage down to the level of the desired dc output. A diode rectifier then provides a full-

wave rectified voltage that is initially filtered by a simple capacitor filter to produce a dc

voltage. This resulting dc voltage usually has some ripple or ac voltage variation.

A regulator circuit removes the ripples and also remains the same dc value even if the input

dc voltage varies, or the load connected to the output dc voltage changes. This voltage

regulation is usually obtained using one of the popular voltage regulator IC units.

POWER SUPPLY


Regulator

Filter

Bridge Rectifier

Step down transformer

230V AC

50Hz

D.C Output


CIRCUIT DIAGRAM OF POWER SUPPLY

WORKING OF POWER SUPLLY



TRANSFORMER:

Usually, DC voltages are required to operate various electronic equipment and these voltages are

5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input available at the

mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a

transformer. Thus, a step down transformer is employed to decrease the voltage to a required

level.

RECTIFIER:

The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The

rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used

because of its merits like good stability and full wave rectification.

FILTER:

Capacitive filter is used in this project. It removes the ripples from the output of rectifier and

smoothens the D.C. Output received from this filter is constant until the mains voltage and load

is maintained constant. However, if either of the two is varied, D.C. voltage received at this point

changes. Therefore a regulator is applied at the output stage.

VOLTAGE REGULATOR:

As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical

regulator designed to automatically maintain a constant voltage level. In this project, power

supply of 5V and 12V are required. In order to obtain these voltage levels, 7805 and 7812

voltage regulators are to be used. The first number 78 represents positive supply and the numbers

05, 12 represent the required output voltage levels.



5.5 POWER SUPPLY APPLICATION

5.5.1 Computer power supply

A modern computer power supply is a switch-mode power supply that converts AC power from

the mains supply, to several DC voltages. Switch-mode supplies replaced linear supplies due to

cost, weight, and size improvement. The diverse collection of output voltages also has widely

varying current draw requirements.

5.5.2 Welding power supply

Arc welding uses electricity to melt the surfaces of the metals in order to join them together

through coalescence. The electricity is provided by a welding power supply, and can either

be AC or DC. Arc welding typically requires high currents typically between 100 and 350 amps.

Some types of welding can use as few as 10 amps, while some applications of spot

welding employ currents as high as 60,000 amps for an extremely short time. Older welding

power supplies consisted of transformers or engines driving generators. More recent supplies

use semiconductors and microprocessors reducing their size and weight.

5.5.3 AC Adapter

A power supply that is built into an AC mains power plug is known as a "plug pack" or "plug-in

adapter", or by slang terms such as "wall wart". They are even more diverse than their names;

often with either the same kind of DC plug offering different voltage or polarity, or a different

plug offering the same voltage. "Universal" adapters attempt to replace missing or damaged

ones, using multiple plugs and selectors for different voltages and polarities. Re5lacement power

supplies must match the voltage of, and supply at least as much current as, the original power

supply.





LIQUID CRYSTAL DISPLAY

LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of

applications. A 16x2 LCD display is very basic module and is very commonly used in various

devices and circuits. These modules are preferred over seven segment and other multi

segment LEDs. The reasons being: LCDs are economical; easily programmable; have no

limitation of displaying special & even custom characters (unlike in seven

segments), animations and so on.

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD

each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command

and Data.

The command register stores the command instructions given to the LCD. A command is an

instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting the

cursor position, controlling display etc. The data register stores the data to be displayed on the

LCD. The data is the ASCII value of the character to be displayed on the LCD.

LCDs are used in a wide range of applications, including computer monitors, television,

instrument panels, aircraft cockpit displays, signage, etc. They are common in consumer devices

such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have

replaced cathode ray tube (CRT) displays in most applications. They are available in a wider

range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they

cannot suffer image burn-in. LCDs are, however, susceptible to image persistence.

The LCD is more energy efficient and offers safer disposal than a CRT. Its low electrical power

consumption enables it to be used in battery-powered electronic equipment. It is an electronically

modulated optical device made up of any number of segments filled with liquid crystals and

arrayed in front of a light source (backlight) or reflector to produce images in color

or monochrome. The most flexible ones use an array of small pixels. The earliest discovery

leading to the development of LCD technology, the discovery of liquid crystals, dates from 1888.

