Faults in power systems are to be cleared rapidly with relays having high speed of operation, selectivity, reliability and security of the trip decision that assumes more important.Power system under faulted state contains decaying Dc offset, harmonics, characteristic frequency components and noise along with fundamental frequency component which is given as input for relay to generate trip decision. Precision of fundamental frequency components extraction from faulted signals is greatly affected with the presence of above said unwanted frequency components. Digital filtering algorithms must have to extract desired parameters within less computational time and they are of exact values. Some digital filtering algorithms are presented in this book along with their performance analysis when tested on different test systems. Results shown the effective working of the proposed algorithms.