Current Transformers

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 amps.

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 devices.

Picture above is the type of current transformer. This current transformer is to measure a current and the output will send to the microcontroller.

Omron Relay for the automatic trip

A relay is an electrically operated switch. Relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), 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. 

A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. A contactor is a very heavy-duty relay used for switching electric motors and lighting loads, although contactors are not generally called relays. Continuous current ratings for common contactors range from 10 amps to several hundred amps. High-current contacts are made with alloys containing silver. The unavoidable arcing causes the contacts to oxidize; however, silver oxide is still a good conductor. Such devices are often used for motor starters. A motor starter is a contactor with overload protection devices attached. The overload sensing devices are a form of heat operated relay where a coil heats a bi-metal strip, or where a solder pot melts, releasing a spring to operate auxiliary contacts. These auxiliary contacts are in series with the coil. If the overload senses excess current in the load, the coil is de-energized. Contactor relays can be extremely loud to operate, making them unfit for use where noise is a chief concern.

This relay is use to give an automatic trip to the circuit breaker by sending the signal from the micro controller circuit.

Miature Circuit Breaker (MCB)

       

       Circuit breakers are electrical switching devices for protecting and controlling the electricity supply to respective electrical circuits. Circuit breakers protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. Electrical systems in residential, commercial and industrial applications usually include a panelboard for receiving electrical power from a utility source. The electrical power is then delivered from the panelboard to designated branch circuits supplying one or more loads.

        Overload protection is provided by a thermal element which, when heated by the increased current, will cause the circuit breaker to trip and interrupt the power. Use of circuit breakers is widespread in modern-day residential, commercial and industrial electric systems, and they constitute an indispensable component of such systems toward providing protection against over-current conditions. Various circuit breaker mechanisms have evolved and have been perfected over time on the basis of application-specific factors such as current capacity, response time, and the type of reset (manual or remote) function desired of the breaker.

           Typically, various types of circuit interrupters are connected to the branch circuits to reduce the risk of injury, damage or fires. Circuit interrupters include, for example, circuit breakers, contactors, motor starters, motor controllers, other load controllers and receptacles having a trip mechanism. In the event an overcurrent condition occurs, electrical contacts within the circuit breaker will open, stopping the flow of electrical current through the circuit breaker to the equipment. Circuit breakers have an operating mechanism and trip means, such as a thermal trip assembly and/or magnetic trip assembly, which are automatically releasable to effect tripping operations and manually resettable following tripping operations.

The components inside the circuit breaker:

1. Actuator lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the "on" position. This is sometimes referred to as "free trip" or "positive trip" operation.
2. Actuator mechanism - forces the contacts together or apart.
3. Contacts - Allow current when touching and break the current when moved apart.
4. Terminals
5. Bimetallic strip.
6. Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.
7. Solenoid
8. Arc divider/extinguisher

           

Liquid Crystal Display (LCD)

Liquid Crystal Display (LCD)

This LCD is 2x16 character is use in this project to  display everything such as energy usage in kWh unit and the bill need to pay in RM unit.  This system is already convert from energy usage kWh to a billing in ringgit Malaysia (RM) by refer a tariff domestic from TNB. It also will display the set and preset the amount (RM) for the budget system

Proteus PCB Design

Proteus PCB Design Packages

 

Proteus PCB design combines the ISIS schematic capture and ARES PCB layout programs to provide a powerful, integrated and easy to use suite of tools for professional PCB Design..

All Proteus PCB design products include an integrated shape based auto router and a basic SPICE simulation capability as standard. More advanced routing modes are included in Proteus PCB Design Level 2 and higher whilst simulation capabilities can be enhanced by purchasing the Advanced Simulation option and/or micro-controller simulation capabilities.

Proteus PCB design is used to create a circuit of the microcontroller or project and interfacing with hi tech c compiler in MPLAB for the c code

Create PIC16F series project and program the PIC using MPLAB IDE

MPLAB IDE v8

The current version of MPLAB IDE is version 8.63. It is a 32-bit application on Microsoft Windows and includes several free software components for application development, hardware emulationand debugging. MPLAB IDE also serves as a single, unified graphical user interface for additional Microchip and third-party software and hardware development tools.

Both Assembly and C programming languages can be used with MPLAB IDE v8. Others may be supported through the use of third-party programs.

HI-TECH C

HI-TECH C compiler for PIC16 MCU implements the optimizations of Omniscient Code Generation™ (OCG). Whole program compilation technology to provide denser code and better performance for development on PIC16 MCU.

HI-TECH C compiler is use in MPLAB to create a C programming to the PIC16 series microcontroller unit.

Microcontroller

Introduction:

          This section is the control unit of the whole project. It basically consists of a Micro controller with its associated circuitry like Crystal with capacitors, Reset circuitry, Pull up resistors (if needed) and so on. The Micro controller forms the heart of the project because it controls the devices being interfaced and communicates with the devices according to the program being written.  

   

A Micro controller consists of a powerful CPU tightly coupled with memory RAM, ROM or EPROM), various I / O features such as Serial ports, Parallel Ports, Timer/Counters, Interrupt Controller, Data Acquisition interfaces-Analog to Digital Converter (ADC), Digital to Analog Converter (ADC), everything integrated onto a single Silicon Chip.

          Micro controller has  memory such as RAM, ROM or EPROM and peripherals on a single chip so development of a similar system with a micro controller reduces PCB size and cost of the design.

Micro controller use in the project.

PIC16f877A

 This devices are available in 40-pin packages is shown as picture below.

PIC16f877a

Device features.

Port Function.

In this project each PORT of pin have it own function.

PORT A = Analog to Digital input.

Measurement of analogue variables such as voltage and current must be converted to digital signals in order to be processed by the microcontroller. This microcontrollers have built in analogue to digital converters (ADC), enabling the analogue signals to be fed directly into the input pins of the microcontroller.

PORT B = It use as keypad interface and interrupt function.

PORT C = additional input/output

PORT D =  Use as interfacing LCD