NFPA Certified Wind Turbine Technician-I (WTT-I) — Questions and Answers

Question 1: What is the purpose of the DC chopper (braking resistor circuit) in a wind turbine's power converter?

To limit inrush current when the converter first energizes
To dissipate excess DC bus energy during grid faults or overspeed events (Correct answer)
To provide reactive power compensation during low-wind periods
To smooth output current ripple on the grid side

Correct answer: To dissipate excess DC bus energy during grid faults or overspeed events

The DC chopper switches a resistor across the DC bus to burn off excess energy when the bus voltage rises above a threshold, protecting capacitors and IGBTs.

Question 2: Which instrument is best suited for locating a high-resistance connection in a wind turbine's 690 V bus system?

Megohmmeter (Megger)
Clamp-on ammeter
Phase sequence tester
Infrared thermographic camera (Correct answer)

Correct answer: Infrared thermographic camera

Infrared thermography detects heat signatures from high-resistance connections under load without requiring circuit de-energization.

Question 3: What is the role of the teeter mechanism found on some two-bladed rotors?

Controls yaw rate during high winds
Adjusts blade pitch independently on each blade
Allows the rotor hub to rock slightly to reduce cyclic fatigue loads (Correct answer)
Couples two blades for synchronous pitch movement

Correct answer: Allows the rotor hub to rock slightly to reduce cyclic fatigue loads

A teetering hub permits small rocking motions of the rotor to absorb asymmetric aerodynamic loads, significantly reducing tower and drivetrain fatigue.

Question 4: Before entering a wind turbine blade for an internal inspection, which hazard must be assessed due to the blade's enclosed composite structure?

Thermal runaway from embedded heating elements
Oxygen-deficient atmosphere from resin off-gassing (Correct answer)
Radio frequency interference from nearby turbines
Electrostatic discharge from blade rotation

Correct answer: Oxygen-deficient atmosphere from resin off-gassing

Enclosed blade interiors can accumulate toxic fumes or become oxygen-deficient from curing resin off-gassing, requiring atmospheric testing before entry.

Question 5: What is the consequence of over-greasing a wind turbine pitch bearing?

Reduced corrosion protection in the bearing raceway
Grease churning, heat buildup, seal damage, and potential bearing failure due to excess pressure (Correct answer)
No consequence — excess grease is expelled harmlessly
Improved lubrication film and extended bearing life

Correct answer: Grease churning, heat buildup, seal damage, and potential bearing failure due to excess pressure

Over-greasing causes excess grease to churn, generating heat that degrades the grease and can damage seals or cause abnormal bearing loads.

Question 6: What documentation practice is considered essential in Hydraulic & Lubrication Systems within the Wind Turbine Technician field?

Recording actions, observations, and outcomes in real-time or as close to the event as possible (Correct answer)
Completing all documentation at the end of the workday
Using shorthand notes that can be expanded later if needed
Only documenting unusual events or complications

Correct answer: Recording actions, observations, and outcomes in real-time or as close to the event as possible

Real-time or near-real-time documentation in Hydraulic & Lubrication Systems ensures accuracy, provides a contemporaneous record, and is considered the gold standard for professional accountability and legal defensibility.

Question 7: What is the role of the pitch control system in wind turbines?

To adjust the speed of the generator.
To monitor the electrical grid.
To regulate the temperature of the generator.
To change the angle of the blades to control rotor speed. (Correct answer)

Correct answer: To change the angle of the blades to control rotor speed.

The pitch control system is responsible for adjusting the angle of the wind turbine blades relative to the wind. This allows the turbine to optimize energy capture in varying wind speeds and acts as a critical safety mechanism to slow down or stop the rotor during high winds or emergencies. By changing the blade angle, it directly controls the rotor's speed and power output.

Question 8: During an inspection, a technician finds whitish streaks radiating from a drilled hole in a blade shell. This pattern most likely indicates:

Impact damage from foreign object debris
Moisture staining from condensation inside the blade
Residue from improper mold release agent application
Stress cracking (crazing) propagating from a drilled stress concentrator (Correct answer)

Correct answer: Stress cracking (crazing) propagating from a drilled stress concentrator

Radial whitish cracks or crazing emanating from a hole indicate that stress concentration at the drilled edge has initiated matrix cracking in the surrounding laminate.

