OVERHEAD LINE BROKEN CONDUCTOR DETECTION

CHAPTER 1INTRODUCTION

1.1 EMBEDDED SYSTEMS

Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real time performance constraints that must be met, for reason such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs.Anembedded systemis not always a separate block - very often it is physically built-in to the device it is controlling. The software written for embedded systems is often calledfirmware, and is stored in read-only memory or flash convector chips rather than a disk drive. It often runs with limited computer hardware resources: small or no keyboard, screen, and little memory. Wireless communication has become an important feature for commercialproductsand a popular research topic within the last ten years. There are now more mobile phone subscriptions than wired-line subscriptions. Lately, one area of commercial interest has been low-cost, low-power, and short-distance wireless communication used for personal wireless networks." Technology advancements are providing smaller and more cost effective devices for integrating computational processing, wireless communication, and a host of other functionalities. These embedded communications devices will be integrated into applications ranging from homeland security to industry automation andmonitoring. They will also enable custom tailored engineering solutions, creating a revolutionary way of disseminating and processing information. With new technologies and devices comenew businessactivities, and the need for employees in these technological areas. Engineers who have knowledge of embedded systems and wireless communications will be in high demand. Unfortunately, there are few adorable environments available for development and classroom use, so students often do not learn about these technologies during hands-on lab exercises. The communication mediums were twisted pair, optical fiber, infrared, and generally wireless radio.

ABSTRACTOverhead line distribution system is generally used in rural area with a free space. In case of broken conductor, the pedestrian may be injured from high-voltage conductor, if the system cannot detect and make a command to open the circuit breaker. In this paper, we apply the principle of time shifting to detect the broken line conductor on the source side with a variation of fault impedance compared with the ratio of negative to positive sequence current. When the fault is detected the Microcontroller Operates the Relay Device. The Protective alarm is connected to Relay and Intimates the Broken Conductor Information and Fault Information. The studied results were taken from the Project Demo Kit and the Results are found Satisfactory

CHAPTER 2

LITERATURE REVIEW

1. Service-oriented Advanced Metering Infrastructure for Smart Grids

AbstractAdvanced Metering Infrastructure (AMI) enables smart grids to involve power consumers in the business process of power generation, transmission, distribution and consumption. However, the participant of consumers challenges the current power systems with system integration and cooperation and security issues. In this paper, we introduce a service-oriented approach to AMI aiming at solving the intercommunication problem and meanwhile providing a trust and secure environment for smart grids. In this approach heterogeneous systems expose services to the network. System integration and cooperation are done through service composition. A generic service interfacing method is designed to develop standardized services for heterogeneous power systems. Moreover, role-based access control mechanism is used to guarantee the secure access to smart grids.

2. Functional Analysis of Advanced Metering Infrastructure in Smart Grid

Abstract-Today, smart grid has been widely discussed in worldwide. As advanced metering infrastructure is one of main technologies of smart grid, its structure and functions of each component is represented. In terms of basic features of smart grid, some key capabilities that advanced metering infrastructure should possess are analyzed, and its impacts on power grid networks as well. Combining current research situation of power utility information acquisition system in china, this paper provides reference for building smart grid of user side on the basis of these preliminary analyses.

3. Improvement of the Short Term Load Forecasting Through the Similarity Among Consumption Profiles

Abstract In order to achieve high quality standards in electrical power systems, utility companies rely upon load forecasting to accomplish critical activities such as optimal dynamic dispatch and smart performance in the power wholesale market. Several works propose hybrid intelligent forecasting models to deal with the dynamic and nonlinear characteristics of the load at a relatively high computational cost. While such approaches give emphasis to the forecasting itself, this paper presents a procedure to detect similarities among distinct consumption profiles. Empirical results show that similar profile share similar sets of relevant predictors. As finding similarities among profiles is less costly than finding the set of relevant predictors from scratch, a new parameter selection method is proposed. Such method is employed to build some neural forecasters with a marked improvement in the learning time.

