Power Line Monitoring & Protection

8/9/2019 Power Line Monitoring & Protection

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POWER LINE MONITORING &PROTECTION


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Contents

Introduction

Linear Power Supply

Rectifiers

Regulators

PIC Microcontroller Interfacing a PIC with a LCD

Relay

Conclusion


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There is a need to monitor the voltage,current & frequency to protect devices fromvariation of these parameters. Our device is

based on PIC16F877A microcontroller & itmonitors voltage, frequency & current & ifthese parameters go below or above theset limit a relay is turned ON which can be

used to cut the power till the parametersreturn back to normal

Introduction


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Block Diagram


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Linear Power Supply:

An AC powered linear power supplyusually uses a transformer to convertthe voltage from the wall outlet(mains) to a different, usually a lowervoltage.

To produce DC, a rectifier is used. A

capacitor is used to smooth thepulsating current from the rectifier.


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Rectifiers

A rectifier is an electrical device thatconverts alternating current (AC) todirect current (DC), a process knownas rectification. Rectifiers have manyuses including as components ofpower supplies and as detectors of

radio signals


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Regulators:

Regulator (automatic control) is adevice which has the function ofmaintaining a designatedcharacteristic. A voltage regulator isan electrical regulator designed toautomatically maintain a constant

voltage level.


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PIC Microcontroller

PIC16F877A is a small piece of semiconductorintegrated circuits. The package type of thisintegrated circuits is DIP package

Additional components that you need to make this ICwork are just a 5V power supply adapter, a 20MHzcrystal oscillator and 2 units of 22pF capacitors.


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Core Architecture:

The PIC architecture is distinctively minimalist. Itis characterized by the following features:

Separate code and data spaces (Harvardarchitecture)

A small number of fixed length instructions Most instructions are single cycle execution A single accumulator (W), the use of which (as

source operand) is implied (i.e. is not encodedin the opcode)


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Core Architecture:

All RAM locations function as registers as both sourceand/or destination of math and other functions.

A hardware stack for storing return addresses

A fairly small amount of addressable data space

(typically 256 bytes), extended through banking Data space mapped CPU, port, and peripheral

registers

The program counter is also mapped into the dataspace and writable (this is used to implement indirect

jumps).


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Data Space (RAM):PICs have a set of registers that function as general purposeRAM. Special purpose control registers for on-chip hardwareresources are also mapped into the data space.

Code space:

All PICs feature Harvard architecture, so the code space and thedata space are separate. PIC code space is generallyimplemented as EPROM, ROM, or flash ROM.

Word Size:The word size of PICs can be a source of confusion. All PICshandle (and address) data in 8-bit chunks, so they should becalled 8-bit microcontrollers


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Stacks:

PICs have a hardware call stack,which is used to save returnaddresses. The hardware stack is notsoftware accessible on earlierdevices, but this changed with the 18series devices.


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Instruction Set

The instruction set includesinstructions to perform a variety ofoperations on registers directly, theaccumulator and a literal constant orthe accumulator and a register, aswell as for conditional execution, and

program branching.


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In general, PIC instructions fall into 5 classes:

Operation on W with 8-bit immediate ("literal")operand (movlw)(and lw).

Operation with W and indexed register (addwfreg,w)

( addwfreg,f) Bit operations (set or clear a bit, and test and skip on

set/clear )

Control transfers (goto and call )

Zero Operand Instructions(return from subroutine,

and sleep to enter low-power mode)


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Pin Diagram


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5 sets of input and output ports (total of 33ports)

Analog-digital converter of 10 bits of

resolution and 8 channels of entry Peripheral parallel and serial

communication (USART and MSSP)

CPC Modules

3 Timers (1 to 16 bits and 2 of 8 bits) Watchdog timer


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Keypad:

A KEYPAD is a set of buttons arranged in a block whichusually bear digits and other symbols but not a complete set ofalphabetical letters.


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LCD Display


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Interfacing a PIC with a LCD


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Relay:

A relay is an electrically operated switch. Current flowingthrough the coil of the relay creates a magnetic field whichattracts a lever and changes the switch contacts. The coilcurrent can be on or off so relays have two switch positions andthey are double throw (changeover) switches.

COM = Common, always connect to this, it is the moving part ofthe switch.

NC = Normally Closed, COM is connected to this when the relaycoil is off.

NO = Normally Open, COM is connected to this when the relaycoil is on.


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Choosing a Relay

Physical size and pin arrangement

Coil voltage

Coil resistance


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MP Lab Compiler

MPLAB C Compiler is a cross-compiler thatruns on a PC and produces code that canbe executed by the Microchip PIC18XXXX

family of microcontrollers.

ATMEL ISP:ATMEL Microcontroller can programming

with ISP(In-System Programming) whicheasy to develop the applications withoutinsert/remove microcontroller.


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Conclusion:

Increasing worldwide power demands aredriving an increase in the number of powerlines and power-line substations. As moreand more automated monitoring- and fault-detection systems are required, the trendwill be towards systems with a largenumber of channels. With multiple ADCs oneach board, efficient use of board area and

power dissipation become critical as systemdesigners try to reduce cost whileincreasing performance.


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Power Line Monitoring & Protection

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