Gas turbine engine with active protection against pulsations and method of operating the same

Abstract

The present invention relates to a gas turbine engine having active protection against pulsations and a method of operating the same. A gas turbine engine includes a burner assembly (3) having a plurality of burner units (8) and a control system (3) configured to control the air supply and the fuel supply to the burner assembly (3). The control system (3) includes pulsation sensors (12) coupled to respective burner units (8) to provide a pulsation signal (P N (t)) and a processing unit (13) coupled to the pulsation sensors (12) to receive the pulsation signal (P N (t)). The processing unit (13) determines a working time series (TSW N ) of spectral parameters (A1; A1, A2; F1) of at least one of the pulsation signals (P N (t)), and selectively activates a protection measure based on the working time series (TSW N ) and an activation criterion. In response to the activation of the protection measure, the control system (3) modifies the air supply and / or the fuel supply to the burner assembly (3).

Description

[0001] Cross - reference to related applications

[0002] This patent application claims the benefit of priority of European Patent Application No. 19220209.1, filed on December 31, 2019, the entire disclosure of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a gas turbine engine having active protection against pulsations and to a method of operating a gas turbine engine. Background art

[0004] It is well known that in the past few years, the flexible control of gas turbines in power generation equipment has become the most important goal. On the one hand, in fact, the awareness of environmental risks has prompted regulations that set increasingly strict requirements. On the other hand, the organization of the modern power market and the continuously changing demands do not allow the operation of power generation equipment under constant load conditions. Instead, the need to meet demand fluctuations (including sudden increases or decreases) and contribute to the control of the grid frequency requires flexible operation.

[0005] However, such flexible operation increases the risk of the gas turbine suffering critical conditions because a wide operating range has to be considered. In addition, the aging of components may cause a drift of critical conditions, such that dangerous vibration states may occur during the service life of the machine due to deviation from the design characteristics. In fact, in the field of gas turbines, it is well known that mechanical and thermo - acoustic vibrations are generated under different operating conditions. Such conditions depend on the response of the complex structure of the gas turbine and can vary widely depending on the type and size of the gas turbine and also change over time due to, for example, the aging of components. During the design and test steps of the gas turbine, oscillating operating conditions and frequencies may become evident, and thus protective measures such as mufflers may be provided. However, when the conditions change, such measures may become ineffective.

[0006] Therefore, poor combustion conditions may cause serious damage to the machine structure because certain parts (such as thermal barrier coatings) may be vulnerable to vibrations and thermo - acoustic pulsations, especially at certain frequencies. As a result, the frequency of maintenance required is higher than desired. Moreover, despite regular maintenance, turbine parts may lose their effectiveness and may no longer be able to perform their functions adequately. For example, in the case of thermal barrier coatings, the loss of effectiveness may lead to serious and even irreversible damage to the metal components that are no longer adequately protected.

[0007] Other serious events, such as excessive levels of pollutant emissions, may not pose a danger to the machine itself, but should be avoided anyway to comply with laws and regulations and also because the efficiency of the machine is significantly affected.

[0008] Therefore, there is a general desire to improve the protection of a gas turbine against critical operating conditions under which dangerous vibrations and / or thermoacoustic pulsations may occur. Summary of the Invention

[0009] Accordingly, it is an object of the present invention to provide a gas turbine engine and a method of operating a gas turbine which allow overcoming or at least alleviating the above limitations.

[0010] According to the present invention, there is provided a gas turbine engine comprising:

[0011] a burner assembly having a plurality of burner units; and

[0012] a control system configured to control the air supply and the fuel supply to the burner assembly;

[0013] The control system comprises:

[0014] a pulsation sensor coupled to a respective burner unit and configured to provide a pulsation signal from the respective burner unit; and

[0015] a processing unit coupled to the pulsation sensor to receive the pulsation signal and configured to:

[0016] determine a working time series of spectral parameters of at least one of the pulsation signals; and

[0017] selectively activate a protection measure based on the working time series and an activation criterion.

