IEC 61400-12

IEC 61400 is the family of international standards covering wind turbine design, certification, and testing. Part 12 governs power performance measurement: how wind speed is measured and at what height, how the measurement sector is selected to avoid obstacles and wake, how data is binned by wind speed, how air density normalization is applied, and how uncertainty is reported.

Its purpose is commercial as much as technical. A warranted power curve is a contractual promise, and without a shared procedure for testing it, buyer and supplier would measure differently and disagree permanently. The standard defines a reference measurement, historically against a met mast in free-stream flow, with remote sensing now accepted in defined circumstances.

A formal test under the standard is expensive and is normally run on a small number of machines at commissioning, or when a dispute arises. It answers whether a turbine meets its specification under controlled conditions on a specific day. It is not, and was never intended to be, a method for watching an entire operating fleet continuously.

That is the gap continuous performance analysis fills, and the distinction is worth keeping clear. A standardized test establishes contractual compliance; a normal behavior model built from a machine's own history establishes whether it is still producing what it was producing last year. Both are legitimate, and they answer different questions.