Mechanical countermeasures to subsynchronous torsional instability (in turbogenerators)

Abstract

Countermeasures for the subsynchronous resonance problem have been electrical in nature such as series filters, relays, supplementary signals through the excitation system and dynamic filters. A mechanical countermeasure is presented in this paper using a fluid coupling with a flywheel. This paper presents the effect of varying the flywheel inertia and the fluid coupling's characteristics on the mechanical damping. Fluid CouolinqThe fluid coupling is a centrifugal pump and a turbine built together into a single housing. There is no solid connection between the turbine and pump, but rather a liquid, usually oil, is the means to transmit torque from the pump to the turbine. The torque transmission depends on the speed difference between the pump and turbine.For modeling purposes the fluid coupling is considered as a damper between two masses as shown in Figure 1. AS shown in Figure 1 the torque is transmitted from the driving shaft to the driven shaft. Input power is equal to T x w l and output power is equal to Txw2, making the efficiency to be KEYWORDS Subsynchronous resonance, fluid coupling, mechanical coupl ing