[0018] Monitoring the spectral parameters of the pulsation signal allows identification of adverse oscillation phenomena at a very early stage and is insensitive to the aging of components. More precisely, the monitoring performed by the control system can effectively identify the early occurrence of adverse phenomena, regardless of whether such phenomena are associated with known critical conditions or are caused by unpredictable events such as aging.

[0019] The protection measure can change the operating conditions of the gas turbine by modifying the air and / or fuel supply so as to reduce the influence of the oscillation phenomenon. In some cases, very small changes may be sufficient to bring the gas turbine to a safe operating condition with a low risk of dangerous oscillations. Additionally, when a distinct trend is shown by the time series, the protection measure can be triggered, thus avoiding unnecessary intervention in response to fluctuations (such as statistical errors) that do not actually reflect critical conditions. The control system can be configured to respond to the activation of the protection measure by directly modifying the air supply and / or fuel supply to the burner assembly, or alternatively by sending an alert or warning message to prompt the operator to take action, such as changing the operating set point and thus changing the air supply and / or fuel supply.

[0020] According to one aspect of the present invention, the activation criterion includes a value criterion defined by a non-permissible value range of spectral parameters, and a time criterion coordinated based on the persistence of the spectral parameters within the non-permissible value range.

[0021] The use of the combined criterion helps to reduce the activation of unnecessary protective measures.

[0022] According to one aspect of the present invention, the spectral parameters include at least one peak amplitude within a corresponding programmed frequency range, and the processing unit is further configured to compare the working time series of the peak amplitudes with corresponding independent amplitude thresholds, and the non-permissible value range includes peak amplitude values greater than the independent amplitude thresholds.

[0023] In this way, the strongest oscillations can be easily identified and distinguished from background noise that is not an indicator of potential dangerous conditions, thus allowing the timely activation of protective measures whenever critical oscillations occur at any monitored burner unit.

[0024] According to one aspect of the present invention, the spectral parameters include a plurality of peak amplitudes within corresponding programmed frequency bands for each of at least one pulsating signal, and the processing unit is further configured to compare the combination of the working time series of the peak amplitudes with a combined amplitude threshold, and the non-permissible value range includes combined values greater than the combined amplitude threshold.

[0025] Monitoring the combination of peak amplitudes in multiple frequency bands can reveal the effects of non-linear coupling of acoustic modes that might otherwise be missed. Thus, the protection is further improved.

[0026] According to one aspect of the present invention, the spectral parameters include at least one peak frequency of corresponding peak amplitudes, and the processing unit is further configured to compare the working time series of the peak frequencies with a lower frequency threshold and an upper frequency threshold, and the non-permissible value range includes the frequency band defined by the lower frequency threshold and the upper frequency threshold.

[0027] When the oscillation approaches the eigenfrequency of the structure, the structure of the burner assembly may sometimes exhibit resonance behavior even in a very narrow band. Thus, adverse oscillations can even be triggered by relatively small amplitudes in the critical band, i.e., relatively small oscillations near the eigenfrequency may amplify and cause resonance phenomena. Monitoring the oscillation peak frequency allows preventing the gas turbine from remaining in operating conditions that may trigger resonance. In many cases, making a small adjustment to the air and / or fuel supply may change the operating conditions sufficiently to avoid resonant oscillations.

[0028] According to one aspect of the present invention, the processing unit is configured to determine the original time series of the spectral parameters from the pulsating signal and determine the working time series from the corresponding original time series by low-pass filtering.

[0029] Accordingly, less significant false positives and short-lived transients can be ignored, and unnecessary activation of protective measures can be avoided.

[0030] According to one aspect of the present invention, the time criteria include at least one of the following:

[0031] Spectral parameters of the operating time series continuously remain within a non-permissible value range for at least a first time interval;

[0032] Spectral parameters of the operating time series continuously or intermittently remain within a non-permissible value range within an inspection window for at least a cumulative second time interval;

[0033] A time counter reaches a count threshold, and the counter is incremented by a processing unit when the spectral parameters of the operating time series are within a non-permissible value range, and remains unchanged or is decremented by the processing unit when the spectral parameters of the operating time series are outside the non-permissible value range.