Question 9: What is the minimum safe horizontal distance a technician must maintain from the base of a tower during a drop-zone hazard assessment?

1 times the tower height (Correct answer)
2 times the tower height
1.5 times the tower height
0.5 times the tower height

Correct answer: 1 times the tower height

A horizontal exclusion zone of at least 1× the tower height is the standard minimum to protect ground personnel from falling objects.

Question 10: How does risk management apply to daily practice in Blade Inspection & Maintenance for Wind Turbine Technician professionals?

Through proactive identification of potential hazards and implementation of preventive measures (Correct answer)
By avoiding high-risk situations entirely
Through annual safety audits exclusively
Only through responding to incidents after they occur

Correct answer: Through proactive identification of potential hazards and implementation of preventive measures

Effective risk management in Blade Inspection & Maintenance requires proactive hazard identification and preventive measures, not just reactive responses. This approach reduces incidents, improves outcomes, and protects both professionals and clients.

Question 11: A technician notices a turbine's SCADA shows frequent 'grid voltage fluctuation' faults. Which component should be investigated first?

The main circuit breaker and grid monitoring relay (Correct answer)
The yaw position sensor
The pitch controller calibration
The nacelle anemometer

Correct answer: The main circuit breaker and grid monitoring relay

Grid voltage fluctuation faults point to the grid monitoring relay and main breaker, which monitor voltage levels and disconnect the turbine when grid quality falls outside acceptable limits.

Question 12: During a gearbox oil change, a technician finds the oil appears milky white. What is the most probable cause?

Gear additive package breakdown from overheating
Water contamination causing an oil-water emulsion (Correct answer)
Excessive foam from overfilling the gearbox
Mixing of two incompatible oil grades

Correct answer: Water contamination causing an oil-water emulsion

Milky white oil is the classic visual sign of water emulsification, typically caused by condensation, rain ingress, or a failed cooling-circuit seal.

Question 13: What is the typical frequency of the AC voltage produced by a wind turbine generator before conversion for US grid connection?

50 Hz, to match European standards
60 Hz, matching the grid at all times
120 Hz, due to the high pole count
Variable frequency, depending on rotor speed (Correct answer)

Correct answer: Variable frequency, depending on rotor speed

Variable-speed wind turbines produce variable-frequency AC that is converted to DC and then inverted to fixed 60 Hz for grid connection.

Question 14: The term 'void content' in a blade laminate repair refers to:

Missing fiber plies in the original blade layup schedule
The percentage of the blade span that lacks structural reinforcement
The volume fraction of trapped air bubbles within the cured resin matrix (Correct answer)
The empty space inside the hollow blade cavity

Correct answer: The volume fraction of trapped air bubbles within the cured resin matrix

Void content is the percentage of air pockets entrapped within the cured composite, which reduces mechanical properties — acceptable repairs typically specify less than 2% void content.

Question 15: Which type of grounding system is most commonly used in wind turbine nacelle electrical panels in the US?

Solidly grounded wye (Correct answer)
Corner-grounded delta
Ungrounded delta
High-resistance grounded

Correct answer: Solidly grounded wye

Solidly grounded wye systems are standard in US wind turbine panels because they limit fault voltages and are required by NEC for most applications.

Question 16: What is the minimum safe distance a ground crew member should maintain from a wind turbine during rotor rotation when ice shedding conditions exist?

10 meters
50 meters
Rotor diameter + hub height (Correct answer)
1.5× rotor diameter

Correct answer: Rotor diameter + hub height

Ice throw distance calculations typically use rotor diameter plus hub height as the minimum exclusion zone during icing conditions.

Question 17: In Hydraulic & Lubrication Systems, what is the FIRST step a WTT professional should take when encountering a new case or situation?

Document the situation and wait for further instructions
Consult with a supervisor before taking any action
Implement an immediate solution based on past experience
Conduct a comprehensive assessment and gather all relevant information (Correct answer)

Correct answer: Conduct a comprehensive assessment and gather all relevant information

In Hydraulic & Lubrication Systems, a thorough initial assessment ensures all relevant factors are identified before deciding on an appropriate course of action. This systematic approach is fundamental to Wind Turbine Technician practice.

