Detecting faults in wind turbines
A wind turbine generator fault detection method is described. The method includes obtaining a first signal from a generator of a wind turbine and a second signal from a vibration sensor coupled to the wind turbine, the first signal representing an output current of the generator, and the second signal being a time-sampled signal representing vibrations of a bearing in the wind turbine. Determining a shaft rotation frequency signal from the first signal, the shaft rotation frequency signal representing a time-varying rotational speed of a shaft of the wind turbine. Resampling an envelope of the second signal based on the shaft rotation frequency signal to provide a third signal, the third signal being an angular sampled signal. Detecting, by the at least one processor, a fault in the bearing of the wind turbine by identifying a characteristic signature of a bearing fault in the third signal.
1. A wind turbine monitoring system comprising:
at least one processor; and a data store coupled to the at least one processor having instructions stored thereon which, when executed by the at least one processor, causes the at least one processor to perform operations comprising:
obtaining a first signal from a generator of a wind turbine and a second signal from a vibration sensor coupled to the wind turbine, the first signal representing an output current of the generator, and the second signal being a time-sampled signal representing vibrations of a bearing in the wind turbine;
determining a shaft rotation frequency signal from the first signal, the shaft rotation frequency signal representing a time-varying rotational speed of a shaft of the wind turbine;
resampling an envelope of the second signal based on the shaft rotation frequency signal to provide a third signal, the third signal being an angular sampled signal, wherein resampling the envelope of the second signal comprises:
determining, based on the shaft rotation frequency signal, a phase-time relationship between time steps of the shaft rotation frequency signal and phases of the shaft of the wind turbine, and
generating, based on the phase-time relationship, a resampling vector of time points representing constant phase increments of the shaft of the wind turbine in an angular domain; and
detecting a fault in the bearing of the wind turbine by identifying a characteristic signature of a bearing fault in the third signal.
2. The system of claim 1 , wherein determining the shaft rotation frequency signal from the first signal comprises:
estimating, at each of multiple different time steps, a fundamental frequency of the first signal; and
determining, based on the fundamental frequency of the first signal at each time step, the shaft rotation frequency signal.
3. The system of claim 2 , wherein estimating the fundamental frequency of the first signal at each time step comprises determining, at each time step, a maximum value of a time-frequency distribution of the first signal.
4. The system of claim 2 , wherein determining the shaft rotation frequency signal comprises calculating the shaft rotation frequency signal from the fundamental frequency of the first signal based on a number of poles of the generator of the wind turbine.
5. The system of claim 1 , wherein the operations further comprise determining the envelope of the second signal using a Hilbert transform of the second signal.
6. The system of claim 1 , wherein the operations further comprise oversampling the envelope of the second signal using an oversampling frequency that is greater than a sampling frequency of the second signal.
7. The system of claim 1 , wherein the envelope of the second signal is oversampled by an oversampling frequency that is greater than a sampling frequency of the second signal.
8. The system of claim 1 , wherein resampling the envelope of the second signal comprises:
resampling the envelope of the second signal based on the resampling vector to provide the third signal representing vibrations of the bearing as being sampled at constant phase increments of the shaft of the wind turbine in the angular domain.
9. The system of claim 1 , wherein detecting a fault in the bearing of the wind turbine comprises:
generating an order-domain representation of the third signal; and
identifying the characteristic signature of the bearing fault in the order-domain representation of the third signal.
10. The system of claim 9 , wherein generating the order-domain representation of the third signal comprises performing a fast Fourier transform on the third signal.
11. The system of claim 9 , wherein generating the order-domain representation of the third signal comprises converting the order-domain representation of the third signal into frequency-domain based on a selected reference shaft rotation frequency.
12. The system of claim 10 , wherein the operations further comprise identifying a type of the fault based on the characteristic signature.
13. The system of claim 12 , wherein the type of the fault comprises one of an inner race fault, an outer race fault, a cage fault relative to an outer bearing ring; and a cage fault relative to an inner bearing ring.
14. The system of claim 1 , wherein the operations further comprise providing, for display to a user, data indicating the fault in the bearing of the wind turbine.
15. At least one non-transitory computer readable storage device storing instructions that, when executed by at least one processor, cause the at least one processor to perform operations comprising:
obtaining a first signal from a generator of a wind turbine and a second signal from a vibration sensor coupled to the wind turbine, the first signal representing an output current of the generator, and the second signal being a time-sampled signal representing vibrations of a bearing in the wind turbine;
determining a shaft rotation frequency signal from the first signal, the shaft rotation frequency signal representing a time-varying rotational speed of a shaft of the wind turbine;
resampling an envelope of the second signal based on the shaft rotation frequency signal to provide a third signal, the third signal being an angular sampled signal, wherein resampling the envelope of the second signal comprises:
determining, based on the shaft rotation frequency signal, a phase-time relationship between time steps of the shaft rotation frequency signal and phases of the shaft of the wind turbine, and
generating, based on the phase-time relationship, a resampling vector of time points representing constant phase increments of the shaft of the wind turbine in an angular domain; and
detecting a fault in the bearing of the wind turbine by identifying a characteristic signature of a bearing fault in the third signal.
16. A wind turbine generator fault detection method executed by at least one processor, the method comprising:
obtaining a first signal from a generator of a wind turbine and a second signal from a vibration sensor coupled to the wind turbine, the first signal representing an output current of the generator, and the second signal being a time-sampled signal representing vibrations of a bearing in the wind turbine;
determining, by the at least one processor, a shaft rotation frequency signal from the first signal, the shaft rotation frequency signal representing a time-varying rotational speed of a shaft of the wind turbine;
resampling, by the at least one processor, an envelope of the second signal based on the shaft rotation frequency signal to provide a third signal, the third signal being an angular sampled signal, wherein resampling the envelope of the second signal comprises:
determining, based on the shaft rotation frequency signal, a phase-time relationship between time steps of the shaft rotation frequency signal and phases of the shaft of the wind turbine, and
generating, based on the phase-time relationship, a resampling vector of time points representing constant phase increments of the shaft of the wind turbine in an angular domain; and
detecting, by the at least one processor, a fault in the bearing of the wind turbine by identifying a characteristic signature of a bearing fault in the third signal.
17. The method of claim 16 , wherein determining the shaft rotation frequency signal from the first signal comprises:
estimating, at each of multiple different time steps, a fundamental frequency of the first signal; and
determining, based on the fundamental frequency of the first signal at each time step, the shaft rotation frequency signal.
18. The method of claim 17 , wherein estimating the fundamental frequency of the first signal at each time step comprises determining, at each time step, a maximum value of a time-frequency distribution of the first signal.
19. The method of claim 17 , wherein determining the shaft rotation frequency signal comprises calculating the shaft rotation frequency signal from the fundamental frequency of the first signal based on a number of poles of the generator of the wind turbine.
20. The method of claim 16 , wherein resampling the envelope of the second signal comprises:
resampling the envelope of the second signal based on the resampling vector to provide the third signal representing vibrations of the bearing as being sampled at constant phase increments of the shaft of the wind turbine in the angular domain.