A New Synchronous Generator Out-of Step Relay Scheme Part I Abbreviated Version

In the abbreviated version of the proposed generator out-of-step relay scheme, the equations solved by the powerplant computer are based on a two-machine system model in which the classical representation is used for each machine (the protected machine, or powerplant, and the interconnected system equivalent machine) and resistance is neglected. Tripping is initiated when the iteratively computed value of the Lyapunov V-function during a system disturbance exceeds the V-function´s maximum value b, on the system stability boundary, computed prior to initiation of the scheme´s disturbed-system high-speed computing mode, from preprogrammed and measured predisturbed system data and from preprogrammed postdisturbed system data. Nondelayed tripping prior to the time system torque angle reaches 180°is permitted provided the angle is favorable for breaker operation. If the angle is not favorable at the time instability is detected, tripping is delayed until the angle becomes favorable.