After the connection of a Wind Farm to the grid several parameters are used to analyze the smooth operation of the installation.
The more relevant are:
Capacity Factor
Is a parameter used frequently in power producing plant. A high capacity factor means that the plant is working almost continuously (for instance a nuclear plant), while a low capacity factor may characterize a power plant working only in peak hours (like some hydro plants).
In the case of wind farms, capacity factor depends more on the wind that on the needs of the grid.
To be economically reasonable, a wind farm needs to have a capacity factor of more than 25%. Translated in hours, it would be around 2190 equivalent hours.
This parameter is probably too “global”, as it doesn’t add information about why the wind farm was not producing: was it for a low wind, for a technical problem of the WTG, for a disconnection from the grid?
Or maybe it is due to a scheduled maintenance or to the wind sector management (the automatic planned disconnection of some WTGs in particular wind conditions)?
Technical Availability
This is easily defined: basically is the ratio between the hours the WTG was available for production an the total number of hours in the considered period. If there is a fault in the grid, or if wind condition is above or below the maximum, it doesn’t count as “unavailability”.
Production Availability
This is parameters start to be interesting from an economical point of view: is the ratio between the total number of hours producing and the hours in the considered period. It will be less than 1 due to grid disconnections, WTG problems and wind outside the operational limits.
Effective Availability
This parameter give a very solid information about the quality of the turbine, and the “real” availability: is the ratio between the hours of production and the hours of wind speed between the operational limits, minus the hours disconnected by the grid (for a grid problem or order) minus the justified stops (for visits, preventive maintenance, etc.)