Design and Implementation of Automatic Phase Changer for the Distribution Network using PIC Micro Controller 16F877A

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Design and Implementation of Automatic Phase Changer for the Distribution Network using PIC Micro Controller 16F877A S.Vithiya1, M.Tharanee2, N.Swappana3, G.Subbulakshmi4 UG Student, Dept. of EEE, K.

1 Design and Implementation of Automatic Phase Changer for the Distribution Network using PIC Micro Controller 16F877A S.Vithiya1, M.Tharanee2, N.Swappana3, G.Subbulakshmi4 UG Student, Dept. of EEE, K.Ramakrishnan College Of Engineering, Trichy, Tamilnadu, India Abstract Most domestic supplies at household & semi-industrial premises are supplied from single phase AC. The no. of single phase customers connected to three phase system increases especially in very large scale electrical distribution system.so any one phase of the three phase system gets overloading. In this paper, we bring a new control technique for the distribution line phase changer & used to enhance the solution of electrical load distribution balancing problem where the overloaded phase is automatically changed to other phase by using a relay with the help of pic microcontroller 16F877A by overcoming the manual operation. II. METHODOLOGY In distributed lines, if any one phase of the three phase system gets overloaded, the domestic load connected to that phase becomes abnormal.it is necessary to provide normal voltage for the domestic loads connected in that phase. For that the phase contacts must be change and this is done manually by the line man of Electricity Board using Jumper rods. Index Terms Current transformer, Domestic load, Micro controller, Phase changing, Switching Devices. I. INTRODUCTION The invention of electricity and its advancements in the field of electrical engineering has made electrical energy so vast in its applications. A modern house today, cannot be said to be one if it has no use for electricity.this is because most of the items required for making life fit and comfortable in a home functions with electricity. Electrical appliances like water heaters, radios, televisions, fans, water pumps etc. all have absolute need for electricity. The main aim of this project is to exploit the ubiquitous micro controller facilities in bringing about automation of the phase changeover process. One of the most critical needs of embedded system is to reduce power consumption, space and time & this is achieved in this paper. It has been observed over the years that power failure is occuring, there is a time lag between power failure and when the power is restored to normal level. This system is designed to overcome the short comings of the already existing manual phase changeover. Fig.1. A line man operating jumper rods in the Line. Jumper is a tiny metal connector that is used to close or open part of an electric circuit. It is made up of material that conducts electricity and is sheathed in a non-conductive plastic block to prevent accidental circuit shorts. This time lagging manual operation is replaced by this paper. ISSN: Page 1

2 III. SYSTEM DESIGN AND IMPLEMENTATION.alternating current (AC) in its secondary which is proportional to the AC current in its primary. Current transformers, together with voltage transformers (VTs) or potential transformers (PTs), which are designed for measurement, are known as an Instrument transformer. Current transformers are used in electronic equipment and are widely used for metering and protective relays in the electrical power industry. Fig.4. Sensing Unit Fig.2. The Block Diagram for the Proposed System. The System has i. Power Supply Unit ii. Sensing Unit iii. Signal Conditioning Unit iv. PIC 16F877A Microcontroller v. Switching Unit vi. Driver Circuit The functions of these blocks are explained below. A. Power Supply Unit The power supply unit has a step down transformer(t1). T1 that reduces the high input voltage of 240V to as low as 12V output. It also has a bridge rectifies that converts the low A.C to an equivalent D.C output, though still pulsating in nature. A Low pass filter connected immediately after the rectifies helps to reduce the A.C content bringing out a cleaner increased D.C output. There is a light emitting diode (LED) D5, connected in series with a resistor and both in parallel with the output D.C to help indicate the process is working as designed. Fig.3. Power Supply Unit B. Sensing Unit Sensing unit is a unit which senses any parameter of a system.in our system,we used Current transformer as a sensing unit which senses the current on the line. A current transformer (CT) is a transformer that is used to produce an C. Signal Conditioning Unit A signal conditioner is a device that converts one type of electronic signal into another type of signal. Its primary use is to convert a signal that may be difficult to read by conventional instrumentation into a more easily read format. In performing this conversion a number of functions may take place. The process of converting AC to DC:- Alternating current (AC) is the most efficient way to deliver electrical power. However, most electronic devices need direct current (DC) to function. For this reason, AC to DC converters are either a part of devices themselves or as part of their power cords. If you've built a device you wish to power from an AC outlet, you must add an AC to DC converter. Steps:- a. Determine what your AC input voltage.in India, it's 230 to 240 volts at 50 hertz. The standard in other areas may differ. b. Find the voltage and amperage needed to power the components of your electronic device. Check the manufacturer's instructions, if necessary. Too much of either amperage or voltage will destroy the components, while too little will not allow the device to work correctly. Most have a safe range; aim for the center so your input power can vary somewhat. c. Use a transformer to step down the output from high-voltage AC to low-voltage AC. Electrical current enters the primary coil of the transformer Run the low-voltage AC through a rectifier. A rectifier usually consists of 4 diodes arranged in ISSN: Page 2