4. Data Collecting from Smart Meters in an Advanced Metering Infrastructure

Abstract The classical solution for collecting data from energy meters, based on displacements of peoples, tends to be replaced by modern solutions: drive-by and Automated Meter Reading (AMR). AMR means to automatically collectdata from meters and send them to a central computer. An Advanced Metering Infrastructure (AMI) is an AMR infrastructure with bidirectional smart meters gateway communication, this leading to extra facilities. CHAPTER 3

4.1 BLOCK DIAGRAM

4.2 BLOCK DIAGRAM DESCRIPTION

BLOCK DIAGRAM EXPLANATION:The above block diagram gives the overview of theprojectin the pictorial form with the help of the block diagram we will create pre model of theprojectand analyze the function of theprojectthe explanation of theprojectwith block diagram over view is given as follows.BLOCK DESCRIPTION

Power Supply Section:

This section is meant for supplying Power to all the sections mentioned above. It basically consists of a Transformer to step down the 230V ac to 18V ac followed by diodes. Here diodes are used to rectify the ac to dc. After rectification the obtained rippled dc is filtered using a capacitor Filter. A positive voltage regulator is used to regulate the obtained dc voltage.

Microcontroller Section:This section forms the control unit of the wholeproject. This section basically consists of a Microcontroller with its associated circuitry like Crystal with capacitors, Reset circuitry, Pull up resistors (if needed) and so on. The Microcontroller forms the heart of theprojectbecause it controls the devices being interfaced and communicates with the devices according to the program being written.Transformers: In general, the ac line voltage presentin your housewiring is not suitable for electronic circuits. Most circuits require a considerably lower voltage, while a few require higher voltages. The transformer serves to convert the ac line voltage to a voltage level more appropriate to the needs of the circuit to be powered. At the same time, the transformer provides electrical isolation between the ac line and the circuit being powered, which is an important safety consideration. However, a line transformer is generally large and heavy, and is rather expensive. Therefore, some power supplies (notably for PCs) are deliberately designed to operate directly from the ac line without a line transformer. The output of the transformer is still an ac voltage, but now of an appropriate magnitude for the circuit to be powered.

ADC: Analog to digital (A/D, ADC) converters are electrical circuit devices that convert continuous signals, such as voltages or currents, from the analog domain to the digital domain where the signals are represented by numbers.LCD Display Section: This section is basically meant to show upthe statusof theproject. Thisprojectmakes use of Liquid Crystal Display to display / prompt for necessary information. Sensors: This part of the system consists of current sensor. These sensor sense various parameters of load- current and are then sent to the Analog to Digital Converter.Relay: In thisprojectRelays are used to the Trip the transformer. A relay is an electrical switch that opens and closes under control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contactsCHAPTER 5

HARDWARE:

POWER SUPPLY:

Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others.

A 230v, 50Hz Single phase AC power supply is given to a step down transformer to get 12v supply. This voltage is converted to DC voltage using a Bridge Rectifier. The converted pulsating DC voltage is filtered by a 2200uf capacitor and then given to 7805 voltage regulator to obtain constant 5v supply. This 5v supply is given to all the components in the circuit. A RC time constant circuit is added to discharge all the capacitors quickly. To ensure the power supply a LED is connected for indication purpose.

power supply:

definition:

A power supply (sometimes known as a power supply unit or PSU) is a device or system that supplies electrical or other types of energy to an output load or group of loads. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others.

Figure A.Block diagram of a basic power supply.

As illustrated in view B of figure, the first section is the TRANSFORMER.

The transformer steps up or steps down the input line voltage and isolates the power supply from the power line.

The RECTIFIER section converts the alternating current input signal to a pulsating direct current. However, as you proceed in this chapter you will learn that pulsating dc is not desirable. For this reason a FILTER section is used to convert pulsating dc to a purer, more desirable form of dc voltage.

Figure B.Block diagram of a basic power supply. The final section, the REGULATOR, does just what the name implies. It maintains the output of the power supply at a constant level in spite of large changes in load current or input line voltages. Now that you know what each section does, let's trace an ac signal through the power supply. At this point you need to see how this signal is altered within each section of the power supply. Later on in the chapter you will see how these changes take place. In view B of figure 4-1, an input signal of 115 volts ac is applied to the primary of the transformer.

