Algorithms and hardware design of modern numeric overcurrent and distance relays

There has been a significant change in design of protective relays over the past years, due to the advancement in microprocessor and signal processing technology. Due to the advancements in digital technology and decrease in digital hardware prices numeric relays are now available and being used for power system protection. This paper describes fundamental design for a numeric relay and presents algorithms to be used for different protection schemes i.e. overcurrent protection, distance protection, differential protection.