AOC 15 user manual Turbine Test, Heater on, Parking Brake Release

9.0 Wind Turbine Operation 70

The PLC monitors the system parameters continuously as shown in Table 9.1-2. When a system parameter is out of range or a fault has been registered, the PLC takes appropriate action by disconnecting and either parking or freewheeling the wind turbine. Following this, it will continue to monitor the parameters and faults, resetting the system once they have cleared. Rotor over-speed faults and parking brake undercurrent faults require to be reset manually. The turbine TEST/OFF/ON switch must be switched to OFF first and then back to ON; it is the change from OFF to ON that resets the faults. All other faults reset automatically once the cause of the fault has cleared. An optional low power fault is included in some controllers to shut down the wind turbine, should the output drop significantly below the values expected at a given wind speed. This fault resets automatically, unless it has occurred three times within 75 minutes, in which case a manual reset is required.

During any fault related shutdown, the tip and dynamic brakes activate immediately, with the dynamic brake providing a large portion of the braking torque. Application of the parking brake is normally delayed until the rotor has slowed down sufficiently using the tip and the dynamic brakes. During a loss of utility power to the controller, all brakes are applied simultaneously. Thirty three percent of the dynamic brake capacitance is disabled to allow an immediate torque contribution by the parking brake, keeping the overall braking torque within safe limits.

Turbine TEST:

When set to TEST the parking brake, dynamic brake and rotor jog switches can be energized.

9.1.2 Heater ON

The generator winding and the parking brake heaters prevent condensation from collecting on the windings and the parking brake, respectively. They can be activated manually at the operator's discretion when the dew point is high but only when the wind turbine is disconnected from the grid. When the main contactor is closed, the PLC automatically de-energizes the heater circuit. An optional transmission heater can be provided for severe cold weather sites.

9.1.3 Parking Brake Release

The parking brake release switch allows the operator to release the parking brake when the wind turbine is in test mode and no grid faults, over-speed or high winds have been registered. It is not necessary to release the brake manually during normal operation.

NOTICE: Use of the material contained in this document is subject to the warning on page Iv and the disclaimer on page v of this document.

DOC012R02 AOC 15/50 User Manual Nov 2001