Page 14 - North American Clean Energy May June 2018 Issue

wind power
Space is very limited inside the hub, making it more difficult to do the troubleshooting of the pitch control system.
Extreme Weather Conditions vs. Proportional Pitch Control Valves
by Scott Smith
In many instances, performance of the hydraulic pitch control is scrutinized in suitable weather conditions. However, these control systems are exposed to a variety of extreme weather conditions that can greatly a ect both pitch performance, and longevity of the control components.
High Wind Speed will create high levels of vibration in the pitch
valve as it rotates in the hub of the turbine. e onboard electronics are susceptible to these rotational forces, subjecting the electronic driver card and enclosure to G-forces that loosen screws and wire connections; this results in loss of rotational position control of the blade.
Troubleshooting a fault or failure in wind turbines is not a quick and easy task. e tower climb and work process must be planned, and parts gathered; a climb safety meeting must be held before travel to the down turbine is even started. is controlled process can take many hours.
Once uptower and inside the nacelle – and especially the hub – space is
very limited, making it more di cult to diagnose the problem. Changing a
As in any hydraulic system, hydraulic pitch control systems experience the typical performance issues related to uid cleanliness, temperature, and viscosity. Wind turbines, however, are not your typical industrial or mobile application for these components. e majority of hydraulic pitch control turbines over 1mw have a proportional control valve manifold, hard-mounted to the pitch ram inside the hub. e hub, which rotates with
the blades, has much higher exposure to the external weather conditions; its only protection is a berglass nose cone that is not sealed. It’s not the easiest environment in which to function.
With turbines installed all over the world, in ever-changing climates, weather conditions can have a devastating e ect on performance and life of the proportional pitch control valve and system. Four primary weather conditions have a profound e ect on the life of the pitch control components: Extreme Cold, Heat, Humidity, and High Wind Speed.
Cold can cause loss of spool seal integrity,
as well as increased spool wear due to low viscosity. Extreme cold can also a ect control wiring and connections.
Heat creates low viscosity concerns, increasing wear, and reducing spool life. Varnishing can also result in spool sticking issues that can a ect the proportional-integral-derivative (PID) control loop.
Humidity will cause corrosion in coil pin connections, or any type of electronic connection that is not well sealed. Ultimately, this will result in accuracy problems in the rotational PID loop, often causing a fault in the turbine control system.
This 50-liter pitch package to decrea
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valve was designed with a more robust electronic se failure rates in harsh operating environments.