Question 18: When using a self-retracting lifeline (SRL) for horizontal movement inside a nacelle, the SRL must be anchored:

Anywhere on the nacelle frame that feels secure
To the nearest available structural bolt
At or above the dorsal D-ring level on a rated anchor point (Correct answer)
At foot level for best arrest geometry

Correct answer: At or above the dorsal D-ring level on a rated anchor point

SRL anchors must be at or above dorsal D-ring height on a rated structural anchor point to minimize fall distance and arrest forces.

Question 19: Which type of coupling is most commonly used between the gearbox output shaft and the generator input shaft in a wind turbine?

Jaw coupling
Chain coupling
Flexible disc coupling (Correct answer)
Rigid flange coupling

Correct answer: Flexible disc coupling

Flexible disc couplings accommodate misalignment and dampen torsional vibrations between the gearbox and generator shafts.

Question 20: What is 'micropitting' in the context of wind turbine gearbox gears, and what operating condition promotes it?

Fine surface cracks and material loss on gear tooth flanks caused by inadequate lubricant film thickness at low speed or partial load (Correct answer)
Macro-spalling of the gear tooth case hardened layer during high-torque startup events
Large fatigue cracks at the gear tooth root caused by high bending stress during storm loading
Abrasive wear of gear tooth tips caused by contaminated lubrication

Correct answer: Fine surface cracks and material loss on gear tooth flanks caused by inadequate lubricant film thickness at low speed or partial load

Micropitting is a surface fatigue phenomenon where thin EHD film at partial load or low speed allows metal-to-metal contact, producing a frosted grey appearance on tooth flanks.

Question 21: What should be checked when inspecting the wind turbine’s electrical system?

The generator’s fuel consumption.
Only the inverter connections.
Wiring integrity, inverters, circuit breakers, and grounding. (Correct answer)
The color of the wiring.

Correct answer: Wiring integrity, inverters, circuit breakers, and grounding.

When inspecting a wind turbine's electrical system, it's crucial to check all components involved in power generation and transmission. This includes verifying the integrity of all wiring for damage or loose connections, inspecting inverters for proper operation, checking circuit breakers for trips or faults, and ensuring proper grounding for safety and system stability. A thorough inspection of these elements helps prevent electrical failures and ensures efficient power output.

Question 22: What is the primary purpose of a 'tail rope' during turbine blade lifting operations?

To signal the crane operator
To measure blade weight distribution
To provide ground crew control of blade orientation and prevent uncontrolled rotation (Correct answer)
To attach secondary lifting points

Correct answer: To provide ground crew control of blade orientation and prevent uncontrolled rotation

Tail ropes allow ground personnel to control blade orientation and prevent dangerous uncontrolled spinning during crane lifts.

Question 23: What is the purpose of a wind turbine's transformer located at the base of the tower?

To regulate blade pitch servo pressure
To step up generator voltage to grid transmission voltage (Correct answer)
To convert AC power to DC for battery storage
To filter harmonics from the yaw drive motor

Correct answer: To step up generator voltage to grid transmission voltage

The pad-mount or tower-base transformer steps up the low generator voltage (typically 690 V) to medium-voltage grid level (e.g., 34.5 kV) for efficient transmission.

Question 24: What is the primary function of a crowbar circuit in a wind turbine's power converter?

To protect the DC link capacitors by shorting the rotor circuit during voltage transients (Correct answer)
To synchronize the generator frequency with the grid
To disconnect the generator from the grid during faults
To regulate reactive power output during normal operation

Correct answer: To protect the DC link capacitors by shorting the rotor circuit during voltage transients

A crowbar circuit protects the rotor-side converter by shorting the rotor windings during grid voltage transients, preventing DC link overvoltage.

Question 25: In wind turbine tower design, why are tubular steel towers preferred over lattice (truss) towers for most onshore installations?

Tubular towers can be constructed without welding in the field
Tubular towers eliminate the need for a foundation anchor system
Tubular towers are always lighter and use less steel than lattice designs
Tubular towers are safer to climb, reduce icing hazards, and are more aesthetically accepted (Correct answer)

Correct answer: Tubular towers are safer to climb, reduce icing hazards, and are more aesthetically accepted

Tubular towers enclose the climb path inside the structure for technician safety, minimize ice shedding risks, and are more visually accepted by communities near wind farms.

Question 26: When a conflict arises between standard procedures and a unique situation in Tower Climbing & Rescue Safety, what should a WTT professional prioritize?

