WT-3. Inertia of the drive train as protection against tidal turbine runaway
Consider the folowing situation: 1 MW TT tidal turbine (TT) is running at its rated speed of 11 rpm (868 kNm).
There occurs grid loss, generator torque drops to zero, propeller begins to accelerate. Brake will be applied in 0,1 sec (Case 1) or in 0,2 sec (Case 2).
Question: to what speed would the TT accelerate in Cases 1 and 2 if it had the following drive trains configurations:
- without gear (DD),
- with 1-stage gearbox,
- with 2-stage gearbox,
- with 3-stage gearbox?
For all cases there is used PM machine as the generator.
Note: it is known that inertia of rotor of DD electric machine would be 17