The subject of wind turbine maintenance is becoming increasingly important, especially as growing numbers of turbines are now falling outside of the original manufacturers’ warranties.

Ideally, wind farm operators want to minimise maintenance costs and maximise turbine availability and although these opposing demands can be met, they depend on the continued reliability of all turbine systems.

It can, however, often be the failure of the smallest of components that cause the most downtime, with the failure of electrical and sensor parts causing just as much downtime as the failure of gearboxes or hydraulic systems.

Smaller components important

It is vital that a catalogue of reliable components and practices for the effective maintenance of wind turbines can be established. As with any other engineering industry, the goal for the maintenance of wind turbines is to set in place a series of procedures that will increase efficiency by preventative measures. If components can be introduced that are highly unlikely to cause failures and stoppages, loss of electricity sales can be avoided.

The need to reduce maintenance is especially urgent when you consider the environments in which wind turbines are situated. Accessing a wind turbine nacelle is typically difficult at the best of times but when the location of some wind turbines is taken into account, such as offshore windfarms that cannot even be visited until a repair vessel has been organised, the importance of avoiding unscheduled maintenance and extending times between scheduled maintenance is only too clear.

The best way to sidestep such problems is to specify turbines with devices that ensure reliable function for extended periods under extreme operating conditions from the outset or, where existing turbines are concerned, at the earliest opportunity.

To meet this need, manufacturers are developing pressure switches and transducers that ensure turbines function reliably for extended periods and under extreme operating conditions. Pressure switches and transducers are key components in turbines, being used to monitor and control hydraulic pitch, yaw and braking systems, and failure of a pressure component can potentially cause major damage.

The good news is that such components are increasingly being made available in robust, exceptionally reliable form and to a wide range of specifications, defending systems from failure and operators from the costs that even small unplanned maintenance periods can create.

Pressure sensors

In a typical wind turbine, key actions are managed via a series of pressure sensors to ensure safe and efficient operation, for example, the management of the pitch control system. In order to optimise the productivity of a wind turbine, its power output must be maximised at any given wind speed and this is achieved by adjusting the angle at which the edge of the blade cuts into the wind.

Pressure transducers play an important role in ensuring swift changes in the pitch of the blades, changes that can also prevent the turbine from damage; if the wind speed rises above the turbine’s rate capacity, the blades must be edged parallel with the wind, or ‘furled’, to avoid any potential damage.

Hydraulic pitch control, a system that uses fewer components than a mechanical alternative and thus satisfies the need for reduced maintenance, is the most common method of protecting the blades as described above, since it responds more quickly and minimises the likelihood of overload.

Hydraulic pitch control is typically accompanied by hydraulic yaw control, a system that maximises power output by positioning the rotor to face the wind and which is also controlled by pressure sensors.

Gems is an example of a manufacturer that sells a wide range of pressure switches and transducers, and level switches, for use in hydraulic systems.

Typically, for wind turbines, these include pressure switches for use on the main manifold and system pumps, and on accumulators and yaw control and braking systems, plus sensors for monitoring lubricant pressures in gearboxes and levels in hydraulic reservoirs.

In each case, switches and transducers are engineered to ensure high overpressure capability, to withstand a wide range of extreme temperatures and vibration, and to offer protection against high levels of electromagnetic interference.

Now that wind power is no longer seen as an optional alternative but a key component in the portfolio of sustainable technologies that will be fulfilling our demand for energy in the future, the need to support the industry with the latest innovative and robust technology is greater than ever before. Sensors are playing an important role in managing the costs of wind energy production to boost the economic and environmental benefits of this vital technology.

About: Mike Powers is Product Marketing Director for Gems Sensors and Controls.