The preference of the client or stakeholder
The most cost-effective solution available
Strict adherence to written procedures without exception
Safety and ethical obligations while seeking expert consultation (Correct answer)

Correct answer: Safety and ethical obligations while seeking expert consultation

Safety and ethics always take priority in Tower Climbing & Rescue Safety. When standard procedures don't adequately address a unique situation, consulting with experienced colleagues or supervisors ensures both safety and professional standards are maintained.

Question 27: During PM, a technician checks the cooling system of a liquid-cooled generator and finds coolant level low. What should be done before adding coolant?

Only top off if below the minimum mark by more than 20%
Add coolant immediately and document
Inspect for leaks, identify and repair the source, then refill to specified level (Correct answer)
Drain and refill the entire system

Correct answer: Inspect for leaks, identify and repair the source, then refill to specified level

Low coolant always indicates a potential leak; the source must be identified and repaired before refilling to prevent recurrence and coolant loss.

Question 28: What does a 'pre-task safety assessment' (Job Hazard Analysis) for a tower climb specifically require the technician to document?

Wind speed at sea level and nearest hospital distance
Supervisor approval signature and equipment cost
Turbine serial number and service history only
Identified hazards, control measures, emergency procedures, and PPE required (Correct answer)

Correct answer: Identified hazards, control measures, emergency procedures, and PPE required

A JHA must identify all hazards, the controls to mitigate them, emergency response procedures, and the required PPE before work begins.

Question 29: Which of the following is a key safety measure when working on electrical systems of wind turbines?

Use insulated gloves only.
Confirm the turbine is de-energized and locked out. (Correct answer)
Increase the voltage for better safety.
Check for visible electrical sparks.

Correct answer: Confirm the turbine is de-energized and locked out.

The most critical safety measure when working on electrical systems is to ensure they are completely de-energized and secured using lockout/tagout procedures. This prevents accidental energization, which could lead to severe injury or fatality. All other safety measures, like insulated gloves, are secondary to ensuring the system is truly off.

Question 30: At what water content level (ppm) does water in hydraulic oil typically begin to cause significant bearing damage through hydrogen embrittlement?

Greater than 50,000 ppm
Greater than 500 ppm (Correct answer)
Any detectable water above 0 ppm
Greater than 5,000 ppm

Correct answer: Greater than 500 ppm

Water concentrations above approximately 500 ppm promote hydrogen embrittlement and accelerated fatigue in hardened bearing steel.

Question 31: A technician is required to work inside a confined space within the tower base. Before entry, which document must be completed?

Tool inventory sheet
Standard work order
Electrical isolation certificate only
Permit-Required Confined Space Entry Permit (Correct answer)

Correct answer: Permit-Required Confined Space Entry Permit

A Permit-Required Confined Space Entry Permit must be completed and authorized before any entry into a permit-required confined space.

Question 32: What does the term 'solidity' refer to in the context of wind turbine rotor design?

The density of the blade composite material in kg/m³
The stiffness coefficient of the blade root connection
The percentage of time the rotor operates at rated speed
The ratio of total blade area to the swept rotor area (Correct answer)

Correct answer: The ratio of total blade area to the swept rotor area

Rotor solidity is the fraction of the swept area covered by blade material; low-solidity three-bladed designs are optimal for high-TSR, high-efficiency operation.

Question 33: Which type of blade erosion is caused primarily by repeated impact of airborne particles such as rain, dust, and insects at high tip speeds?

Trailing edge fatigue cracking
Galvanic corrosion
Spar cap delamination
Leading edge erosion (Correct answer)

Correct answer: Leading edge erosion

Leading edge erosion occurs when high-velocity impacts from rain, sand, and insects progressively erode the blade's leading edge coating and laminate.

Question 34: What is the purpose of a transformer in a wind turbine electrical system?

To adjust voltage for grid compatibility. (Correct answer)
To store electrical energy.
To convert mechanical energy into electrical energy.
To regulate wind speed.

Correct answer: To adjust voltage for grid compatibility.

Transformers are vital components in a wind turbine's electrical system, primarily used to adjust voltage levels. They step up the voltage of the electricity generated by the turbine to a higher level suitable for efficient transmission over long distances via the electrical grid. This minimizes power loss during transmission and ensures grid compatibility.