By 2008, worldwide sales of televisions with LCD screens had surpassed the sale of CRT units.



6.2 FEATURES

5 x 8 dots with cursor

Built-in controller (KS 0066 or equivalent)

+5V power supply (also available for +3V)

1/16 duty cycle

B/L to be driven 1,pin 2 or pin 15,pin 16

N.V. optional for +3V power supply

LCD can display a character successfully by placing the

1. Data in Data Register

2. Command in Command Register of LCD

3. Data corresponds to the ASCII value of the character to be printed. This can be done by

placing the ASCII value on the LCD Data lines and selecting the Data Register of the

LCD by selecting the RS (Register Select) pin.

4. Each and every display location is accessed and controlled by placing respective command on

the data lines and selecting the Command Register of LCD by selecting the (Register Select) RS

pin.

TABLE 1: Pin description for LCD




Pin symbol I/O Description

1 Vss -- Ground

2 Vcc -- +5V power supply

3 VEE -- Power supply to

control contrast

4 RS I RS=0 to select

command register

RS=1 to select

data register

5 R/W I R/W=0 for write

R/W=1 for read

6 E I/O Enable

7 DB0 I/O The 8-bit data bus









TYPES OF DISPLAY LCD:

Segment (or alphanumeric)

Dot matrix (or character)

Graphic LCD.

Advantages and disadvantages of LCDs

In spite of LCDs being a well proven and still viable technology, as display devices LCDs are

not perfect for all applications.

6.5.1 Advantages

Very compact and light.

Low power consumption.

No geometric distortion.

Little or no flicker depending on backlight technology.

Not affected by screen burn-in.

Can be made in almost any size or shape.

No theoretical resolution limit.

6.5.2 Disadvantages

Limited viewing angle, causing color, saturation, contrast and brightness to vary, even

within the intended viewing angle, by variations in posture.

Bleeding and uneven backlighting in some monitors, causing brightness distortion,

especially toward the edges.

Smearing and ghosting artifacts caused by slow response times (>8 ms) and "sample and

hold" operation.

Only one native resolution. Displaying resolutions either requires a video scaler, lowering

perceptual quality, or display at 1:1 pixel mapping, in which images will be physically

too large or won't fill the whole screen.



Fixed bit depth, many cheaper LCDs are only able to display 262,000 colors. 8-bit S-IPS

panels can display 16 million colors and have significantly better black level, but are

expensive and have slower response time.

Low bit depth results in images with unnatural or excessive contrast.

Input lag

Dead or stuck pixels may occur during manufacturing or through use.

In a constant-on situation, thermalization may occur, which is when only part of the

screen has overheated and looks discolored compared to the rest of the screen.

Not all LCDs are designed to allow easy replacement of the backlight.

Cannot be used with light guns/pens.

Loss of contrast in high temperature environments.

6.6 MAX 232

max 232 circuit diagram



Since the RS232 (Recommended Standard) is not compatible with today’s microprocessor and

microcontrollers, we need a line driver to convert the RS232’s signal to TTL voltage levels that

will be acceptable to the AT89C51 TXD and RXD pins.

One example of such a converter is MAX 232. MAX 232 converts from Rs232 voltage levels to

TTL voltage levels, and vice versa. One advantages of the MAX232 chip is that it uses a +5v

power source which ,is the same as the source voltages for the 89C52.

In other words with a single +5v power supply we can power both the AT89C51 and MAX232,

with no need for the dual power supply that are common in many older systems. The MAX232

has 2 sets of line drivers for transferring and receiving data, as shown the line drivers used for

TXD are called T1 and T2, while the line drives for RXD are designated as R1 and R2.

The MAX232 is an integrated circuit that converts signals from an RS-232 serial port to signals

suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver

and typically converts the RX, TX, CTS and RTS signals.

The drivers provide RS-232 voltage level outputs (approx. ± 7.5 V) from a single + 5 V supply

via on-chip charge pumps and external capacitors. This makes it useful for implementing RS-232

in devices that otherwise do not need any voltages outside the 0 V to + 5 V range, as power

supply design does not need to be made more complicated just for driving the RS-232 in this

case.

