SmartScan turbine blade condition monitoring

Smart Fibres presents SmartScan, the high performance, low cost, all optical blade loads monitoring system for wind turbines, providing dynamic measurements of rotor blades root loading throughout their operating lifetime.

With appropriate analysis and data reduction, operators and maintainers can use this root load data in many ways:

Rotorblade condition monitoring

Using rainflow-counting techniques, the loads encountered by the rotor blades can be compared with those predicted by the EIC class of the wind park, leading to a lifetime consumption estimate for each blade. Condition based maintenance and repair regimes can be considered based on this information, offering the potential of reduced cost per kWh through reduced maintenance costs, component failure mitigation, extended service life and increased turbine availability. Various studies have considered the value proposition of such a system. One such study (right) provided an analysis of the payback time for a blade sensor system on a 2MW offshore turbine. Based on the installed cost of the Smart Fibres system, this study suggests a most likely payback within less than 2 years. For larger and offshore turbines, benefits increase sharply leading to even earlier payback. This analysis does not account for the value of the additional capabilities available from the same installed system:

Rotor Imbalance

Detection of non-uniformity in the loads data warns of increasing rotor imbalance, allowing early remedial action to help reduce the possibility of consequential damage to and failure of other drivetrain components.

Blade Damage

Changes in the loads data may indicate gross blade damage, whether through lightning strike, bird collision or degradation of the laminate structure.

Ice Detection

Ice formation leads to changes in the mass and aerodynamic performance of the rotorblades. Data from the loads monitoring system can assist in maximising the availability of turbines in cold regions, whilst reducing the danger of ice shedding.

Independent Blade Pitch Control

Industry experts believe that improvements may be made to blade pitch controller efficacy by using loads data from the individual blades in a closed loop feedback control system. The potential improvements, which increase with larger rotor swept diameters, lead to lower peak and off-axis loading to the blades and all drivetrain and structural components of the turbine. The potential benefits of independent blade pitch control can lead to turbine efficiency increases, reduced component fatigue damage, and greater flexibility in selecting turbine locations.

Blade Testing

The system’s highly accurate, simultaneous dynamic strain measurement of numerous sensors allows for dense instrumentation of blades during design validation or lifetime qualification testing. Appropriate sensor placement can measure primary load cycles as well as stiffness variation, torsion, and integrity of structural joints.

System Specification (typical):

· Number of Sensors 24 (4 strain + 4 temperature * 3 blades)

· Measurement Range +/- 5000 microstrain

· Measurement Resolution < 1 microstrain

· Measurement Rate 250 Hz, all sensors

· Measurement Dynamic Range 27 dB, over 9 automatic gain stages

· Interrogator Mass 1 kg

· Interrogator Dimensions 140 x 110 x 70 mm

· Interrogator Temperature range -15 to +55 °C

· Firmware features

Flapwise and edgewise strain and temperature signals

Flapwise and edgewise root bending moments