Method and system for monitoring sub-synchronous torsional oscillations of a shaft line of a steam turbine
First Claim
1. A method for monitoring sub-synchronous torsional oscillations of a shaft line of a steam turbine, the method comprising:
- measuring a rotational speed of the shaft line over a period of time (T0) and generating, from the measured rotational speed, a signal representative of the rotational speed over the period of time (T0);
performing a spectrum analysis on the signal to determine an amplitude (Ai) of variation of the rotational speed for at least one frequency (fri);
comparing the amplitude (Ai) with at least two of predetermined amplitude thresholds (Ai1, Ai2) for the at least one frequency (fri), wherein the at least two of predetermined amplitude thresholds comprise a lower (Ai1) predetermined amplitude threshold and a higher (Ai2) predetermined amplitude threshold;
generating an alert signal when the amplitude (Ai) is lower than the lower (Ai1) predetermined amplitude threshold and higher than the higher (Ai2) predetermined amplitude threshold for the at least one frequency (fri);
receiving the alert signal at a control unit; and
partially closing a valve by the control unit based on the alert signal for controlling an amount of steam supplied to the steam turbine, when the amplitude (Ai) is between the higher (Ai2) predetermined amplitude threshold and the lower (Ai1) predetermined amplitude threshold.
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Accused Products
Abstract
A method for monitoring sub-synchronous torsional oscillations of a shaft line of a steam turbine includes measuring a rotational speed of the shaft line over a period of time and generating, from the measured rotational speed, a signal representative of the rotational speed over the period of time. The method further includes performing a spectrum analysis on the signal to determine, for at least one given frequency, an amplitude of variation of the rotational speed at the given frequency, comparing the amplitude with at least one predetermined amplitude threshold for the frequency, and generating an alert signal if the amplitude exceeds at least one predetermined amplitude threshold.
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Citations
15 Claims
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1. A method for monitoring sub-synchronous torsional oscillations of a shaft line of a steam turbine, the method comprising:
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measuring a rotational speed of the shaft line over a period of time (T0) and generating, from the measured rotational speed, a signal representative of the rotational speed over the period of time (T0); performing a spectrum analysis on the signal to determine an amplitude (Ai) of variation of the rotational speed for at least one frequency (fri); comparing the amplitude (Ai) with at least two of predetermined amplitude thresholds (Ai1, Ai2) for the at least one frequency (fri), wherein the at least two of predetermined amplitude thresholds comprise a lower (Ai1) predetermined amplitude threshold and a higher (Ai2) predetermined amplitude threshold; generating an alert signal when the amplitude (Ai) is lower than the lower (Ai1) predetermined amplitude threshold and higher than the higher (Ai2) predetermined amplitude threshold for the at least one frequency (fri); receiving the alert signal at a control unit; and partially closing a valve by the control unit based on the alert signal for controlling an amount of steam supplied to the steam turbine, when the amplitude (Ai) is between the higher (Ai2) predetermined amplitude threshold and the lower (Ai1) predetermined amplitude threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A system for monitoring sub-synchronous torsional oscillations of a shaft line of a steam turbine, the system comprising:
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a speed measurement device configured to measure a rotational speed of the shaft line over a period of time (T0), and to generate, from the measured rotational speed, speed values forming a signal representative of the rotational speed over the period of time (T0); an analysis unit configured to perform a spectrum analysis on the signal and to determine an amplitude (Ai) of variation of the rotational speed for the at least one frequency (fri), the analysis unit being further configured to compare the amplitude (Ai) with at least two of predetermined amplitude thresholds (Ai1, Ai2) for the at least one frequency (fri), wherein the at least two of predetermined amplitude thresholds comprise a lower (Ai1) predetermined amplitude threshold and a higher (Ai2) predetermined amplitude threshold and to generate an alert signal when the amplitude (Ai) is lower than the lower (Ai1) predetermined amplitude threshold and higher than the higher (Ai2) predetermined amplitude threshold; and a control unit on receiving the alert signal, partially closes a valve for controlling an amount of steam supplied to the steam turbine, when the amplitude (Ai) is between the higher (Ai2) predetermined amplitude threshold and the lower (Ai1) predetermined amplitude threshold. - View Dependent Claims (15)
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Specification