[0034] Accordingly, appropriate time criteria can be made available, and appropriate time criteria can be used according to design preferences in order to achieve a balance between timely activation of protective measures and effective rejection of false positives.

[0035] According to one aspect of the present invention, there is also provided a method of operating a gas turbine including a burner assembly having a plurality of burner units and a control system configured to control an air supply and a fuel supply to the burner assembly;

[0036] The method includes:

[0037] Providing a pulsation signal in response to pulsations at a corresponding burner unit;

[0038] Determining an operating time series of spectral parameters of at least one of the pulsation signals; and

[0039] Selectively activating a protective measure based on the operating time series and an activation criterion;

[0040] Wherein activating the protective measure includes modifying the air supply and / or the fuel supply to the burner assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will now be described with reference to the drawings, which show some non-limiting embodiments of the present invention, in which:

[0042] - Figure 1 is a simplified block diagram of a gas turbine engine according to an embodiment of the present invention;

[0043] - Figure 2 is Figure 1 a schematic front view of a burner assembly of the gas turbine engine of

[0044] - Figure 3 is a flowchart of a method performed by a control system of a gas turbine Figure 1 in accordance with an embodiment of the present invention;

[0045] - Figure 4 is a diagram showing spectral quantities used in the method Figure 3 of;

[0046] - Figure 5 and Figure 6 are diagrams showing time series used in the method Figure 3 of;

[0047] - Figures 7 - 9 is a diagram showing time series and alternative activation criteria available in the method Figure 3 of;

[0048] - Figure 10 is a diagram showing time series used in a method performed by a control system of a gas turbine Figure 1 in accordance with another embodiment of the present invention;

[0049] - Figure 11 is a diagram showing activation criteria available in the method Figure 10 of;

[0050] - Figure 12 is a diagram showing time series used in a method performed by a control system of a gas turbine Figure 1 in accordance with another embodiment of the present invention. DETAILED DESCRIPTION

[0051] Referring to Figure 1 , numeral 1 generally defines a gas turbine installation, including a gas turbine engine 2 and a control system 3. The gas turbine engine 2 in turn includes a compressor 4, a burner assembly 5, and an expansion section or turbine 6, all of which extend about an axis A. The compressor 4 and the turbine 6 share a common rotor 7.

[0052] The compressor 4 supplies an air flow drawn in from the outside to the burner assembly 5. The air supply to the compressor 4 can be controlled by the control system 3 by adjusting the orientation of the inlet guide vanes 6 of the compressor 4.

[0053] The burner assembly 5 (e.g., a can-type or can-annular burner) is provided with a plurality of burner units 8, which are circumferentially distributed about the axis A, as Figure 2is schematically shown. The burner unit 8 mixes air from the compressor 4 and fuel from the fuel supply line 9 to form a mixture for combustion. The fuel can be gaseous, such as natural gas or synthesis gas, or liquid, such as diesel. The gas turbine engine 2 can be configured to use different types of fuels, both gaseous and liquid. The fuel supply can be controlled by the control system 3 via the fuel valve system 10.

[0054] The turbine 6 receives and expands the hot gas stream from the burner assembly 5 to extract mechanical work, which is transferred to an external user, typically a generator, not shown here.

[0055] The control system 3 includes a pulsation sensor 12, a processing unit 13, and a controller 14. The pulsation sensor 12 can be, for example, a pressure sensor or an optical sensor.