Question 35: When applying an epoxy repair to a blade in the field, the minimum acceptable ambient temperature for most two-part epoxy systems is typically:

65°F (18°C)
35°F (2°C)
0°F (-18°C)
50°F (10°C) (Correct answer)

Correct answer: 50°F (10°C)

Most field-grade epoxy repair systems require a minimum substrate and ambient temperature of approximately 50°F (10°C) to achieve proper cure and adhesion.

Question 36: A wind farm's site safety plan specifies a 'stop work authority' policy. This policy means:

Only the site manager may halt operations
Any worker who observes an unsafe condition has the right and responsibility to stop work (Correct answer)
Work stoppages require a majority crew vote
OSHA must be notified before stopping work

Correct answer: Any worker who observes an unsafe condition has the right and responsibility to stop work

Stop work authority empowers every worker — regardless of rank — to halt operations when they observe an immediate safety threat.

Question 37: Which maintenance task is specifically designed to prevent fretting corrosion on blade root bolts?

Painting the bolt threads with epoxy coating
Replacing steel bolts with stainless steel fasteners
Installing rubber gaskets between blade root and hub flange
Applying anti-seize compound and re-torquing bolts to specification (Correct answer)

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 38: What is the purpose of a kidney loop filtration system on a wind turbine gearbox?

To continuously filter the gearbox oil offline to maintain cleanliness targets (Correct answer)
To add new oil automatically when levels drop
To cool the hydraulic pump only
To circulate oil during transport before installation

Correct answer: To continuously filter the gearbox oil offline to maintain cleanliness targets

A kidney loop is an independent filtration circuit that continuously polishes gearbox oil to achieve and maintain target ISO cleanliness codes.

Question 39: What does 'swept area' refer to in wind turbine specifications?

The circular area traced by the rotating blades (Correct answer)
The floor area of the nacelle service platform
The surface area of the tower exterior
The land area required for turbine installation

Correct answer: The circular area traced by the rotating blades

Swept area is the circular disc traced by blade tips during rotation; it directly determines how much wind energy the turbine can intercept.

Question 40: What is the PRIMARY purpose of continuing education requirements in Blade Inspection & Maintenance for WTT professionals?

Earning additional credentials for career advancement
Fulfilling mandatory regulatory requirements only
Networking with other professionals in the field
Maintaining current knowledge and competency as the field evolves (Correct answer)

Correct answer: Maintaining current knowledge and competency as the field evolves

Continuing education in Blade Inspection & Maintenance ensures professionals maintain current knowledge and skills as standards, technologies, and best practices evolve in the Wind Turbine Technician field.

Question 41: What is the function of a load cell in a crane or rigging lifting operation?

It controls the speed of the crane hoist drum
It measures the actual weight of the suspended load in real time (Correct answer)
It stores electrical power for the crane's control system
It verifies the load's center of gravity before the lift begins

Correct answer: It measures the actual weight of the suspended load in real time

A load cell is a force-measuring instrument placed in line with the rigging that displays the actual dynamic load on the hook during the lift.

Question 42: What condition is indicated when hydraulic fluid appears milky or cloudy?

High concentration of anti-wear additives
Water contamination causing an oil-water emulsion (Correct answer)
Excessive air entrainment only
Correct viscosity blend of two oil grades

Correct answer: Water contamination causing an oil-water emulsion

Milky or cloudy hydraulic fluid is a classic sign of water contamination creating an emulsion that severely degrades lubrication properties.

Question 43: When performing a hydraulic hose replacement on a pitch cylinder, what is the critical final step before returning the system to service?

Paint the hose fittings with matching color
Increase reservoir oil level by 10%
Bleed air from the hydraulic circuit and verify system pressure and leak-free operation (Correct answer)
Recalibrate the wind vane sensor

Correct answer: Bleed air from the hydraulic circuit and verify system pressure and leak-free operation

After any hose replacement, bleeding trapped air and verifying correct pressure and no leaks is mandatory before restoring service.

Question 44: When conducting an oil analysis program, what is the recommended sampling point for the most representative gearbox oil sample?

From the top of the reservoir using a clean tube
From the overflow port only
From the drain plug at the bottom of the sump
From the return line upstream of the filter while the gearbox is at operating temperature (Correct answer)

Correct answer: From the return line upstream of the filter while the gearbox is at operating temperature

Sampling from the return line at operating temperature captures a representative circulating sample with wear particles before they are filtered out.