The output of both sets is a current that climbs from 0 volts to the maximum positive voltage. d. Add a large electrolytic capacitor to smooth out the voltage.

3 a diamond shape -- a type called a bridge rectifier. A diode only allows current to pass in 1 direction; the diamond configuration allow 2 diodes to pass the positive half of the current and the other 2 diodes to pass the negative half. The output of both sets is a current that climbs from 0 volts to the maximum positive voltage. d. Add a large electrolytic capacitor to smooth out the voltage. A capacitor stores an electrical charge for a short time and then releases it slowly. The input from the rectifier resembles a string of humps; the output of the "smoothing capacitor" is a somewhat steady voltage with ripples.for devices that only need a low current, you can create a regulator with a resistor and a zener diode, which is designed to break down when a certain voltage is reached, allowing current to pass through it. The resistor limits the current. e. Pass the output of the smoother through a regulator. This smooths out the ripples and creates a very steady current that will operate your electronic device without damaging it. Regulators are integrated circuits and can either have fixed or variable output voltages. Although regulators include protection against excessive current and heat, yours may still require that you attach a heat sink to keep it from becoming too hot. f. and induces a current in the secondary coil, which has fewer coils, resulting in a lower voltage. Little power is lost in this process because the amperage increases in relation to the decrease in voltage. D. PIC 16F877A Microcontroller PIC 16F877A finds its applications in a huge number of devices. It is used in remote sensors, security and safety devices, home automation and in many industrial instruments. An EEPROM is also featured in it which makes it possible to store some of the information permanently like transmitter codes and receiver frequencies and some other related data. The cost of this controller is low and its handling is also easy. Its flexible and can be used in areas where microcontrollers have never been used before as in coprocessor applications and timer functions etc. There are 40 pins of this microcontroller IC. It consists of two 8 bit and one 16 bit timer. Capture and compare modules, serial ports, parallel ports and five input/output ports are also present in it. Pin Configuration: PIN 1: MCLR The first pin is the master clear pin of this IC. It resets the microcontroller and is active low, meaning that it should constantly be given a voltage of 5V and if 0 V are given then the controller is reset. Resetting the controller will bring it back to the first line of the program that has been burned into the IC. PIC16F877A reset. A push button and a resistor is connected to the pin. The pin is already being supplied by constant 5V. When we want to reset the IC we just have to push the button which will bring the MCLR pin to 0 potential thereby resetting the controller. PIN 2: RA0/AN0 PORTA consists of 6 pins, from pin 2 to pin 7, all of these are bidirectional input/output pins. Pin 2 is the first pin of this port. This pin can also be used as an analog pin AN0. It is built in analog to digital converter. PIN 3: RA1/AN1 This can be the analog input 1. PIN 4: RA2/AN2/Vref- It can also act as the analog input2. Or negative analog reference voltage can be given to it. PIN 5: RA3/AN3/Vref+ Fig.5a & 5b. Signal Conditioning Unit It can act as the analog input 3. Or can act as the analog positive reference voltage. PIN 6: RA0/T0CKI ISSN: Page 3

