Implementation of Microcontroller Based Distance Relay

In this project microcontroller 8051 was used for comparisons between set Impedance and calculated Impedance for based distance relay of the protection of transmission line, based on that trip signal is send to circuit breaker. The Hardware consisted of main CT and VT, auxiliary VT and CT ,BLF ,sample and hold(S/H) circuit ,multiplexer ,ADC and microcontroller 8051.In which the main CT and VT step down the current and voltage respectably passed to auxiliary CT and VT for protecting the remaining components and convert the current into voltage in the output of auxiliary CT, then passed it to band limit filter to limit the frequency for sampling hold after sampling and hold circuit the signal is passed to multiplexer then to the ADC for analogue to digital conversion, after the conversion the digital signals is passed to the 8051 microcontroller to processing the signals that is calculating the average, impedance and compare it with the set impedance (store impedance) to generate trip signal when calculate impedance is less than or equal to set impedance. The trip signal is send to circuit breaker for tripping the first zone if condition is no it go to zone second zone and check the condition if yes trip is send to circuit breaker if no it go to third zone if yes trip and jump to initial point if not it go back to initial point. The relay software has been developed and simulated using Proteus software in which signal generator, ADC, microcontroller and LEDs are used for the purpose of checking fault in transmission.