The transformer is a step-up transformer with a turns ratio of 1:3. You can calculate the output for this transformer by multiplying the input voltage by the ratio of turns in the primary to the ratio of turns in the secondary; therefore, 115 volts ac 3 = 345 volts ac (peak-to- peak) at the output. Because each diode in the rectifier section conducts for 180 degrees of the 360-degree input, the output of the rectifier will be one-half, or approximately 173 volts of pulsating dc. The filter section, a network of resistors, capacitors, or inductors, controls the rise and fall time of the varying signal; consequently, the signal remains at a more constant dc level. You will see the filter process more clearly in the discussion of the actual filter circuits. The output of the filter is a signal of 110 volts dc, with ac ripple riding on the dc. The reason for the lower voltage (average voltage) will be explained later in this chapter. The regulator maintains its output at a constant 110-volt dc level, which is used by the electronic equipment (more commonly called the load). Simple 5V power supply for digital circuits

1.1 Summary of circuit features Brief description of operation: Gives out well regulated +5V output, output current capability of 100 mA

Circuit protection: Built-in overheating protection shuts down output when regulator IC gets too hot

Circuit complexity: Very simple and easy to build

Circuit performance: Very stable +5V output voltage, reliable operation

Availability of components: Easy to get, uses only very common basic components

Design testing: Based on datasheet example circuit, I have used this circuit successfully as part of many electronics projects

Applications: Part of electronics devices, small laboratory power supply

Power supply voltage: Unregulated DC 8-18V power supply

Power supply current: Needed output current + 5 mA

Component costs: Few dollars for the electronics components + the input transformer cost

5.1 ATMEGA 8 5.1.1 CONCEPTS OF MICROCONTROLLER: Microcontroller is a general purpose device, which integrates a number of the components of a microprocessor system on to single chip. It has inbuilt CPU, memory and peripherals to make it as a mini computer. A microcontroller combines on to the same microchip:

The CPU core

Memory(both ROM and RAM)

Some parallel digital i/o

Micro controllers will combine other devices such as:

A timer module to allow the micro controller to perform tasks for certain time periods.

A serial i/o port to allow data to flow between the controller and other devices such as a PIC or another Microcontroller.

An ADC to allow the Micro controller to accept analogue input data for processing.

Micro controllers are :

Smaller in size

Consumes less power

Inexpensive

Micro controller is a stand alone unit ,which can perform functions on its own without any requirement for additional hardware like i/o ports and external memory.

The heart of the microcontroller is the CPU core. In the past, this has traditionally been based on a 8-bit microprocessor unit. For example Motorola uses a basic 6800 microprocessor core in their 6805/6808 microcontroller devices.

In the recent years, microcontrollers have been developed around specifically designed CPU cores, for example the microchip PIC range of microcontrollers.

5.1.2 MICROCONTROLLER ATmega8:

PIN DIAGRAM:

5.1.2.1 Features:

High-performance, Low-power AtmelAVR 8-bit Microcontroller

Advanced RISC Architecture

130 Powerful Instructions Most Single-clock Cycle Execution

32 8 General Purpose Working Registers

Fully Static Operation

Up to 16MIPS Throughput at 16MHz

On-chip 2-cycle Multiplier

High Endurance Non-volatile Memory segments

8Kbytes of In-System Self-programmable Flash program memory

512Bytes EEPROM

1Kbyte Internal SRAM

Write/Erase Cycles: 10,000 Flash/100,000 EEPROM

Data retention: 20 years at 85C/100 years at 25C(1)

Optional Boot Code Section with Independent Lock Bits

In-System Programming by On-chip Boot Program

Peripheral Features

Two 8-bit Timer/Counters with Separate Prescaler, one Compare Mode

One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture

Mode

Real Time Counter with Separate Oscillator

Three PWM Channels

8-channel ADC in TQFP and QFN/MLF package

Eight Channels 10-bit Accuracy

6-channel ADC in PDIP package

Six Channels 10-bit Accuracy

Byte-oriented Two-wire Serial Interface

Programmable Serial USART

Master/Slave SPI Serial Interface

Programmable Watchdog Timer with Separate On-chip Oscillator

On-chip Analog Comparator

Special Microcontroller Features

Power-on Reset and Programmable Brown-out Detection

Internal Calibrated RC Oscillator

External and Internal Interrupt Sources

Five Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, and

Standby

I/O and Packages

23 Programmable I/O Lines

28-lead PDIP, 32-lead TQFP, and 32-pad QFN/MLF

Operating Voltages

2.7V - 5.5V (ATmega8L)

4.5V - 5.5V (ATmega8)

Speed Grades

0 - 8MHz (ATmega8L)

0 - 16MHz (ATmega8)

5.1.2.2 PIN DESCRIPTIONS:1.VCC Digital supply voltage.

2.GND Ground.

