Adibi - Amir Kabir Technical University
Aelami - Amir Kabir Technical University
Aghajani - Amir Kabir Technical University
Riahi - Amir Kabir Technical University

The probability of occurrence of faults in power systems is not small and the protection system function is very important and critical. In order to prevent power system failure and damages , the protection system must initiate proper commands to the actuators in proper time. In this paper we have proposed a method to calculate main frequency components of voltage and current during fault time , which is essential for distance protection. The method is based on Linear Prediction which by the use of a DigitalSharp Filter,cuts down the calculation time necessary for computation of main frequency components. Digital sharp filters need enough information about the signal which is being filtered. The sharper the filter,more information is necessary.therefore more delay will be involved in very sharp filtering process . By the use of linear prediction method much of these informations can be Predicted based on the fault model. So the process of filtering will be more faster than the usual ethods. The Algorithm is tested by the EMTP ( Electro Magnetic Transient Program ) Software and resaults has shown expected Precision and speed .