[0056] The pulsation sensor 12 is coupled to the respective burner unit 8 and is configured to provide a pulsation signal P N (t) in response to pulsations at the respective burner unit 8. In one embodiment, each burner unit 8 is provided with a respective pulsation sensor 12, thus providing pulsation signals P 1 (t), P 2 (t), …, PNC(t), where NC is the number of burner units 8 of the burner assembly 5. However, according to design preferences, other configurations with pulsation sensors 12 associated only with selected burner units 8 can be used. Any kind of pulsation sensor capable of detecting pressure oscillations inside the burner unit 8 and / or mechanical vibrations of the structure of the burner unit 8 can be used for this purpose. For example, piezoelectric pressure or vibration sensors or strain gauges can be used. The pulsation sensor 12 can be provided with detection electronics to provide the pulsation signal P N (t) in a form determined according to design preferences (e.g., as a voltage signal). For example, piezoelectric sensors typically provide a charge signal as an output. Therefore, the detection electronics can include a charge amplifier to convert the charge output of the piezoelectric sensor into a voltage output.

[0057] The processing unit 13 is coupled to the pulsation sensor to receive the pulsation signal P N (t). Through the Figure 3 process shown in N the processing unit 13 is configured to determine the working time series TSW N of the spectral parameters of the pulsation signal P Figures 4 - 6 (see NThe activation criteria selectively activate the protection measures. In one embodiment, the protection measures may include an automatic response of control system 3. In this case, the control system is configured to modify the air supply and / or fuel supply to the burner assembly in response to activation of the protection measures. The protection measures may also include sending an alert or warning message to prompt the operator to take measures, such as changing the operating set point and thus changing the air supply and / or fuel supply.

[0058] Generally, a time series is a sequence of data points indexed in chronological order. The time series may be a data sequence with equal time intervals and thus is a discrete-time data sequence. As understood herein, the working time series is a time series of spectral parameters used in processing unit 13 for pulsation protection purposes. As understood herein, the original time series is a time series directly obtained as the values of spectral parameters calculated at successive time points. In other words, the pulsation signals P 1 (t), P 2 (t), …, PNC(t) are spectrally analyzed, and the spectral parameters of interest are extracted. Successive values of the spectral parameters are extracted at each time point defining the original time series. The working time series may be identical to the original time series or may be derived from the original time series by processing. The processing may include, for example, filtering and defining such that the resulting working time series is more suitable for implementing pulsation protection.

[0059] Specifically, processing unit 13 iteratively converts the received analog pulsation signal P N (t) into the corresponding digital signal ( Figure 3 , block 100), and applies a fast Fourier transform (block 110) to determine the spectral sequence for each pulsation signal P N (t). At each iteration, processing unit 13 extracts selected spectral parameters of the spectrum (block 120; also see Figure 4 , where the extracted spectral parameter is the peak amplitude A 1 , A 2 ), and updates the working time series TSW N based on the extracted spectral parameters (blocks 130 - 140). In other words, each time series TSW N is based on a sequence of values of a corresponding one of the spectral parameters as determined by processing unit 13 in a subsequent iteration. The values of the working time series TSW N need not be the exact values of the spectral parameters, and processing may be added. In one embodiment, for example, processing unit 13 updates (block 130) the original time series TSR N of the spectral parameters of the pulsation signal P N (i.e., the sequence of exact digital values of the spectral parameters, see Figure 5 of the peak amplitude A 1), and determine the working time series TSW from the corresponding original time series TSR by low-pass filtering N Determine the working time series TSW N (block 140; also see Figure 6 The peak amplitude A of the filtered 1 ). Thus, the working time series TSW N is smoothed to reduce false positives and avoid unnecessary activation of protection measures. However, in other embodiments, the original time series of spectral parameters can be directly used as the working time series TSW N .

[0060] In addition, at each iteration, the processing unit 13 checks the updated time series TSW with respect to the activation criteria N (block 150), and if the activation criteria are met, activates the protection measures (block 150, output yes; block 160). Then, a new iteration of the process is performed by the processing unit 13 through the steps of A / D conversion, fast Fourier transform, spectral parameter extraction, update of the working time series TSW N and checking of the activation criteria (blocks 100 - 150). If the activation criteria are not met (block 150, output no), the processing unit 13 directly starts a new iteration of the process

[0061] The activation criteria can include a combination of a value criterion and a time criterion. The value criterion is defined by a range of values not allowed for the spectral parameters, such as the time series being within a prohibited region. The time criterion is based on the persistence of the spectral parameters within the range of values not allowed

