Abstract:
A degradation monitoring system including: a machine; a sensor affixed to the machine, the sensors measuring a operational parameters of the machine; a set of filters receptive of information about the machine from the sensors and the filters responsively generate status signals; and comparators for comparing the status signals to stored signals, wherein the comparators indicate at least one of a presence of degradation of the machine, or a cause of degradation of the machine.

Description:
BACKGROUND  
       [0001]     This disclosure relates generally to a system and method for monitoring turbine degradation. Specifically, this disclosure relates to an automated system and method for monitoring steam turbine degradation.  
         [0002]     Turbines suffer performance degradation over time from various sources such as solid particle erosion, deposit buildup, foreign object damage, and increased clearances due to rubs, etc. Currently, when the performance of the turbine reaches unacceptably low values, the turbine is opened to evaluate the extent and nature of the degradation and to perform corrective maintenance work to improve the condition of the turbine. Prior knowledge of the turbine health is important for planning maintenance work, scheduling outages, and ordering parts in advance of maintenance in order to minimize outage time.  
         [0003]     Detailed steam turbine performance information is typically obtained through performance evaluations tests (PETs), which are performed either at the turbine installation or before and after an outage. In between PETs, performance is usually monitored using offline trending data from sensors in the steam turbine. This trending information is analyzed using a set of heuristic rules to decide possible causes for a given degradation. Expert engineers, who need to account for external effects that may confound the degradation in the trending data, are required to analyze the trending data.  
         [0004]     The assessment of steam turbine performance degradation has always been important to maintaining operating margins in the power generation business, and it is becoming increasingly critical for satisfying contractual guarantees on performance, output, and availability. Current approaches to steam turbine health monitoring and diagnostics rely almost entirely on heuristic algorithms. This approach is prone to errors, due to lack of appropriate expert knowledge, incomplete sensor data, and changing system characteristics.  
       BRIEF DESCRIPTION  
       [0005]     Disclosed herein is a turbine degradation monitoring system including: a turbine; a sensor affixed to the turbine, the sensor measuring an operational parameter of the turbine; a processor receptive of information about the turbine from the sensor and the processor responsively generates a status signal; and a comparator for comparing the status signal to a stored signal, wherein the comparator indicates at least one of a presence of degradation of the turbine, or a cause of degradation of the turbine.  
         [0006]     Also disclosed herein is a method for monitoring turbine degradation including: developing a physics-based model of a turbine, wherein the physics-based model includes a stored signal; monitoring an operational parameter of the turbine with a sensor; processing the operational parameters received from the sensor, wherein the processing generates an status signal; and comparing the status signal and the stored signal to detect at least one of a presence of degradation of the turbine, or a cause of degradation of the turbine.  
         [0007]     Further disclosed herein is a system for monitoring turbine degradation including: means for developing a physics-based model of a turbine, wherein the physics-based model includes a stored signal; means for monitoring an operational parameter of the turbine; means for generating a status signal responsive to the operational parameter of the turbine; and means for comparing the status signal and the stored signal to detect at least one of a presence of degradation of the turbine, or a cause of degradation of the turbine.  
         [0008]     Other systems, methods, and/or computer program products according to exemplary embodiments will be or become apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that all such additional systems, methods, and/or computer program products be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying figures, wherein:  
         [0010]      FIG. 1  depicts an exemplary embodiment of a turbine degradation monitoring system; and  
         [0011]      FIG. 2  depicts a flow chart of a method for monitoring turbine degradation. 
     
    
     DETAILED DESCRIPTION  
       [0012]     Referring to  FIG. 1 , a turbine degradation monitoring system is generally depicted at  10 . The turbine degradation monitoring system  10  includes a turbine  12  and sensors  14 , which are capable of measuring operational parameters of the turbine  12 . The operational parameters to be measured may be, but are not limited to, a pressure in the turbine  12 , a temperature in the turbine  12 , a steam flow through the turbine  12 , metal temperatures of components of the turbine  12 , steam valve position, steam quality and may also be a combination of these or a combination including one of the foregoing. The turbine degradation monitoring system  10  also includes filters  16  that receive information about the operation of the turbine  12  from sensor  14  and responsively generates a status signal  18 . The status signal  18  is presented to a comparator  20 , which compares the status signal  18  to a stored signal to detect the presence of degradation in the turbine  12  as well as the source of the degradation. The stored signal may be either a threshold value  22 , a minimum value that is indicative of degradation in the turbine  12 , or a degradation signature signal  24 , a signal indicative of the response of the processor  16  to a specific type of degradation in the turbine  12 . The turbine degradation monitoring system  10  may generate the stored signal by using a model of the turbine  12 .  
         [0013]     The turbine degradation monitoring system  10  requires the development of a model of the physics of the steam flows in the turbine  12  and of the effects of physical parameters responsible for the degradation of the steam path. More specifically, a physics-based model that describes the internal energy and mass balances for a healthy turbine  12  is required for the generation of the threshold value  22 . Additionally, a separate physics-based model is required that corresponds to each type of degradation considered, such as solid particle erosion, deposit buildup, foreign object damage, and increased clearances due to rubs, etc. These models, referred to as typical degradation models, each generate a degradation signature signal  24  indicative of degradation parameters for the specific degradation type.  
