Hazards of wind turbine generator reverse reversal

Can uncontrolled torque reversals affect a wind turbine drive system?

Uncontrolled torque reversals on a wind turbine can damage the drive system beyond the gearbox. The dynamics of a wind turbine and the consequences of these reversals are significant.

How does a generator reversal work?

As the blades pitch, the system sees rapid deceleration of the rotor, continuing through the gearbox to decelerate the generator as well. As seen in Figure 1, the red torque trace shows that torsional reversals can be as high as 75 percent of rated torque (in the negative direction).

What causes reverse power flow in a generator?

As discussed earlier, one cause of reverse power flow in a generator is failure of prime mover. Now failure of prime mover may be because of failure of Governor or failure of Governor Valve or maloperation of Boiler Pressure Control System. Another cause of reverse power flow occurs during synchronization of Generator.

What are the consequences of generator motoring?

The consequences of generator motoring and the level of power drawn from the power system will be dependent on the type of prime mover as under this condition prime mover acts as a load for synchronous Motor. For steam turbines, the motoring power is around 0.5-3 % of rated power of Generator.

Can torsional tripping damage a generator?

These torsional and impact loads can cause potentially significant damage to the surfaces of all the bearings, from main shaft to gearbox and even in the generator. It is not just stopping or tripping modes that can cause these events. Field measurements have captured events that were never recorded by SCADA systems.

What happens if a generator / alternator fails?

If the turbine i.e. prime mover fails the Generator / Alternator connected to the system will continue to operate as synchronous Motor drawing active power from the system. This reversal of power flow due to loss of prime mover can be detected by reverse power relay.