3. XTAL1/XTAL2/TOSC1/TOSC2

Port B (PB7..PB0)

Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active,even if the clock is not running. Depending on the clock selection fuse settings, PB6 can be used as input to the inverting Oscillator amplifier and input to the internal clock operating circuit.Depending on the clock selection fuse settings, PB7 can be used as output from the inverting Oscillator amplifier.If the Internal Calibrated RC Oscillator is used as chip clock source, PB7..6 is used as TOSC2..1input for the Asynchronous Timer/Counter2 if the AS2 bit in ASSR is set.Port C (PC5..PC0)

Port C is an 7-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors.PC6/RESET

If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electrical characteristics of PC6 differ from those of the other pins of Port C.If the RSTDISBL Fuse is unprogrammed, PC6 is used as a Reset input. A low level on this pin for longer than the minimum pulse length will generate a Reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a Reset.

Port D (PD7..PD0)

Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes active,even if the clock is not running.

RESET

Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset.

5.1.2.3 ATmega8(L)

AVCC AVCC is the supply voltage pin for the A/D Converter, Port C (3..0), and ADC (7..6). It should be externally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter. Note that Port C (5..4) use digital supply voltage, VCC.AREF AREF is the analog reference pin for the A/D Converter.

5.1.2.4 ARCHITECTURAL OVER VIEW

5.2 LCD DISPLAY:

Liquid crystal displays (LCDs) have materials which combine the properties of both liquids and crystals. Rather than having a melting point, they have a temperature range within which the molecules are almost as mobile as they would be in a liquid, but are grouped together in an ordered form similar to a crystal.

An LCD consists of two glass panels, with the liquid crystal material sand witched in between them. The inner surface of the glass plates are coated with transparent electrodes which define the character, symbols or patterns to be displayed polymeric layers are present in between the electrodes and the liquid crystal, which makes the liquid crystal molecules to maintain a defined orientation angle.

One each polarisers are pasted outside the two glass panels. These polarisers would rotate the light rays passing through them to a definite angle, in a particular direction

When the LCD is in the off state, light rays are rotated by the two polarisers and the liquid crystal, such that the light rays come out of the LCD without any orientation, and hence the LCD appears transparent.When sufficient voltage is applied to the electrodes, the liquid crystal molecules would be aligned in a specific direction. The light rays passing through the LCD would be rotated by the polarisers, which would result in activating / highlighting the desired characters.

LCD display:

5.2.1 16 x 2 character LCD display:

An LCD is a small low cost display. it is easy to interface with a micro-controller because of an embedded controller (the black blob on the back of the board). This controller is standard across many displays (hd 44780), which means many micro-controllers have libraries that make displaying messages as easy as a single line of code.

LCD

LCD stands for Liquid Crystal Display. LCD is finding wide spread use replacing LEDs (seven segment LEDs or other multi segment LEDs) because of the following reasons:

1. The declining prices of LCDs.

2. The ability to display numbers, characters and graphics. This is in contrast to LEDs, which are limited to numbers and a few characters.

3. Incorporation of a refreshing controller into the LCD, thereby relieving the CPU of the task of refreshing the LCD. In contrast, the LED must be refreshed by the CPU to keep displaying the data.

4. Ease of programming for characters and graphics.

These components are specialized for being used with the microcontrollers, which means that they cannot be activated by standard IC circuits. They are used for writing different messages on a miniature LCD.

LCD Display

A model described here is for its low price and great possibilities most frequently used in practice. It is based on the HD44780 microcontroller (Hitachi) and can display messages in two lines with 16 characters each . It displays all the alphabets, Greek letters, punctuation marks, mathematical symbols etc. In addition, it is possible to display symbols that user makes up on its own. Automatic shifting message on display (shift left and right), appearance of the pointer, backlight etc. are considered as useful characteristics.

PIN FUNCTIONS:

There are pins along one side of the small printed board used for connection to the microcontroller. There are total of 14 pins marked with numbers (16 in case the background light is built in). Their function is described in the table below:

LCD screen:

LCD screen consists of two lines with 16 characters each. Each character consists of 5x7 dot matrix. Contrast on display depends on the power supply voltage and whether messages are displayed in one or two lines. For that reason, variable voltage 0-Vdd is applied on pin marked as Vee. Trimmer potentiometer is usually used for that purpose. Some versions of displays have built in backlight (blue or green diodes). When used during operating, a resistor for current limitation should be used (like with any LE diode).