         [0014]     In an exemplary embodiment, the filters  16  are presented with information from the sensors  14  and responsively adjust the status signals  18 . The turbine degradation monitoring system  10  includes one filter  16  for each type of degradation of the turbine  12  that is considered. The filter  16  provides an estimate of the state of the turbine  12  and supports estimations of past, present, and even future states of the turbine  12 . The response of each filter  16  to information from given sensors  14  may be different since each filter  16  may be configured to detect different forms of degradation. The turbine degradation monitoring system  10  uses the response of each filter  16  to typical forms of degradation as a basis to determine the nature of an unknown source of degradation. Specifically, the information from sensors  14  in operable communication with the turbine  12  that includes a known type of degradation is presented to every filter  16  and the response of each filter  16  is recorded for different values of the degradation parameters. The filter  16  response for typical degradation types is referred to as the degradation signature signal  24 . All of the degradation signature signals  24  are used to create a database of degradation signature signals  24 , which will be accessed during the operation of the turbine degradation monitoring system  10 .  
         [0015]     In a particular exemplary embodiment, the filters  16  used by the turbine degradation monitoring system  10  includes a Kalman-type filter. The use of the Kalman-type filter allows for an optimal handling of tradeoffs between sensor  14  noises and modeling uncertainty, which results in an optimal filtering of the information received from sensors  14  to provide a fast and accurate response from the filter  16 . Generally, the use of filters  16  including physics-based models (for healthy turbines and for turbines with faults) allows filtering out confounding effects in the information from the sensors  14 , like changes in the operating point of the turbine  12 . For example, changes in the steam flow due to changes in the HRSG or condenser operation may be automatically removed from the analysis.  
         [0016]     Referring now to  FIG. 2 , a flow chart of a method for monitoring turbine degradation is generally depicted at  30 . The first step in the method for monitoring turbine degradation  30 , shown at step  32 , is the development of physics-based models that describe the internal energy and mass balances for healthy turbines and for turbines that include each type of degradation to be considered. These models are developed by collecting and storing information from sensors  14  which are monitoring turbines that are known to be healthy or to have a specific type of degradation. The next step in the method for monitoring turbine degradation  30 , shown at step  34 , is to determine the stored signals from the physics-based models. Specifically, the information from the healthy turbine is used to generate the threshold value  22 , which is a minimum value indicative of a healthy turbine, and the information from the turbines that include specific types of degradation is used to create a database of the degradation signature signals  24 , which are indicative of the operation of a turbine  12  that suffers from a specific type of degradation. The next step in the method for monitoring turbine degradation  30 , shown at step  36 , is to present information from the sensor  14  about the turbine  12  to the processors  16  (one processor  16  for each type of degradation to be considered). At step  38 , the filters  16  generate the status signals  18  responsive to the information received from the sensors  14 .  
         [0017]     Continuing with  FIG. 2 , as shown at step  40 , the method for monitoring turbine degradation  30  detects the presence of degradation using the magnitude of the status signal  18 : if the status signal  18  is less than the threshold value  22  then no degradation is present; otherwise, the method for monitoring turbine degradation  30  declares the presence of degradation. If degradation is detected then the method for monitoring turbine degradation  30  classifies the degradation as an instance of a standard degradation mechanism or declares that root cause of degradation is not recognized by comparing the status signals  18  to the degradation signature signals  24 , as shown at step  42 . Quantitative information on the severity of the degradation may be obtained from the status signal  18  provided by the processor  16  corresponding to the chosen degradation cause. On the other hand, if no degradation is detected, the method for monitoring turbine degradation  30 , at step  44 , indicates that the turbine  12  is healthy.  
         [0018]     The method for monitoring turbine degradation relies on sensor measurements, on system models that represent each type of degradation under consideration, and on an algorithm that calculates models parameters quantitative and qualitative information on the fault or degradation. In an exemplary embodiment, the algorithms that calculate degradation parameters are Kalman filters. Kalman filtering is a mature technology based on measurements and models, typically used to estimate states or parameters that may not be directly measured. In a exemplary application such as turbine degradation estimation, Kalman filters use measurements of steam temperatures, pressures and flows, and physical models of the turbine to continuously calculate the most probable set of parameters for erosion or deposit degradations that may originate the current measurements. Kalman filter technology is applicable when the system models are linear. In case the models are non linear, various other similar techniques for non linear systems may be used. For example, a suitable algorithm for turbine degradation estimation is the extension of Kalman filter techniques for nonlinear systems, known as Extended Kalman Filters (EKF).  
         [0019]     The use of Kalman filter techniques to estimate turbine degradation parameters in different degradation scenarios, like changes in steam path geometry for erosion and/or deposits degradation. As a result of the filter calculations, values of steam magnitudes (pressures, temperatures or flows) for different degradation scenarios are available in real time to improve the diagnosis capabilities. The mismatch between these magnitudes and the corresponding sensor measurements are denoted by status signals and are used to diagnose the turbine degradation.  
         [0020]     The method for monitoring turbine degradation  30  provides information about the turbine  12  as described above in real time for use in plant monitoring and outage planning/scheduling. Additionally, the method for monitoring turbine degradation  30  does not require the presence of an expert to diagnose performance problems from information received from the sensors  14 . The method for monitoring turbine degradation  30  produces performance diagnosis information all the time, making this information available to an operation expert if further analysis is required.  
         [0021]     By continuously estimating turbine degradation, the method for monitoring turbine degradation  30  can fill in the gaps in the knowledge of the state of the turbine  12  between manual inspections, potentially allowing the elimination of unnecessary and expensive manual inspections in the future. Additionally, the method for monitoring turbine degradation  30  provides an automated, model-based steam degradation and trending system to provide assistance to the above-mentioned manual process by detecting and pinpointing changes in turbine health on a continuous basis, rather than at periodic intervals, as is done today.  
         [0022]     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.