The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to standard

5 V TTL levels. These receivers have a typical threshold of 1.3 V, and a typical hysteresis of

0.5 V.

The later MAX232A is backwards compatible with the original MAX232 but may operate at

higher baud rates and can use smaller external capacitors – 0.1 μF in place of the 1.0 μF

capacitors used with the original device. The newer MAX3232 is also backwards compatible, but

operates at a broader voltage range, from 3 to 5.5 V.


http://en.wikipedia.org/wiki/Farad

http://en.wikipedia.org/wiki/Baud

http://en.wikipedia.org/wiki/Hysteresis

http://en.wikipedia.org/wiki/Transistor-transistor_logic

http://en.wikipedia.org/wiki/Power_supply

http://en.wikipedia.org/wiki/Power_supply

http://en.wikipedia.org/wiki/Charge_pump

http://en.wikipedia.org/wiki/Transistor-transistor_logic

http://en.wikipedia.org/wiki/RS-232

http://en.wikipedia.org/wiki/Integrated_circuit


GSM

7.1 INTRODUCTION

GSM (Global System for Mobile Communications: originally from Groupe Special Mobile) is

the world's most popular standard for mobile telephony systems. The GSM Association estimates

that 80% of the global mobile market uses the standard. GSM is used by over 1.5

billion people across more than 212 countries and territories. This ubiquity means that

subscribers can use their phones throughout the world, enabled by

international roaming arrangements between mobile network operators. GSM differs from its

predecessor technologies in that both signalling and speech channels are digital, and thus GSM is

considered a second generation (2G) mobile phone system. This also facilitates the wide-spread

implementation of data communication applications into the system.

The GSM standard has been an advantage to both consumers, who may benefit from the ability

to roam and switch carriers without replacing phones, and also to network operators, who can

choose equipment from many GSM equipment vendors. GSM also pioneered low-cost

implementation of the short message service (SMS), also called text messaging, which has since

been supported on other mobile phone standards as well. The standard includes a

worldwide emergency telephone number feature.

Newer versions of the standard were backward-compatible with the original GSM system. For

example, Release '97 of the standard added packet data capabilities by means of General Packet

Radio Service (GPRS). Release '99 introduced higher speed data transmission using Enhanced

Data Rates for GSM Evolution (EDGE).


http://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolution

http://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolution

http://en.wikipedia.org/wiki/General_Packet_Radio_Service

http://en.wikipedia.org/wiki/General_Packet_Radio_Service

http://en.wikipedia.org/wiki/3GPP#Standards

http://en.wikipedia.org/wiki/Emergency_telephone_number

http://en.wikipedia.org/wiki/Short_message_service

http://en.wikipedia.org/wiki/2G

http://en.wikipedia.org/wiki/Digital

http://en.wikipedia.org/wiki/Mobile_network_operator

http://en.wikipedia.org/wiki/Roaming

http://en.wikipedia.org/wiki/1000000000_(number)

http://en.wikipedia.org/wiki/GSM_Association

http://en.wikipedia.org/wiki/Mobile_telephony

http://en.wikipedia.org/wiki/Comparison_of_mobile_phone_standards


7.2 THE CELLULAR NETWORK

GSM REFERENCE MODEL

MS

The MS consist of physical equipment used by the subscriber to access a PLMN for offered

telecommunication services. The MS includes a Mobile Terminal and depending on the services

it can support various Terminal Equipment(TE).Various type of MS, such as vehicle mounted

station, portable station, or handheld station, are used.

The MSs come in five power classes which define the maximum RF power level that the unit

can transmit. Basically, an MS can be divided into two parts. The first part contains the hardware

and software to support radio and human interface functions. The second part contains



terminal/user-specific data in the form of a smart card, which can effectively be considered a sort

of logical terminal. The SIM card plugs into the first part of the MS and remains in for the

duration of use. Without the SIM card, the MS is not associated with any user and cannot make

or receive calls (except possibly an emergency cal l if the network allows). The SIM card is

issued by the mobile service provider after subscription, while the first part of the MS would be

available at retail shops to buy orrent. This type of SIM card mobility is analogous to terminal

mobility, but provides a personal-mobility-like service within the GSM mobile network.

