Patent ID: 8286494

Claim:
A method for monitoring blade frequencies of a wind turbine, comprising: providing a first bolt gauge, which includes a built-in load cell; providing a rotating hub including a pitch bearing, which includes an inner ring and an outer ring, the outer ring is connected to a hub by a plurality of bolts, each of which is secured by a tightening means, the inner ring is connected to a plurality of rotating blades by a plurality bolts, each of which is secured by a tightening means, the first bolt gauge positioned on a first bolt of the plurality of bolts of the outer ring between the pitch bearing and the tightening means of the first bolt, or the first bolt gauge positioned on a first bolt of the plurality of bolts of the inner ring between the pitch bearing and the tightening means of the first bolt, or detecting, a load or pressure via the bolt gauge; receiving an electrical signal for the detected load or detected pressure which is used to measure the vibrations and/or frequencies of the plurality of rotating blades; calculating a new frequency for the rotating blades by comparing each blade frequency to the other blade frequencies; and using this comparing to calculate the change in each blade frequency.