LCD display panel

LCD BASIC COMMANDS:

All data transferred to LCD through outputs D0-D7 will be interpreted as commands or as data, which depends on logic state on pin RS:

RS = 1 - Bits D0 - D7 are addresses of characters that should be displayed. Built in processor addresses built in map of characters and displays corresponding symbols. Displaying position is determined by DDRAM address. This address is either previously defined or the address of previously transferred character is automatically incremented.RS = 0 - Bits D0 - D7 are commands which determine display mode. List of commands for lcd:

LCD Connection:

Depending on how many lines are used for connection to the microcontroller, there are 8- bit and 4-bit LCD modes. The appropriate mode is determined at the beginning of the process in a phase called initialization. In the first case, the data are transferred through outputs D0-D7 as it has been already explained. In case of 4-bit LED mode, for the sake of saving valuable I/O pins of the microcontroller, there are only 4 higher bits (D4-D7) used for communication, while other may be left unconnected. Consequently, each data is sent to LCD in two steps: four higher bits are sent first (that normally would be sent through lines D4-D7), four lower bits are sent afterwards. With the help of initialization, LCD will correctly connect and interpret each data received. Besides, with regards to the fact that data are rarely read from

LCD (data mainly are transferred from microcontroller to LCD) one more I/O pin may be saved by simple connecting R/W pin to the Ground. Such saving has its price. Even though message displaying will be normally performed, it will not be possible to read from busy flag since it is not possible to read from display.

LCD Initialization:Once the power supply is turned on, LCD is automatically cleared. This process lasts for approximately 15mS. After that, display is ready to operate. The mode of operating is set by default. This means that:

1. Display is cleared

2. Mode

DL = 1 Communication through 8-bit interface

N = 0 Messages are displayed in one line

F = 0 Character font 5 x 8 dots

3. Display/Cursor on/off

D = 0 Display off

U = 0 Cursor off

B = 0 Cursor blink off

5. Character entry

6. ID = 1 Addresses on display are automatically incremented by 1

S = 0 Display shift off

Automatic reset is mainly performed without any problems. Mainly but not always! If for any reason power supply voltage does not reach full value in the course of 10mS, display will start perform completely unpredictably? If voltage supply unit can not meet this condition or if it is needed to provide completely safe operating, the process of initialization by which a new reset enabling display to operate normally must be applied.Algorithm according to the initialization is being performed depends on whether connection to the microcontroller is through 4- or 8-bit interface. All left over to be done after that is to give basic commands and of course- to display messages .

CIRCUIT DIAGRAM

Advantages and disadvantages of LCD

LCD

Pros:

Very compact and light.

Low power consumption.

No geometric distortion.

Little or no flicker depending on backlight technology.

Not affected by screen burn-in.

No high voltage or other hazards present during repair/service.[citation needed] Can be made in almost any size or shape.

No theoretical resolution limit.

Cons:

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.

KEYPAD

INTRODUCTION

This note describes an method of interfacing a matrix keyboard to EZ328 using minimum number of I/O ports. We use a 4x1 matrix keypad as an example. It requires only five I/O ports. (In general, it takes n+1 ports to interface a nxn matrix keyboard). It is a low cost solution. No TTL logic ICs are used. The components mainly used in the interfacing circuitry include only diodes and resistors which can greatly reduce the system cost and size of the product.

HARDWARE

Figure 1 shows a functional block diagram of the keyboard interface. As seen in this diagram, there are two major parts.

Interrupt & interfacing Circuity - generates interrupt to EZ328 when there is a key pressed and provides connection to EZ328s I/O ports

Keyboard matrix - a 4x1 matrix keypad

Interrupt & interfacing Circuit

The interrupt and interfacing circuit includes some diodes, resistors, pull-up resistors and a NPN transistor.The transistor part is designed as an inverter for generating interrupt signal to EZ328 when there is a key pressed. There are two groups of diodes mainly for restricting signal flow in single direction so as to enable this circuitry to identify the pressed key uniquely. One of these two groups of diodes have been wired together to provide a OR function which in turn allows any key pressed on each column of the keypad to signal the transistor part for generating interrupt.