4 To timer0 this pin can act as the clock input pin, the type of output is open drain. PIN 7: RA5/SS/AN4 This can be the analog input 4. There is synchronous serial port in the controller also and this pin can be used as the slave select for that port. PIN 8: RE0/RD/AN5 PORTE starts from pin 8 to pin 10 and this is also a bidirectional input output port. It can be the analog input 5 or for parallel slave port it can act as a read control pin which will be active low. PIN 9: RE1/WR/AN6 It can be the analog input 6. And for the parallel slave port it can act as the write control which will be active low. PIN 10: RE2/CS/A7 It can be the analog input 7, or for the parallel slave port it can act as the control select which will also be active low just like read and write control pins. PIN 11 and 32: VDD These two pins are the positive supply for the input/output and logic pins. Both of them should be connected to 5V. PIN 12 and 31: VSS These pins are the ground reference for input/output and logic pins. They should be connected to 0 potential. PIN 13: OSC1/CLKIN This is the oscillator input or the external clock input pin. PIN 14: OSC2/CLKOUT This is the oscillator output pin. A crystal resonator is connected between pin 13 and 14 to provide external clock to the microcontroller. ¼ of the frequency of OSC1 is outputted by OSC2 in case of RC mode. This indicates the instruction cycle rate. the clock input of timer 1 or the oscillator output of timer 2. PIN 16: RC1/T1OSI/CCP2 It can be the oscillator input of timer 1 or the capture 2 input/compare 2 output/ PWM 2 output. PIN 17: RC2/CCP1 It can be the capture 1 input/ compare 1 output/ PWM 1 output. PIN 18: RC3/SCK/SCL It can be the output for SPI or I2C modes and can be the input/output for synchronous serial clock. PIN 23: RC4/SDI/SDA It can be the SPI data in pin. Or in I2C mode it can be data input/output pin. PIN 24: RC5/SDO It can be the data out of SPI in the SPI mode. PIN 25: RC6/TX/CK It can be the synchronous clock or USART Asynchronous transmit pin. PIN 26: RC7/RX/DT It can be the synchronous data pin or the USART receive pin. PIN 19,20,21,22,27,28,29,30: All of these pins belong to PORTD which is again a bidirectional input and output port. When the microprocessor bus is to be interfaced, it can act as the parallel slave port. PIN 33-40: PORT B All these pins belong to PORTB. Out of which RB0 can be used as the external interrupt pin and RB6 and RB7 can be used as in-circuit debugger pins. crystal interfacing with PIC16F877A PIN 15: RC0/T1OCO/T1CKI PORTC consists of 8 pins. It is also a bidirectional input output port. Of them, pin 15 is the first. It can be Fig.6.Pin Configuration of PIC16F877A Microcontroller ISSN: Page 4