Question 45: What is the PRIMARY purpose of continuing education requirements in Electrical Systems & Power Generation for WTT professionals?

Fulfilling mandatory regulatory requirements only
Maintaining current knowledge and competency as the field evolves (Correct answer)
Networking with other professionals in the field
Earning additional credentials for career advancement

Correct answer: Maintaining current knowledge and competency as the field evolves

Continuing education in Electrical Systems & Power Generation ensures professionals maintain current knowledge and skills as standards, technologies, and best practices evolve in the Wind Turbine Technician field.

Question 46: What is the recommended recovery position for a victim retrieved after prolonged harness suspension?

Prone (face down) to drain fluids
Seated upright immediately
Semi-recumbent (sitting at 45°) for 30 minutes before lying flat (Correct answer)
Flat supine with legs elevated

Correct answer: Semi-recumbent (sitting at 45°) for 30 minutes before lying flat

Gradually transitioning from seated to supine prevents a sudden rush of pooled blood returning to the heart, which could cause cardiac arrest.

Question 47: A technician notices a faint 'click' sound when tapping along a blade surface with a coin or small hammer. This tap-test result indicates:

Normal cured composite resonance
The blade has adequate resin saturation
A void or delamination beneath the surface (Correct answer)
Blade over-tension due to wind loading

Correct answer: A void or delamination beneath the surface

A hollow or clicking sound during a tap test indicates a subsurface void or delamination where the laminate has separated from adjacent layers or core material.

Question 48: What is the purpose of a 'deadband' setting in a wind turbine PID controller?

To define the range of wind speeds for partial-load operation
To set the minimum rotor RPM before grid connection
To prevent the controller from responding to small, insignificant error signals (Correct answer)
To limit the maximum output power of the generator

Correct answer: To prevent the controller from responding to small, insignificant error signals

A deadband prevents the controller from making unnecessary corrections when the error signal is within an acceptable range, reducing actuator wear.

Question 49: A wind turbine's SCADA system reports a negative power factor reading from the revenue meter at the point of interconnection. What does this most likely indicate?

The turbine is operating in motoring mode, consuming active power from the grid
The CT polarity connections are reversed, causing a sign error in the measurement
The turbine has tripped offline and is reading residual magnetism
The turbine is absorbing reactive power from the grid (lagging PF, consuming VARs) (Correct answer)

Correct answer: The turbine is absorbing reactive power from the grid (lagging PF, consuming VARs)

A negative power factor at the POI typically means the turbine is absorbing reactive power (VARs) from the grid rather than supplying it, often a deliberate control setpoint or a converter control issue.

Question 50: When a tandem (two-crane) lift is required to install a wind turbine tower section, who is responsible for coordinating the movements of both cranes?

A single designated lift director who issues all movement commands (Correct answer)
Each crane operator independently follows hand signals from separate signalers
The project manager from the wind farm owner
The manufacturer's field representative on site

Correct answer: A single designated lift director who issues all movement commands

ASME B30.2 and industry practice require a single lift director to coordinate all movements during a tandem lift to prevent load imbalance or crane overload.

Question 51: Which harmonic order is typically the lowest and most significant harmonic produced by a six-pulse rectifier stage in a wind turbine converter?

11th harmonic (660 Hz)
3rd harmonic (180 Hz)
7th harmonic (420 Hz)
5th harmonic (300 Hz) (Correct answer)

Correct answer: 5th harmonic (300 Hz)

A six-pulse converter produces characteristic harmonics of order 6n±1 (5th, 7th, 11th, 13th…), with the 5th harmonic (300 Hz on a 60 Hz system) being the lowest and largest.

Question 52: A 690 V wind turbine generator output is stepped up to 34.5 kV for collection. What transformer winding configuration is most common for this application?

Delta primary, Wye secondary (Correct answer)
Wye primary (grounded), Delta secondary
Delta-Delta
Wye-Wye

Correct answer: Delta primary, Wye secondary

A Delta-Wye (delta primary, grounded wye secondary) configuration is standard for wind turbine pad-mount transformers, providing grounding on the MV collection side.

Question 53: During a Low Voltage Ride-Through (LVRT) event, what is the wind turbine required to do according to US grid codes?