IMSI

The IMSI is assigned to an MS at subscription time. It uniquely identifies a given MS. The IMSI

will be transmitted over the radio interface only if necessary. The IMSI contains 15 digits and

includes

Mobile Country Code (MCC)—3 digits (home country)

Mobile Network Code (MNC)—2 digits (home GSM PLMN)

Mobile Subscriber Identification (MSIN)

National Mobile Subscriber Identity (NMSI)

TEMPORARY MOBILE SUBSCRIBER IDENTITY (TMSI )

The TMSI is assigned to an MS by the VLR. The MSI uniquely identifies an MS within the

area controlled by a given VLR. The maximum number of bits that can be used for the TMSI is

32

.

IMEI

The IMEI uniquely identifies the MS equipment. It is assigned by the equipment manufacturer.

The IMEI contains 15 digits and carries



The Type Approval Code (TAC)—6 digits

The Final Assembly Code (FAC)—2 digits

The serial number (SN)— 6 digits

A Spare (SP)—1 digit

SIM

The SIM carries the following information

IMSI

Authentication Key (Ki)

Subscriber information

Access control class

Cipher Key (Kc)

TMSI

Additional GSM services

Location Area Identity (LAI)

Forbidden PLMN

BSS

The BSS is the physical equipment that provides radio coverage to prescribed geographical

areas, known as the cells. It contains equipment required to communicate with the MS.

Functionally, a BSS consists of a control function carried out by the BSC and a transmitting

function performed by the BTS. The BTS is the radio transmission equipment and covers each

cell. A BSS can serve several cells because it can have multiple BTSs.The BTS contains the

Transcoder Rate Adapter Unit (TRAU). In TRAU, the GSM-specific speech encoding and

decoding is carried out, as well as the rate adaptation function for data. In certain situations the

TRAU is located at the MSC to gain an advantage of more compressed transmission between the

BTS and the MSC



NSS

The NSS includes the main switching functions of GSM, databases required for the subscribers,

and mobility management. Its main role is to manage the communi cat ions between GSM and

other network users.Within the NSS, the switching functions are performed by the MSC.

Subscriber information relevant to provisioning of services is kept in the HLR. The other

database in the NSS is the VLR. The MSC performs the necessary switching functions required

for the MSs located in an associated geographical area, called an MSC area. The MSC monitors

the mobility of its subscribers and manages necessary resources required to handle and update

the location registration procedures and to carry out the handover functions. The MSC is

involved in the interworking functions to communicate with other networks such as PSTN and

ISDN. The interworking functions of the MSC depend upon the type of the network to which it

is connected and the type of service to be performed. The call routing and control and echo

control functions are also performed by the MSC.

The HLR is the functional unit used for management of mobile subscribers. The number of

HLRs in a PLMN varies with the characteristics of the PLMN. Two types of information are

stored in the HLR: subscriber information and part of the mobile information to allow incoming

calls to be routed to the MSC for the particular MS. Any administrative action by the service

provider on subscriber data is performed in the HLR. The HLR stores IMSI, MS ISDN number,

VLR address, and subscriber data (e.g., supplementary services).

The VLR is linked to one or more MSCs. The VLR is the functional unit that dynamically stores

subscriber information when the subscriber is located in the area covered by the VLR. When a

roaming MS enters an MSC area, the MSC informs the associated VLR about the MS the

MS goes through a registration procedure. The registration procedure for the MSincludes these

activities:

The VLR recognizes that the MS is from another PLMN.



If roaming is allowed, the VLR finds the MS’s HLR in its home PLMN.

The VLR constructs a Global Title (GT) from the IMSI to allow signaling from the VLR

to the MS’s HLR via the PSTN/ISDN networks.

The VLR generates a Mobile Subscriber Roaming Number (MSRN) thatis used to route

incoming calls to the MS.

The MSRN is sent to the MS’s HLR.



ZIGBEE

ZigBee is a low-cost, low-power, wireless mesh network standard. The low cost allows the

technology to be widely deployed in wireless control and monitoring applications. Low power-

usage allows longer life with smaller batteries. Mesh networking provides high reliability and

more extensive range. ZigBee chip vendors typically sell integrated radios and microcontrollers

with between 60 KB and 256 KB flash memory.