[0062] The time criterion can include one or more of the following conditions

[0063] - The spectral parameters of the working time series TSW N continuously remain within the range of values not allowed for at least a first time interval T 1 (in the example of Figure 7 , which refers to the working time series TSW of the peak amplitude A 1 , the range of values not allowed IRVI includes a peak amplitude value region greater than the independent amplitude threshold ATH N ); N );

[0064] - The spectral parameters of the working time series TSW N continuously or intermittently remain within the range of values not allowed IRVI within the inspection window W for at least a cumulative second time interval T 2 ( Figure 8 , where CT is the cumulative time in the prohibited region within the inspection window W); and

[0065] - The time counter TC reaches a count threshold C 0, the time counter TC is incremented by the processing unit 13 when the spectral parameter of the working time series TSW N is within the inadmissible value range IRVI, and otherwise remains unchanged ( Figure 9 , solid line) or is decremented ( Figure 5 , dashed line).

[0066] The protective measures may include changing the operating conditions of the gas turbine engine 2. To this end, the processing unit 13 may adjust the setpoint of the controller 14, whereby the control system 3 modifies the air supply and / or fuel supply to the burner assembly 5 in response to the activation of the protective measures.

[0067] In one embodiment, the spectral parameter includes at least one peak amplitude A 1 ( Figures 4 - 6 ). As understood herein, "peak amplitude" refers to the amplitude of the spectral peak in one or more given monitoring frequency bands, in which dangerous pulsations may be expected. The spectral peak is typically much larger than the average spectral amplitude and the local peak amplitude outside the monitoring frequency band. In Figure 4 's example, a first peak amplitude A 1 and a second peak amplitude A 2 are extracted in the first monitoring band B 1 and the second monitoring band B 2 respectively. However, the detection of the peak amplitude need not be limited to a specific band. For example, in one embodiment, all peaks having an amplitude exceeding a threshold may be detected. The threshold may be adaptively set, for example, according to the average value and standard deviation of the spectral values. Each frequency corresponding to the respective peak and peak amplitude is defined as the peak frequency of the respective peak. The processing unit 13 is further configured to compare the working time series TSW 1 of the subsequent value of the peak amplitude A N with the corresponding independent amplitude threshold ATH N . In this embodiment, the inadmissible value range IRVI includes peak amplitude values greater than the independent amplitude threshold ATH N . The processing unit 13 may be configured to extract peak amplitudes from multiple programmed frequency bands. In one embodiment, each peak amplitude is independently monitored for activation criteria via the respective working time series TSW N .

[0068] The monitoring may extend to all burner units 8, or be limited to one or more burner units 8, which may be considered more critical, for example, from a design perspective. For example, when the activation criteria for at least one burner unit 8 are met, the protective measures may be activated, thus providing effective protection for each burner unit 8.

[0069] In one embodiment, each burner unit 8 is provided with a pulsation sensor 12, which supplies a respective pulsation signal P N(t). The processing unit 13 is configured to also determine one or more azimuth components of order M from the pulsation signal P N (t) (up to NC, where NC is the number of burner units 8 in the burner assembly 5), and compare the spectral parameters (such as the amplitude peak and / or peak frequency in a given band) of the azimuth components with the corresponding thresholds (amplitude threshold, upper frequency threshold, and lower frequency threshold respectively). The azimuth components of order M are defined as being

[0070]

[0071] where NC is the number of burner units 8 in the burner assembly 5, is the azimuth of the Nth burner unit 8 among the NC burner units 8, is the imaginary unit, and the azimuth components have an integer order M in the range [-ceil(NC / 2)+1; floor(NC / 2)], where floor(NC / 2) is the largest integer less than or equal to NC / 2, and ceil(NC / 2) is the smallest integer greater than or equal to NC / 2. The azimuth Figure 2 of the Nth burner unit 8 (see ) is defined as the angle between the reference plane RP 1 (for example, the radial intermediate plane of the reference burner unit 8) and the corresponding plane RPN of the Nth burner unit 8 (for example, the radial intermediate plane of the Nth burner unit 8).