Remain connected and support the grid with reactive current injection (Correct answer)
Reduce active power to zero and wait for voltage recovery
Trip offline immediately to protect internal components
Switch to islanded operation using local battery storage

Correct answer: Remain connected and support the grid with reactive current injection

US grid codes (FERC Order 661-A) require wind turbines to stay connected during voltage dips and inject reactive current to support grid voltage recovery.

Question 54: A wind turbine main shaft is described as using a 'moment bearing' design. What does this mean?

The bearing housing is bolted directly to the nacelle bedplate moment frame
The bearing is sized to carry bending moments from the rotor overhang in addition to radial and axial forces (Correct answer)
The bearing uses a hydraulic moment arm to adjust preload in service
The main shaft is hollow to reduce bending moment along its length

Correct answer: The bearing is sized to carry bending moments from the rotor overhang in addition to radial and axial forces

A moment bearing is designed to resist the large bending moments created by rotor weight overhang and asymmetric wind loading, carrying combined radial, axial, and moment loads.

Question 55: What is the minimum required Personal Protective Equipment (PPE) when working with hydraulic systems at pressures above 2,000 psi?

Face shield, hydraulic-rated gloves, and appropriate body protection to guard against high-pressure injection injuries (Correct answer)
Chemical-resistant apron only
Standard work gloves and safety glasses only
Hard hat and steel-toed boots only

Correct answer: Face shield, hydraulic-rated gloves, and appropriate body protection to guard against high-pressure injection injuries

High-pressure hydraulic fluid injection injuries are life-threatening; face shields, rated gloves, and body protection are required to prevent penetrating injuries.

Question 56: What is the ASME standard that governs the design, construction, and use of below-the-hook lifting devices used on wind turbine components?

ASME B30.2
ASME B30.9
ASME B30.20 (Correct answer)
ASME B30.10

Correct answer: ASME B30.20

ASME B30.20 specifically covers below-the-hook lifting devices, which include custom lifting beams, spreader bars, and other engineered attachments.

Question 57: When vacuum infusion is used for a blade field repair, the target vacuum level before introducing resin is typically:

−26 inHg (−88 kPa) (Correct answer)
−10 inHg (−33.9 kPa)
−35 inHg (−118 kPa)
−2 inHg (−6.8 kPa)

Correct answer: −26 inHg (−88 kPa)

A vacuum level of approximately −26 inHg (−88 kPa) or higher (closer to full vacuum) is targeted to consolidate dry fiber, remove air, and ensure complete resin wet-out.

Question 58: During PM inspection of the slip ring assembly, a technician finds carbon dust accumulation. What maintenance action is required?

Only clean if visible sparking has been reported
Clean the assembly with approved solvent, inspect brushes for wear, and check contact surface condition (Correct answer)
Leave it as carbon is a normal lubricant
Replace the entire slip ring immediately

Correct answer: Clean the assembly with approved solvent, inspect brushes for wear, and check contact surface condition

Carbon dust buildup must be cleaned to prevent tracking faults; brush wear and contact surface condition must also be assessed to ensure reliable electrical transfer.

Question 59: What is the purpose of an oil cooler in a wind turbine gearbox lubrication system?

Purge water contamination from the sump
Filter abrasive particles from circulating oil
Pressurize oil delivery to splash-lubricated stages
Maintain oil within its optimal viscosity and temperature operating range (Correct answer)

Correct answer: Maintain oil within its optimal viscosity and temperature operating range

An oil cooler dissipates heat generated by gear meshing and bearing friction, keeping oil temperature within the range where viscosity provides adequate film thickness.

Question 60: During PM, the technician performs a 'brake pad thickness measurement' on the rotor disc brake. What happens if the pad is below minimum thickness?

The pad can be shimmed to extend service life
Braking force is reduced and the pad must be replaced immediately before returning the turbine to service (Correct answer)
The SCADA system will compensate with higher pitch angles
Performance is unaffected until the pad is fully worn through

Correct answer: Braking force is reduced and the pad must be replaced immediately before returning the turbine to service

Below-minimum brake pad thickness reduces stopping force and risks brake disc damage; the turbine must be taken out of service until pads are replaced.

NFPA Certified Wind Turbine Technician-I (WTT-I)

The NFPA WTT-I certification validates foundational knowledge of wind turbine components, operations, and safety procedures for entry-level technicians, covering mechanical systems, hydraulics, electrical systems, and working-at-heights safety.

Questions

120 min

Time Limit

70%

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