Multifunctional directional transversal difference protection device by microcomputer

This paper describes the first successful power system device with multifunctional directional transversal difference protection in China. It realized some protection action performances which are difficult for conventional relay protection. Especially, eliminating both the voltage dead-zone and increasing action sensitivity and selectability are important improvements over conventional relay protection. By using the advantages of microcomputers, this device has created some new functions which are impossible for conventional protection, and has progressed toward the direction of multifunctionality and automation. It has been successfully in field operation in a 66 kV substation in Liaoning Province since May of 1992.<>