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SCADA and instruments

A vital element of the wind farm is the SCADA system.  This system acts as a ‘nerve centre’ for the project.  It connects the individual turbines, the substation and meteorological stations to a central computer.  This computer and the associated communication system allow the operator to supervise the behaviour of all the wind turbines and also the wind farm as a whole.  It will keep a record on a 10 minute by 10 minute basis of all the activity, and allows the operator to determine what corrective action, if any, needs to be taken.  It also records energy output, availability and error signals, which will act as a basis for any warranty calculations and claims.  The SCADA system also has to implement any requirements in the connection agreement to control reactive power production, to contribute to network voltage or frequency control, or to limit power output in response to instructions from the network operator.

The SCADA computer communicates with the turbines via a communications network, which is almost always implemented by optical fibres.  Often the fibre optic cables are installed by the electrical contractor, then tested and terminated by the SCADA supplier.

The SCADA system is usually provided by the turbine supplier, for contractual simplicity.  There is also a market for SCADA systems from independent suppliers.  The major advantages of this route are claimed to be:

• Identical data reporting and analysis formats, irrespective of turbine type.  This is important for wind farm owners or operators who have projects using different wind turbines
• Transparency of calculation of availability and other possible warranty issues

In addition to the essential equipment needed for a functioning wind farm, it is also advisable, if the project size can warrant the investment, to erect some permanent meteorological instrumentation on met masts.  This equipment allows the performance of the wind farm to be carefully monitored and understood.  If the wind farm is not performing according to its budget it will be important to determine whether this is due to poor mechanical performance, or less-than-expected wind resource.  In the absence of good quality wind data on the site it will not be possible to make this determination.  Large wind farms therefore usually contain one or more permanent meteorological masts, which are installed at the same time as the wind farm.