Design and implementation of quadrilateral relay using microcontroller atmega328 for the protection of transmission line equivalent model

Abstract

Protection of transmission line equivalent model has been done by using microcontroller based quadrilateral relay. This relaying protection scheme protects the transmission line equivalent model from single line to ground (L-G) fault. The overall process is monitored by ARDUINO UNO board including ATmega328 microcontroller. The main reason for using the quadrilateral relay is that it has the valuable property of possessing the least tendency for mal-operation due to heavy power swings, arc resistance, fault resistance and overloads. Its characteristics can be designed to just enclose the fault area of the line to be protected. The determination of quadrilateral characteristics has been completed through software. The data acquisition system (DAS) includes instrument transducers (CTs and VTs), i to v converter, filters, phase shifter, zero crossing detectors, bridge rectifiers and sample and hold (S/H) circuits. The ATmega328 senses the voltage and current values to compute the impedance of the equivalent line model and then compares the measured value with the prespecified value. If the measured value exceeds the prespecified value the microcontroller issues a trip signal to the circuit breaker and hence isolates the unhealthy portion of the transmission line equivalent model from the rest of the line. A single phase series R-L equivalent model of the transmission line has been achieved by using four modules of inductance and resistance connected in series. The capacitance has been neglected for the test purpose. Each module represents 50 kms of transmission line and hence a total of 200 kms, where the first zone represents 100 kms, second zone extends upto 150 kms and finally the third zone represents 200 kms. By closing the switches at different points of the transmission line faults have been created at these points, with bus voltage maintained at 220 volts for the model. Current and potential transformers have been used to step down the level of fault signal to the electronic level. Input signals of current and voltage have been simulated using specially designed phase shifter, zero crossing detector and sample and hold circuits. The software developed for the determination of the characteristics has been stored in the memory of the microcontroller system and executed. The whole circuitry has been designed and developed on the hardware. The DAS has also been simulated using MULTISIM software.