WTT Troubleshooting and Maintenance 3 ā Questions and Answers
Question 1: A wind turbine trips on an overspeed fault during a storm. After the storm passes, what must be verified before restarting?
- Only confirm wind speed has dropped below cut-in speed
- Inspect rotor blades, pitch system, and brake for damage before clearing the fault (Correct answer)
- Reset the fault remotely and allow automatic restart
- Replace the overspeed sensor as a precaution
Correct answer: Inspect rotor blades, pitch system, and brake for damage before clearing the fault
An overspeed event can stress or damage pitch systems, blades, and brakes, so a physical inspection is required before returning the turbine to service.
Question 2: Which of the following correctly describes the function of the yaw brake in a wind turbine?
- It stops the rotor during emergency shutdowns
- It holds the nacelle in position against wind-induced yaw loads when not yawing (Correct answer)
- It limits the pitch angle of the blades during high wind
- It controls the speed of the yaw motor during active yaw
Correct answer: It holds the nacelle in position against wind-induced yaw loads when not yawing
The yaw brake clamps onto the yaw ring to prevent unwanted nacelle rotation when the yaw system is not actively repositioning the turbine.
Question 3: A technician measures insulation resistance on a generator stator winding and gets 50 MĪ© at 1000 V. How should this result be interpreted?
- Excellent insulation ā no action needed
- Acceptable but trending should be monitored (Correct answer)
- Marginal ā schedule rewinding within 30 days
- Critically low ā take the generator offline immediately
Correct answer: Acceptable but trending should be monitored
50 MĪ© is generally acceptable for a wind turbine generator but falls in a range where trending over successive tests is important to detect deterioration.
Question 4: Which maintenance task is specifically designed to prevent fretting corrosion on blade root bolts?
- Applying anti-seize compound and re-torquing bolts to specification (Correct answer)
- Painting the bolt threads with epoxy coating
- Replacing steel bolts with stainless steel fasteners
- Installing rubber gaskets between blade root and hub flange
Correct answer: Applying anti-seize compound and re-torquing bolts to specification
Anti-seize compound reduces micro-motion between mating surfaces, and periodic re-torquing restores clamping force lost due to fretting and relaxation.
Question 5: When a pitch battery backup system fails to hold charge, what is the most likely consequence during a grid fault?
- The turbine will yaw out of the wind automatically
- The blades may fail to feather, causing an uncontrolled overspeed (Correct answer)
- The gearbox will disengage to protect the generator
- The turbine will reduce to minimum power output
Correct answer: The blades may fail to feather, causing an uncontrolled overspeed
Without functional pitch battery backup, the pitch system cannot feather the blades during a power outage or grid fault, risking an overspeed condition.
Question 6: A technician hears a high-pitched metallic squeal from the gearbox during operation. This sound is most consistent with:
- Oil starvation causing dry metal-to-metal gear contact (Correct answer)
- Cavitation in the lubrication pump
- Loose bolts on the gearbox mounting frame
- Bearing cage wear producing cyclic noise
Correct answer: Oil starvation causing dry metal-to-metal gear contact
A high-pitched metallic squeal in a gearbox typically indicates insufficient lubrication, causing direct gear tooth contact and surface distress.
Question 7: What is the correct procedure for testing a wind turbine's emergency stop button?
- Press the button and verify the rotor brakes engage and the turbine reaches a safe stopped state (Correct answer)
- Disconnect the button wiring and verify the safety relay activates
- Test during full power production to simulate worst-case conditions only
- Only test the button during annual inspections as per OEM schedule
Correct answer: Press the button and verify the rotor brakes engage and the turbine reaches a safe stopped state
Functional testing of the emergency stop requires activating it and confirming all expected safety responses occur, including brake engagement and rotor deceleration.
WTT Troubleshooting and Maintenance 3
A wind turbine trips on an overspeed fault during a storm.
After the storm passes, what must be verified before restarting?