31-03-2011, 11:38 AM
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TRANSMISSION LINE MULTIPLE FAULT DETECTION AND INDICATION TO EB
Introduction
Detect faults in remote transmission lines
Immediately transmit any fault information to the Electricity board.
Monitor multiple parameters such as voltage, current and temperature simultaneously
Transfer data through a wireless medium such as Zigbee.
Features
No wires involved
Can detect faults due to over current, under voltage, increased temperature etc.,.
Can operate in any environment in a transmission line.
Can monitor multiple transmission lines sitting in an office.
Block Diagram
VOLTAGE SENSING
Voltage (potential) transformer steps down the voltage in the transmission line.
It is converted into a dc voltage after rectifier and filter.
This rectified dc voltage gives a proportional voltage of the transmission line.
It is fed into the ADC of the microcontroller.
This ADC value gives the voltage present in the transmission line.
CURRENT SENSING
Current transformer senses current taken by the load in a transmission line
The interfacing circuit converts ac current into ac voltage and converts into dc voltage.
The DC voltage is then given to ADC inside microcontroller which calculates the exact current flowing through the line
Depending upon the ADC value the microcontroller finds current in the transmission line.
Temperature Sensing
LM35 is used for temperature sensing
It is a linear centigrade sensor.
The output voltage is given by 10mV/C
Can measure temperatures upto 150’C
Accuracy is within 0.5’C
Integrated sensor in a simple 3pin package.
Block Diagram
Microcontroller
PIC16F877A is the microcontroller used in the project.
The controller has peripheral features like inbuilt ADC, required to get the signals from the sensors.
Maximum clock frequency is 20MHz and hence faster than 8051.
Based on RISC and Harvard architecture and hence even more faster.
Embedded C is used for programming the microcontroller.
Voltage Conversion
Is required because of the mismatch in the operating voltages for Xbee and microcontroller.
Microcontroller operates at 5V and Xbee operates at 3.3V.
Hence direct communication between the two is not possible.
Voltage conversion reduces the voltage from 5V to 3.3V when microcontroller is transmitting.
It increases the voltage from 3.3V to 5V when the Xbee is transmitting.
It is also used in the control room module for the same purpose.
PC Application
A PC is used to monitor the contactor status and the load status.
On the PC a visual basic program will be used.
VB is used because it offers a easy to use and program graphical interface.
The PC displays all the values and also indicates to the user if there is any fault or not.
Hardware Components
PIC 16F877A microcontroller
Sensors
Zigbee transceiver
Max232 for PC interface
PC
Software Tools
MP Lab IDE for PIC programming
Orcad 16 for schematic design
Eagle layout Editor for PCB design
Visual Basic for PC programming in EB office