Parallel Ports Interface

This solution demonstrates a simple mechanism to build a keyboard with minimum I/O port used. In this application, we use a 4x4 matrix keypad as an example. It requires only five I/O ports for interfacing. One of them is used for generating the interrupt signal in the beginning and used as an I/O port for key scanning operation afterwards. Detail of the method in scanning and identifying the pressed key will be discussed in the section SCAN KEYOperation. It should also be noted that in this design, EZ328 uses five ports for interfacing but only one of them requires interrupt capability.

SCAN KEY OPERATION

Five ports are used for key scanning function in this system. One of them (PD7) is used as the interrupt pin before a key is pressed. Before the key scanning process starts, all of the I/O ports except the one with interrupt capability is configured as output high. Then, when there is a key pressed, one of the columns on the keypad changes state from low to high. As all the columns on the keypad are wired together to form a OR logic to the base of the NPN transistor, it will generate an active low interrupt signal to EZ328 and initiates the interrupt handler to scan the pressed key.When the key scanning process begins, one of the five I/O ports will be configured to output high while the other ports are configured to input. The states on all ports are then read and compared with the pattern recorded in a predefined lookup table in order to locate which key is pressed. If the key is not found, another port will be configured to output high instead and read the states again. This process is repeated until all ports have been configured once to output high or a key is found.Since the circuitry provides feedback paths, one of the input port will change state from low to high by the output high port and the states obtained can identify uniquely which key is being pressed. An example of the scanning procedure is illustrated as follows:

5.3 transformer

Potential Transformer is designed for monitoring single-phase and three-phase power line voltages in power metering applications. The primary terminals can be connected either in line-to-line or in line-to-neutral configuration. Fused transformer models are designated by a suffix of "F" for one fuse or "FF" for two fuses. A Potential Transformer is a special type of transformer that allows meters to take readings from electrical service connections with higher voltage (potential) than the meter is normally capable of handling without at potential transformer.

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductorsthe transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.

If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP) as follows:

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP. In the vast majority of transformers, the windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception. Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high voltage power transmission, which makes long distance transmission economically practical.

5.4 CURRENT TRANSFORMER:

In electrical engineering, a current transformer (CT) is used for measurement of electric currents. Current transformers, together with voltage transformers (VT) (potential transformers (PT)), are known as instrument transformers. When current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer also isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current transformers are commonly used in metering and protective relays in the electrical power industry.

Like any other transformer, a current transformer has a primary winding, a magnetic core, and a secondary winding. The alternating current flowing in the primary produces a magnetic field in the core, which then induces a current in the secondary winding circuit. A primary objective of current transformer design is to ensure that the primary and secondary circuits are efficiently coupled, so that the secondary current bears an accurate relationship to the primary current.

The most common design of CT consists of a length of wire wrapped many times around a silicon steel ring passed over the circuit being measured. The CT's primary circuit therefore consists of a single 'turn' of conductor, with a secondary of many hundreds of turns. The primary winding may be a permanent part of the current transformer, with a heavy copper bar to carry current through the magnetic core. Window-type current transformers are also common, which can have circuit cables run through the middle of an opening in the core to provide a single-turn primary winding.

Current transformers are used extensively for measuring current and monitoring the operation of the power grid. Along with voltage leads, revenue-grade CTs drive the electrical utility's watt-hour meter on virtually every building with three-phase service and single-phase services greater than 200 amp.

The CT is typically described by its current ratio from primary to secondary. Often, multiple CTs are installed as a "stack" for various uses. For example, protection devices and revenue metering may use separate CTs to provide isolation between metering and protection circuits, and allows current transformers with different characteristics (accuracy, overload performance) to be used for the different purpose5.5 SIGNAL CONDITIONING UNIT:

The signal conditioning unit accepts input signals from the analog sensors and gives a conditioned output of 0-5V DC corresponding to the entire range of each parameter. This unit also accepts the digital sensor inputs and gives outputs in 10 bit binary with a positive logic level of +5V. The calibration voltages* (0, 2.5 and 5V) and the health bits are also generated in this unit.

Microcontrollers are widely used for control in power electronics. They provide real time control by processing analog signals obtained from the system. A suitable isolation interface needs to be designed for interaction between the control circuit and high voltage hardware. A signal conditioning unit which provides necessary interface between a high power grid inverter and a low voltage controller unit.