E. Switching Unit A switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another.

5 E. Switching Unit A switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. Also can be used to select and ON or OFF state of a system. In a power system the ON state represents power flow while the OFF state represents the otherwise situation. Switches are commonly used in power electrical circuitry. The various switching systems used in power systems include. a) MANUAL SWITCHING: Where a cut-out (an electrical connector device) is used to approximately interconnect and select down the voltage phases by manually plugging in a removable fused connector from one base to the other depending on the one with power. This conventional approach is usually employed in homes often than in industries. b) MECHANICAL SWITCHING: Mechanical switching involves using some sort of mechanism for closing and opening a part of current flow. A typical example is the gang switch used in isolating supply lines. c) ELECTROMECHANICAL SWITCHING: Electromechanical switching is a form of switching which integrates electrical and suitable mechanism for power flow. In this case, power is supplied to the mechanism using solenoids to activate the switching mechanism. d) AUTOMATIC SWITCHING: Automatic switches are those switches that are activated in response to any change in system characteristics (current or voltage). It usually employs relay for detection of change in system characteristics after which a corresponding switching is activated immediately. e) MICRPROCESSOR CONTROLLED SWITCHING: In the case of microprocessor controlled switching a microprocessor chip is software programmed and stored in its memory unit to b interfaced between the available power source and the connected loads. We are using RELAY as a switching devise in our system.a relay is an electrically operated switch that has two major parts coil unit and the contact unit. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contact positions. Relays have two switching positions the normally closed and the normally open. There is no electrical connection between the coil unit and the contact switching position when energized. The link is only magnetic and mechanical. The operational principle of the relay is basically like that of a switch controlled by electromagnetic force. This magnetic force is generated by flow of current through a coil in the relay. The relay opens or closes a circuit when current through the coil is started or stopped. Fig.7.Switching Circuit F. Driver Circuit In our driver circuit we used two topologies, for controlling the switching operation.they are 1. Relay driver IC ULN Darlington driver circuit Relay driver ULN2803: It is a High voltage, high current Transistor Array IC used especially with Microcontrollers where we need to drive high power loads. Thic IC consists of a eight NPN Darlington connected transistors with common Clamp diodes for switching the loads connected to the output. This IC is widely used to drive high loads such Lamps, relays, motors etc. It is usually rated at 50v/500mA. This article brings out the working of ULN2803 IC and how to use it in a circuit.most of the Chips operates with low level signals such as TTL, CMOS, PMOS, NMOS which operates at the range of (0-5)v and are incapable to drive high power inductive loads. However this chip takes low level input signals (TTL) and use that to switch/turn off the higher voltage loads that is connected to the output side. Fig.8.Relay Driver Circuit Darlington driver circuit: A Darlington driver that comes in an IC 18 pin DIL package. ISSN: Page 5

There are 8 drivers in the IC, each driving up to 500mA.Each driver can produce up to 500mA but if every driver is producing 500mA the IC will get hot - possibly very hot.

every output has a diode connected to it - in reverse bias, shown dotted - with the cathodes all connected together.

6 There are 8 drivers in the IC, each driving up to 500mA.Each driver can produce up to 500mA but if every driver is producing 500mA the IC will get hot - possibly very hot.two or more drivers can be connected directly in parallel to produce more current.they can connect to voltages of up to 50v (30v input).every output has a diode connected to it - in reverse bias, shown dotted - with the cathodes all connected together. This is used for inductive loads, such as motors to protect the driver from high EMF voltages created by the coils in the motor. This can be left unconnected if not required.remember that the output sinks current, and thus it should be connected to the negative connection of any device, with the positive connected to the supply.the internal circuit of each driver is shown right - it contains protection and bias resistors.in our system,relay driver IC( ULN2803 ) is capable of controlling eight relay coils and the remaining one relay is controlled by the darlington driver circuit. Fig.10.Simulation of the system using MATLAB. VI. RESULTS The output of the system using the software MATLAB is shown. Fig.11.Result of the system. Fig.9.Darlington Driver Circuit IV. OPERATION The PT is used to check the availability of voltage on the phase and the CT senses the current on the phases.the current value is used for the comparison.if any one phase of the three phase system gets overloaded, the relay changes the phase automatically according to the command generated by micro controller. V. SIMULATION The simulation of this paper was done using a software called MATLAB. VII. CONCLUSION Design and implementation of autophase selection of single phase for distributed lines minimizes damages lives/equipment since it has its own monitoring system and its switching requires no human contact with a switch, thus eliminating human error and it reduces its changeover timing to the minimum due to its fast response to power outage & its maintain high quality of service through its fast and prompt response. VIII. REFERENCES [1] Arindam Ghosh, Senior Member, IEEE, and Avinash Joshi, A New Approach to Load Balancing and Power Factor Correction inpower Distribution System, IEEE Trans. On Power Delivery, vol, 15, no.1, Jan [2] Kolo, J. G., Design and Construction of an Automatic Power Changeover Switch, Assumption University Journal of Technology, (2007), Vol. 11, No. 2, pp [3] Chukwubuikem, N. M., Ekene, M. S. and Uzedhe, G., A Cost Effective Approach to Implementing Changeover System, Academic Research International, (2012), Vol. 2, No. 2, pp [4] Anon., Low Voltage Automatic Transfer Switch System, (2010). [5] F. I. Radha building Automatic Phase Changer ( Chemical press, India ) ISSN: Page 6

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