Rated MVA -R R ß ß Z MVA MVA = kV 2 /Z (Rc/Rv) angle ß

This study proposes an IEC 61850 based protection scheme to maintain the generator synchronous operation and prevent its tripping by the pole slipping protection (Relay 78) during system disturbances while the transmission line distance protection (R TL) is blocked from operation. The scheme has been studied during common system disturbances, namely sudden load applications. This scheme could maintain the synchronous operation of the local generator and enable it to support the system during and after such disturbances; therefore, maintaining the system stability. A real recorded incidence of generator tripping by Relay 78 in the Egyptian grid is investigated and a new scheme to prevent such tripping during system disturbances is introduced. The new scheme takes the advantage of using IEC 61850 communication standard in coordinating the tripping role between Relay 78 and R TL. This scheme can be applied based on the current technologies of protection relays. The scheme is modeled and simulated using MATLAB ® Software and Xelas IEC 61850 simulator. The simulated system is configured according to the typical parameters of the Egyptian national grid 220 kV. Satisfactory results have proved the scheme effectiveness.