Development of instantaneous transient torque protection against torque amplification for turbine generators in a series-compensated power system

Abstract The torque amplification (TA) in turbine generators connected to a series-compensated network could cause excessive fatigue loss-of-life (FLoL) or even a sudden shaft failure, and thus poses a major threat to the shaft safety. This paper develops an instantaneous transient torque protection (ITTP) scheme to ensure shaft safety. It adopts the shaft speed to estimate transient torque in real-time and then judges whether to trip the generator by comparing the estimated transient torque with the pre-set tripping thresholds. As the key parameters of the proposed protection scheme, the tripping thresholds are delicately tuned based on the most severe circumstance, ensuring the inflicted FLoL less than the tolerable value and avoiding mal-operation under all possible circumstances. A prototype ITTP is developed and its performance is thoroughly verified through real-time digital simulator (RTDS)-based hardware-in-the-loop (HIL) tests on a practical series-compensated power system. The results under a variety of operating conditions and disturbances have well demonstrated the effectiveness of the developed ITTP in estimating transient torque and protecting the generator from damage caused by impulsive transient torque.