[0072] The azimuth components of order M themselves are pulsation signals and provide further information about the pulsation state of the burner units 8. Thus, the azimuth components of order M can be used to activate protective measures.

[0073] Then the process described in the reference Figure 3 can be applied. In fact, such a process is independent of the specific nature of the pulsation signal used and the specific spectral parameters selected for testing. In other words, the process does not depend on how (e.g., through pressure or optical or other sensors) a specific pulsation signal is generated, and does not depend on whether the pulsation signal represents the pulsation at a single corresponding burner unit 8 (e.g., the independent pulsation signal P N (t)), or is provided as a combination of pulsation signals P N (t) and thus represents the combined effect of pulsations at different burner units 8 (e.g., the azimuth components of order M ). Additionally, the spectral parameters can be the peak amplitude or peak frequency as defined above, and relevant amplitude and frequency thresholds can be used as appropriate to define the range of unacceptable values.Figures 4 - 10 and Figure 12 The spectral parameters of the example of may be the azimuth components of order M The spectral parameters of

[0074] Therefore, after applying the fast Fourier transform, the azimuth components of order M can be extracted The spectral parameters of, and the original time series TSR of the spectral parameters can be established and iteratively updated N . The spectral parameters may include the peak amplitude and / or peak frequency of the spectral peaks in one or more or all of one or more monitoring bands for the azimuth components in any combination, or throughout the spectrum. The original time series TSR can be smoothed, for example, by low-pass filtering N to produce the working time series TSW N , which is then tested to meet the activation criteria defined above. The compliance test includes comparing the values of the working time series TSW of the azimuth components N with the (azimuth) amplitude and / or frequency thresholds and the matching value criteria and / or time criteria. In one embodiment, the processing unit 13 determines all the azimuth components of order M within the range [-ceil(NC / 2)+1; floor(NC / 2)] . In one embodiment, the processing unit 13 determines the combinations of different orders M or all orders M of the azimuth components within the range [-ceil(NC / 2)+1; floor(NC / 2)] , and determines the working time series TSW from the combinations of the azimuth components N .

[0075] In one embodiment, the processing unit 13 determines the azimuth component of order 0, i.e., the in-phase pulsation component P IP (t) defined by the following formula

[0076]

[0077] The in-phase pulsation component P IP (t) is in turn a pulsation signal. The spectral parameters include the in-phase peak amplitude of the in-phase pulsation component P IP (t). The processing unit 13 is configured to update and compare the working time series TSW IP of the in-phase peak amplitude of the in-phase pulsation component P N with the pulsation threshold (in-phase pulsation threshold). The range of non-permissible values includes in-phase pulsation values greater than the pulsation threshold. The known in-phase pulsation component P IP (t) may cause torsional vibration of the rotor 7. Monitoring the in-phase pulsation component P IP ​The spectral parameter of (t) allows activation of protective measures also against torsional vibrations of the rotor, thus preventing torsional vibrations of the rotor.

[0078] refer to Figure 4 and Figure 10 In one embodiment, the spectrum parameters include for each pulsatile signal P N (t) multiple peak amplitudes A in the corresponding programmed frequency band K , and the processing unit 13 is configured to convert the peak amplitude A K Working time series TSW N The combination of and the combined amplitude threshold A 0 As a non-limiting example, the combination may be for each pulsating signal P N (t) peak amplitude A K The linear combination of the values ​​of 1 A 1 +…+k NI A NI , where NI is the pulse signal P N (t) is the number of significant peak amplitudes in the spectrum, and K 1 , ..., K NI is the coefficient of the linear combination. Therefore, for the pulsating signal P N The impermissible range of values ​​of (t) IRVI includes values ​​greater than the combined amplitude threshold A 0 The combined values ​​of:

[0079] IRVI = {k 1 A 1 +…+k NI A NI > A 0}.