ZigBee operates in the industrial, scientific and medical (ISM) radio bands; 868 MHz in Europe,

915 MHz in the USA and Australia, and 2.4 GHz in most jurisdictions worldwide. Data

transmission rates vary from 20 to 900 kilobits/second.

The ZigBee network layer natively supports both star and tree typical networks, and generic

mesh networks. Every network must have one coordinator device, tasked with its creation, the

control of its parameters and basic maintenance.

TYPES OF ZIGBEE DEVICE

Zigbee devices are of three types:

ZigBee coordinator (ZC): The most capable device, the coordinator forms the root of the

network tree and might bridge to other networks. There is exactly one ZigBee coordinator in

each network since it is the device that started the network originally. It stores information

about the network, including acting as the Trust Center & repository for security keys.

ZigBee Router (ZR): As well as running an application function, a router can act as an

intermediate router, passing on data from other devices.



ZigBee End Device (ZED): Contains just enough functionality to talk to the parent node

(either the coordinator or a router); it cannot relay data from other devices. This relationship

allows the node to be asleep a significant amount of the time thereby giving long battery life.

A ZED requires the least amount of memory, and therefore can be less expensive to

manufacture than a ZR or ZC.

USES OF ZIGBEE

ZigBee protocols are intended for embedded applications requiring low data rates and low power

consumption. The resulting network will use very small amounts of power — individual devices

must have a battery life of at least two years to pass ZigBee certification.

Typical application areas include:

Home Entertainment and Control — Home automation, smart lighting, advanced

temperature control, safety and security, movies and music

Wireless Sensor Networks — Starting with individual sensors like Telosb/Tmote and Iris

from Memsic

Industrial control

Embedded sensing

Medical data collection

Smoke and intruder warning

Building automation

8.2 PIEZO BUZZER

A buzzer or beeper is an audio signaling device, which may be mechanical, electromechanical,

or piezoelectric. Typical uses of buzzers and beepers include alarm devices, timers and

confirmation of user input such as a mouse click or keystroke.

The piezo buzzer produces sound based on reverse of the piezoelectric effect. The generation of

pressure variation or strain by the application of electric potential across a piezoelectric material



is the underlying principle. These buzzers can be used alert a user of an event corresponding to a

switching action, counter signal or sensor input. They are also used in alarm circuits.

The buzzer produces a same noisy sound irrespective of the voltage variation applied to it. It

consists of piezo crystals between two conductors. When a potential is applied across these

crystals, they push on one conductor and pull on the other. This, push and pull action, results in a

sound wave. Most buzzers produce sound in the range of 2 to 4 kHz.

The Red lead is connected to the Input and the Black lead is connected to Ground.

CIRCUIT DIAGRAM OF BUZZER

This buzzer is an piezo type audio signaling device, which has a piezo element and a oscillating

circuit inside which oscillates the piezo brass base plate, which when given voltage difference

produces sound of a predefined frequency. You must be aware of such sounds of buzzer like

BEEP sound in many appliances.



INTERFACING

INTERFACING 16x2 LCD WITH MICROCONTROLLER

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD

each character is displayed in 5x7 pixel matrix. This LCD has two registers.

1. Command/Instruction Register- stores the command instructions given to the LCD. A

command is an instruction given to LCD to do a predefined task like initializing, clearing the

screen, setting the cursor position, controlling display etc.

2. Data Register- stores the data to be displayed on the LCD. The data is the ASCII value of the

character to be displayed on the LCD.

Commonly used LCD Command codes:

Hex Code

Command to LCD Instruction Register

1 Clear screen display2 Return home4 Decrement cursor



6 Increment cursorE Display ON, Cursor ON

80 Force the cursor to the beginning of the 1st lineC0 Force cursor to the beginning of the 2nd line38 Use 2 lines and 5x7 matrix

The pin description of this module is given below:

Pin configuration :

Pin Symbol Description

1 VSS Ground 0 V

2 VCC Main power supply +5 V

3 VEE Power supply to control contrast Contrast adjustment by providing a

variable resistor through VCC

4 RS Register Select

RS=0 to select Command Register

RS=1 to select Data Register

5 R/W Read/write

R/W=0 to write to the register

R/W=1 to read from the register

6 EN Enable A high to low pulse (minimum

450ns wide) is given when data is

sent to data pins

7 DB0

To display letters or numbers, their

ASCII codes are sent to data pins

(with RS=1). Also instruction

command codes are sent to these

pins.

