Analysis of mechanical stresses developed on T-G shaft during faults

The instability of an interconnected power system means a condition denoting loss of synchronism or falling out of phase. Stability considerations have been recognized as an essential part of power system planning for a long time. With interconnected systems continually growing in size and extending over vast geographical regions, it is becoming increasingly more difficult to maintain synchronism between various parts of power system. It is found that due to transient disturbance generator speeds up causing motor angle to increase resulting in the development of varying torque on the rotor of generator. This varying torque develops the varying stresses on the motor shaft which when crosses the endurance limit i.e 45 times 10⁷ N/m² leads to damage of the shaft. In this paper a strategy is presented which seeks the coordination of generator drooping, fast valving and resynchronising the dropped generator by 120deg phase rotation. The implementation of this strategy will enable more effective use of generator dropping without load shedding which is normally associated with generator dropping.