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Ice Shedding and Ice Throw – Risk and Mitigation

David Wahl Philippe Giguere Wind Application Engineering GE Energy Greenville, SC

Ice Shedding and Ice Throw – Risk andMitigation
Introduction
As with any structure, wind turbines can accumulate ice under certain atmospheric conditions, such as ambient temperatures near freezing (0°C) combined with high relative humidity,freezing rain, or sleet. Since weather conditions may then cause this ice to be shed, there are safety concerns that must be considered during project development and operation. The intent of thispaper is to share knowledge and recommendations in order to mitigate risk. Institut (DEWI), it should be noted that the actual distance is dependant upon turbine dimensions, rotational speed and manyother potential factors. Please refer to the References for more resources. • Physical and Visual Warnings: Placing fences and warning signs as appropriate for the protection of site personnel and thepublic.[4] • Turbine Deactivation: Remotely switching off the turbine when site personnel detect ice accumulation. Additionally there are several scenarios which could lead to an automatic shutdown ofthe turbine: – Detection of ice by a nacelle-mounted ice sensor which is available for some models (with current sensor technology, ice detection is not highly reliable) – Detection of rotor imbalancecaused by blade ice formation by a shaft vibration sensor; note, however, that it is possible for ice to build in a symmetric manner on all blades and not trigger the sensor[2] – Anemometer icing thatleads to a measured wind speed below cut-in • Operator Safety: Restricting access to turbines by site personnel while ice remains on the turbine structure. If site personnel absolutely must access theturbine while iced, safety precautions may include remotely shutting down the turbine, yawing to place the rotor on the opposite side of the tower door, parking vehicles at a distance of at least...