8 DB1

9 DB2

10 DB3 8-bit data pins

11 DB4

12 DB5

13 DB6

14 DB7

15 Led+ Backlight VCC +5 V



16 Led- Backlight Ground 0 V

INTERFACING GSM MODULE WITH MICROCONTROLLER

GSM is widely used mobile communication architecture used in most of the countries. This

project demonstrates the interfacing of microcontrollerAT89S52 with HyperTerminal and GSM

module. It aims to familiarize with the syntax of AT Commands and their Information Response

and Result Codes. The ASCII values of characters in the Information Response, Result Codes

and their syntax can be monitored by an LED array. For the basic concepts, working and

operation of AT commands and GSM module refer GSM/GPRS Module.

A GSM module has an RS232 interface for serial communication with an external peripheral. In

this case, the transmit pin (Tx) of the computer’s Serial port is connected with the receive pin

(Rx) of the GSM module’s RS-232 interface. The transmit pin (Tx) of the RS-232 of GSM

module is connected to receive pin (Rx) of microcontroller’s serial transmission pin. And the

serial transmit pin of the microcontroller is connected to the receive pin of the computer’s Serial

port.



SOFTWARE USED

INTRODUCTION TO EMBEDDED ‘C’:

Embedded is the extension of c language. Embedded C is a compiler which constitutes more

build in function. By using c language it is easy to connect the comport easily. The embedded c

compiler has the bias function to connect the comport. The command from fussing kit sends

from the c program according to user wish.

HI-TEC ‘C’

HI-TEC ‘C’ is a set of software that translates the program written in the C language in to

executable machine code versions are available which compile the program for the operation

under the host operating system.

Some of the Hi-Tec features are

A simple batch file will compile, assemble and link entire program

The compiler perform strong type checking and issues warning about various constructs

which may represent programming errors

The generated code is extremely small and fast in execution

A full run time library is provided implementing all standard c input/ output and other

function

The source code for all run time routine is provided

A power full general purpose macro-assembler is provided

Programs may be generated to execute under the host operating system or customized

for installation in ROM.



PROBLEMS RESOLVED BY THE SYSTEM:

Early detection of failures in electric power transformers can be succeeded with

neural modeling and the Local Statistical Approach to Fault Diagnosis

• Neuro-fuzzy networks are proposed for modeling the dynamics of a critical parameter

of the power transformer known as Hot Spot Temperature.

• The output of the neural-fuzzy network is compared to the output of the exact model

(Representing the fault-free condition of the transformer) and residuals are generated

• The residuals undergo statistical signal processing according to a fault detection

and isolation algorithm (Local Statistical Approach to FDI)

• The Local Statistical Approach consists of the global test for fault detection and

of the sensitivity and min-max tests for fault isolation

• If a fault threshold defined by the FDI algorithm is exceeded then deviation from

normal operation can be detected at its early stages and an alarm can be launched

• The proposed FDI approach can be applied to other components of the power grid,

e.g power generators, etc.

ADVANTAGES:

Detecting signs of failure conditions

Reducing probability of catastrophic failure

Reducing unscheduled outages

Addressing specific unit or population issues

Loading T&D equipment for maximum efficiency

Deferring upgrade capital costs

Managing & extending the life of equipment

Reducing Observation & Measurement costs.

CONCLUSION



Transformers are static devices, totally enclosed and generally oil immersed. Therefore chances

of faults occurring on them are very rare. However the consequences of even a rare fault may be

very serious unless the transformer is quickly disconnected from the system. This necessitates to

provide adequate automatic protection for transformers against possible faults. The major faults

on transformers occur due to short circuits in the transformers or in their connections. The basic

system used for protection against these faults is the differential relay Protection of power

transformer is a big challenge nowadays. By the help of microcontroller-based relay, protection

of transformer is performed very quickly and accurately. This system provides a better and safer

protection than the other methods which are currently in use. The advantages of this system over

the current methods in use are fast response, better isolation and accurate detection of the fault.

This system overcomes the other drawbacks in the existing systems such as maintenance and

response time.


Documents

Transformer Fault Detection Using Zigbee and GSM