5.6 AMPLIFIER:Generally, an amplifier is any device that will convert a signal with a small amount of energy into a similar signal with a larger amount of energy. In popular use, the term today usually refers to an electronic amplifier, often as in audio applications. The relationship of the input to the output of an amplifier usually expressed as a function of the input frequency is called the transfer function of the amplifier, and the magnitude of the transfer function is termed the gain.

General characteristics of amplifiers

Most amplifiers can be characterized by a number of parameters.

Gain

The gain is the ratio of output power to input power, and is usually measured in decibels . (When measured in decibels it is logarithmically related to the power ratio: G(dB)=10log(Pout/Pin)).

Output dynamic range

Output dynamic range is the range, usually given in dB, between the smallest and largest useful output levels. Since the lowest useful level is limited by output noise, this is quoted as the amplifier dynamic range.

Bandwidth and rise time

The bandwidth (BW) of an amplifier is usually defined as the difference between the lower and upper half power points. This is therefore also known as the -3 dB BW. Bandwidths for other response tolerances are sometimes quoted (-1 dB, -6 dB etc.).

A full-range audio amplifier will be essentially flat between twenty hertz to about twenty kilohertz (the range of normal human hearing.) In minimalist amplifier design, the amp's usable frequency response needs to extend considerably beyond this (one or more octaves either side) and typically a good minimalist amplifier will have -3 dB points < 10 and > 65 kHz. Professional touring amplifiers often have input and/or output filtering to sharply limit frequency response beyond 20-20 kHz; too much of the amplifier's potential output power would otherwise be wasted on infrasonic and ultrasonic frequencies, and the danger of AM radio interference would increase. Modern switching amplifiers need steep low pass filtering at the output to get rid of high frequency switching noise and harmonics.The rise time of an amplifier is the time taken for the output to change from 10% to 90% of its final level when driven by a step input.Many amplifiers are ultimately slew rate limited (typically by the impedance of a drive current having to overcome capacitive effects at some point in the circuit), which may limit the full power bandwidth to frequencies well below the amplifiers frequency response when dealing with small signals.For a Gaussian response system (or a simple RC roll off), the rise time is approximated by:Tr * BW = 0.35, where Tr is in seconds and BW is in Hz. Settling time and aberrations

Time taken for output to settle to within a certain percentage of the final value (say 0.1%). This is usually specified for oscilloscope vertical amplifiers and high accuracy measurement systems.

Slew rate

Slew rate is the maximum rate of change of output variable, usually quoted in volts per second (or microsecond).

Noise

This is a measure of how much noise is introduced in the amplification process. Noise is an undesirable but inevitable product of the electronic devices and components. It is measured in either decibels or the peak output voltage produced by the amplifier when no signal is applied.

Efficiency

Efficiency is a measure of how much of the input power is usefully applied to the amplifier's output. Class A amplifiers are very inefficient, in the range of 1020% with a max efficiency of 25%. Class B amplifiers have a very high efficiency but are impractical because of high levels of distortion (See: Crossover distortion). In practical design, the result of a tradeoff is the class AB design. Modern Class AB amps are commonly between 3555% efficient with a theoretical maximum of 78.5%. Commercially available Class D switching amplifiers have reported efficiencies as high as 97%. The efficiency of the amplifier limits the amount of total power output that is usefully available. Note that more efficient amplifiers run much cooler, and often do not need any cooling fans even in multi-kilowatt designs.

5.7 driver circuit:

In electronics, a driver is an electrical circuit or other electronic component used to control another circuit or other component, such as a high-power transistor. The term is used, for example, for a specialized computer chip that controls the high-power transistors in AC-to-DC voltage converters. An amplifier can also be considered the driver for loudspeakers, or a constant voltage circuit that keeps an attached component operating within a broad range of input voltages.

The following circuit will allow you to drive a 12V relay using logic voltage (an input of 4V or greater will trip the relay). The circuit has its own 12V power supply making it self contained but the power supply portion can be left out if an external supply will be used. The circuit shows an output from the power supply that can be used to power other devices but it should be noted that the supply is unregulated and not particulary powerful with the parts stated. The 12V DC output is suitable for powering a few LEDs or low voltage lights but should not be used to power other electronic boards or motors.

5.8 relay: A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism, but other operating principles are also used. Relays find applications where it is necessary to control a circuit by a low-power signal, or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and re-transmitting it to another. Relays found extensive use in telephone exchanges and early computers to perform logical operations. A type of relay that can handle the high power required to directly drive an electric motor is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device triggered by light to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protection relays".