[0080] exist Figures 10 - 11 In the example, the two peak amplitudes A 1 , A 2 are considered as spectral parameters. Figure 10 The solid line in FIG. 1 shows an exemplary working time sequence TSW. N . Figure 11 An activation signal ACT for activating the protective measure supplied by the processing unit 13 is shown. N Remaining within the impermissible value range IRVI for more than a first time interval T 1 At a time interval of , the activation signal ACT switches to the activation value.

[0081] refer to Figure 12 In one embodiment, the spectral parameters include the corresponding peak amplitude A 1 At least one peak frequency F 1and the processing unit is further configured to compare the working time series of the peak frequency with a lower frequency threshold FTHL and an upper frequency threshold FTHU. In this example, the inadmissible value range IRVI includes the frequency band delimited by the lower frequency threshold FTHL and the upper frequency threshold FTHU.

[0082] Finally, it is clear that changes and variations can be made to the described and illustrated gas turbine and method without departing from the scope of protection of the appended claims.

[0083] Specifically, it is clear that any combination of the described spectral parameters can be advantageously used and monitored for the purpose of pulsation protection, depending on design preferences.

Claims

1. A gas turbine engine, comprising: a burner assembly (5) having a plurality of burner units (8); and a control system (3) configured to control the air supply and fuel supply to the burner assembly (5); the control system (3) includes: A pulsation sensor (12) is connected to a corresponding burner unit (8) and is configured to provide a pulsation signal (P N (t)) in response to pulsations at the corresponding burner unit (8); and Processing unit (13), which is connected to the pulsation sensor (12) to receive the pulsation signal (P N (t)), and is configured to: Determine at least one spectral parameter (A N (t)) of the pulsation signal (P 1 ; A 1 , A 2 ; F 1 ); the working time series (TSW N ); and Based on the working time series (TSW N ), selectively activate protection measures according to the activation criteria; wherein the activation criteria include a value criterion defined by a non - allowable value range (IRVI) of the spectral parameters (A 1 ; A 1 , A 2 ; F 1 ), and a time criterion based on the persistence of the spectral parameters within the non - allowable value range (IRVI); wherein the spectral parameter includes at least one peak amplitude (A 1 ; A 1 , A 2 ), and the processing unit (13) is further configured to compare a working time series (TSW 1 ; A 1 , A 2 ) of the peak amplitude (A N ) with a corresponding independent amplitude threshold (ATH N ), and the non-permissible value range (IRVI) includes peak amplitude values greater than the independent amplitude threshold (ATH N ); and wherein the spectral parameter includes a respective programmed frequency band (B N (t)) for each of the at least one pulsation signal (P 1 , B 2 ) and a plurality of peak amplitudes (A 1 , A 2 ), and the processing unit (13) is further configured to compare a combination of the working time series (TSW 1 , A 2 ) of the peak amplitudes (A N ) with a combined amplitude threshold (A 0 ), the non-permissible value range (IRVI) including combined values greater than the combined amplitude threshold (A 0 ).

2. The gas turbine engine according to claim 1, wherein, The spectral parameters include at least one peak frequency (F 1 ) corresponding to a respective peak amplitude (A 1 ), and the processing unit (13) is further configured to compare a working time series (TSW 1 ) of the peak frequency (F N ) with a lower frequency threshold (FTHL) and an upper frequency threshold (FTHU), and the non-permissible value range (IRVI) includes a frequency band defined by the lower frequency threshold (FTHL) and the upper frequency threshold (FTHU).

3. The gas turbine engine according to claim 1, wherein, The processing unit (13) is configured to determine the original time series (TRW N (t)) of the spectral parameters (A 1 ; A 1 , A 2 ; F 1 ) from the pulsation signal (P N ), and to determine the working time series (TSW N ) from the corresponding original time series (TRW N ) by low-pass filtering.