Basic design and operation

Small relay as used in electronics

A simple electromagnetic relay, such as the one taken from a car in the first picture, is an adaptation of an electromagnet. It consists of a coil of wire surrounding a soft iron core, an iron yoke, which provides a low reluctance path for magnetic flux, a movable iron armature, and a set, or sets, of contacts; two in the relay pictured. The armature is hinged to the yoke and mechanically linked to a moving contact or contacts. It is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board (PCB) via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil, the resulting magnetic field attracts the armature, and the consequent movement of the movable contact or contacts either makes or breaks a connection with a fixed contact. If the set of contacts was closed when the relay was De-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low voltage application, this is to reduce noise. In a high voltage or high current application, this is to reduce arcing.

5.9 ALARM

An alarm gives an audible or visual warning about a problem or condition.

Alarms include:

burglar alarms, designed to warn of burglaries; this is often a silent alarm: the police or guards are warned without indication to the burglar, which increases the chances of catching him or her.

alarm clocks can produce an alarm at a given time

distributed control manufacturing systems or DCSs, found in nuclear power plants, refineries and chemical facilities also generate alarms to direct the operator's attention to an important event that he or she needs to address.

alarms in an operation and maintenance (O&M) monitoring system, which informs the bad working state of (a particular part of) the system under monitoring.

safety alarms, which go off if a dangerous condition occurs. Common public safety alarms include:

tornado sirens fire alarms

"Multiple-alarm fire", a locally-specific measure of the severity of a fire and the fire-department reaction required.

car alarms community Alarm or auto dialer alarm (medical alarms)

air raid sirens personal alarm tocsins a historical method of raising an alarm

Alarms have the capability of causing a fight-or-flight response in humans; a person under this mindset will panic and either flee the perceived danger or attempt to eliminate it, often ignoring rational thought in either case. We can characterise a person in such a state as "alarmed".

With any kind of alarm, the need exists to balance between on the one hand the danger of false alarms (called "false positives") the signal going off in the absence of a problem and on the other hand failing to signal an actual problem (called a "false negative"). False alarms can waste resources expensively and can even be dangerous. For example, false alarms of a fire can waste firefighter manpower, making them unavailable for a real fire, and risk injury to firefighters and others as the fire engines race to the alleged fire's location.

CHAPTER-6APPLICATIONS

1. Industries2. EB office

3. Home applications

CHAPTER 7CONCLUSIONThe progress in science & technology is a non-stop process. New things and new Technology are being invented. As the technology grows day by day, we can imagine about the future in which thing we may occupy every place.The proposed system based on Atmel microcontroller is found to be more compact, user friendly and less complex, which can readily be used in order to perform. Several tedious and repetitive tasks. In this phase we collected existing system of meter reading methods and their disadvantages. We analysed the existing method meter reading and we introduced new meter reading method which is very helpful for electricity board. In proposed system we implementing digital energy meter using wifi, for that we collected all hardware details and software details. In phase 2 we implementing the digital energy meter and wireless data acquation system using WIFI.referenceMILL MAN J and HAWKIES C.C. INTEGRATED

ELECTRONICS MCGRAW HILL, 1972

ROY CHOUDHURY D, SHAIL JAIN, LINEAR INTEGRATED CIRCUIT, New Age International Publishers, New Delhi,2000

THE 8051 MICROCONTROLLER AND EMBEDDED SYSTEM by Mohammad Ali Mazidi.

WEBSITES:

http://www.atmel.com/ http://www.microchip.com/ www.8052.com http://www.beyondlogic.org http://www.ctv.es/pckits/home.html http://www.aimglobal.org/CommandRSRWD7D6D5D4D3D2D1D0Execution TimeClear display00000000011.64mSCursor home000000001x1.64mSEntry mode set00000001I/DS40uSDisplay on/off control0000001DUB40uSCursor/Display Shift000001D/CR/Lxx40uSFunction set00001DLNFxx40uSSet CGRAM address0001CGRAM address40uSSet DDRAM address001DDRAM address40uSRead BUSY flag (BF)01BFDDRAM address-Write to CGRAM or DDRAM10D7D6D5D4D3D2D1D040uSRead from CGRAM or DDRAM11D7D6D5D4D3D2D1D040uS