4. The gas turbine engine according to claim 1, wherein, the time criterion includes at least one of the following: The spectral parameters (A N ) of the working time series (TSW 1 ; A 1 , A 2 ; F 1 ) continuously remain within the inadmissible value range (IRVI) for at least a first time interval (T 1 ); The spectral parameters (A N ; A 1 ; A 1 ; A 2 ; F 1 ) of the working time series (TSW 2 ) remain within the inadmissible value range (IRVI) continuously or discontinuously within the inspection window (W) for at least a cumulative second time interval (T 2 ); The time counter (TC) reaches the counting threshold (C 0 ), the time counter (TC) being incremented by the processing unit (13) when the spectral parameters (A N ; A 1 ; A 1 ; F 2 ; F 1 ) of the working time series (TSW N ) are within the non-permissible value range (IRVI), and remaining unchanged or being decremented by the processing unit (13) when the spectral parameters of the working time series (TSW N ) are outside the non-permissible value range (IRVI).

5. A method of operating a gas turbine, the gas turbine including a burner assembly (5) having a plurality of burner units (8) and a control system (3), the control system configured to control the air supply and fuel supply to the burner assembly (5); the method includes: Providing a pulsation signal (P N (t)) in response to pulsations at the respective burner unit (8); Determine spectral parameters (A N (t)) of at least one of said pulsating signals (P 1 ; A 1 , A 2 ; F 1 ); a working time series (TSW N ); and Selectively activate protection measures based on the working time series (TSW N ),) and the activation criteria; wherein activating the protection measure includes modifying the air supply and / or fuel supply to the burner assembly (5); wherein the activation criteria include a value criterion defined by a non - allowed value range (IRVI) of the spectral parameters (A 1 ; A 1 , A 2 ; F 1 ), and a time criterion based on the persistence of the spectral parameters within the non - allowed value range (IRVI); wherein the spectral parameter includes at least one peak amplitude (A 1 ; A 1 , A 2 ) in a corresponding frequency band; and further includes comparing a working time series (TSW 1 ; A 1 , A 2 ) of the peak amplitude (A N ) with a corresponding independent amplitude threshold (ATH N ), and the non - allowed value range (IRVI) includes peak amplitude values greater than the independent amplitude threshold (ATH N ); and wherein the spectral parameters include a plurality of peak amplitudes (A N , A 1 , A 2 ) in respective programmed frequency bands for each of the at least one pulsatile signal (P N (t)); and further includes comparing a combination of the working time series (TSW N ) of the peak amplitudes with a combined amplitude threshold (A 0 ), the non - allowable value range (IRVI) including combined values greater than the combined amplitude threshold (A 0 ).

6. The method according to claim 5, wherein, The spectral parameters include at least one peak frequency (F 1 ) of the corresponding peak amplitude; and further include comparing a working time series (TSW 1 ) of the peak frequency (F N ) with a lower frequency threshold (FTHL) and an upper frequency threshold (FTHU), and the non-permissible value range (IRVI) includes a frequency band defined by the lower frequency threshold (FTHL) and the upper frequency threshold (FTHU).

7. The method according to claim 5, wherein, the time criterion includes at least one of the following: The spectral parameters (A N ; A 1 , A 1 , A 2 ; F 1 ) of the working time series (TSW 1 ) continuously remain within the said inadmissible value range (IRVI) for a first time interval (T 1 ); The spectral parameters (A N ; A 1 ; A 1 ; A 2 ; F 1 ) of the working time series (TSW 2 ) remain continuously or discontinuously within the inadmissible value range (IRVI) in the inspection window (W) for at least a cumulative second time interval (T 2 ); The time counter (TC) reaches a count threshold (C 0 ), the counter being incremented by the processing unit (13) when the spectral parameters (A N ; A 1 ; A 1 ; F 2 ; F 1 ) of the working time series (TSW N ) are within the non-permissible value range (IRVI), and remaining unchanged or being decremented by the processing unit (13) when the spectral parameters of the working time series (TSW N ) are outside the non-permissible value range (IRVI).

8. The method according to claim 5, wherein, Determine that the working time series (TSW N ) includes low-pass filtering of the corresponding original time series (TRW N ).

Images