Data processing: structural design – modeling – simulation – and em – Simulating nonelectrical device or system – Mechanical
Reexamination Certificate
1998-01-14
2001-03-27
Teska, Kevin J. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Simulating nonelectrical device or system
Mechanical
C703S002000, C702S034000, C702S035000
Reexamination Certificate
active
06208953
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for monitoring plants with mechanical, in particular hydromechanical, components.
2. Description of the Prior Art
For industrial applications, for example, for the generation of electrical energy, complex plants which comprise a large number of components are often used. As a representative example reference is made in the following to a hydroelectric power plant in which turbines are driven by means of hydraulic force for the generation of electrical energy. In this example, the hydromechanical components are thus the turbines, which are set rotating by flowing water and which drive the generators.
From the points of view of safety and economy, it is very important to continuously monitor such plants and their components during operation in order to detect disturbances in the operation, that is, deviations from normal operating behavior, as early and reliably as possible. Often a plurality of parameters such as, for example, pressure, temperatures of the water at different positions in the plant, flow rates, speeds of rotation, powers, bearing temperatures etc., are determined by measurement and e.g., stored and/or graphically displayed as a function of time. Usually, however, components such as turbines do not operate at a fixed operating or working point, so that the temporal behavior of the measured values to be determined for monitoring exhibits pronounced fluctuations even in normal, that is, disturbance-free operation. Therefore, it is very difficult to judge on the basis of the temporal behavior of the measured values—if at all—whether the plant is operating correctly, free of disturbance. In addition, it is difficult to detect and to judge very slow temporal variations such as arise, for example, through operational wear.
In principle, it would indeed be possible to model the entire plant physically, that is, to calculate the physical relationships between the individual parameters, and then to perform an assessment of the operating state through a comparison between such physical model calculations and the values determined by measurement. In practice, however, this way is frequently too cost-intensive and laborious so that it is poorly suited for industrial applications in particular. One reason for this is that industrial plants have an enormous complexity with numerous components in mutual interaction so that a moderately reliable physical model must take a large number of relationships between the individual parameters into account, through which its generation becomes an extremely difficult, time consuming and cost-intensive task.
Therefore, it is customary in practice for the monitoring of the plant, in particular, for industrial applications, to predetermine fixed threshold values for several selected parameters, for example, the temperature in the bearing of a rotating shaft or the temperature of a coolant, on exceeding which an alarm is triggered or a warning is issued. This kind of monitoring has disadvantages however. There is namely the danger that operational disturbances or faults actually existent in the plant are overlooked or detected too late. Thus, it is possible, for example, that a bearing of a shaft or a seal has a defect, but that the monitored temperature does not exceed the threshold value required for triggering the alarm because the turbine is momentarily operating only at a low load. On the other hand, it is possible for false alarms to be triggered, for example, when the turbine briefly operates at a very high load, so that the threshold value required for triggering the alarm is exceeded with out a defect being present. A false alarm of this kind can lead to the plant being switched off without it actually being necessary, which is very disadvantageous, in particular, from the economic point of view.
SUMMARY OF THE INVENTION
Starting from this state of the art it is thus an object of the invention to provide a method for monitoring plants with mechanical, in particular hydromechanical, components which does not have the disadvantages mentioned. The method should enable a reliable and early detection of operation disturbances and be suitable for industrial applications. The method should, in particular, be suitable for the monitoring of those plants and/or components which are operated at variable working points. The method should also permit a simple assessment of the operating state of the components. It should furthermore be possible with this method to detect temporally slowly progressing changes, such as e.g., are caused by wear. In addition, the method should enable trends for the further operation of the components to be recognized.
The method for monitoring plants with mechanical, in particular hydromechanical, components which can be operated at variable operating point s satisfying this object is characterized by the features of the independent claim. The method in accordance with the invention thus comprises the following steps:
During the operation of the components, measured values are determined at predeterminable time intervals for a fixed set of parameters. The measured values which are determined for various working points during a modelling phase are used for the generation of a model for the operating behavior of the components, with the input variables of the model being at least a portion of the set of parameters and with the output values comprising a model value for at least one of the parameters. A residue is formed in each case by comparison of the respective model value with the corresponding actual measured value of the modelling phase. The model is optimized by the determination of model parameters in such a manner that a modelling error which can be derived from the residues is a minimum. With the help of this model for the operating behavior at least one monitoring value which is independent of the respective current working point is derived at predeterminable intervals. The temporal behavior of the monitoring value is used for estimating the wear in the components and/or for the detection of operating disturbances.
Since the model for the operating behavior is generated and optimized on the basis of experimentally determined measured values which are determined during the operation of the unit, elaborate and difficult determinations of the physical relationships between the individual parameters are not necessary, so that the method in accordance with the invention is suitable for industrial uses in particular.
The method in accordance with the invention makes use of a monitoring variable which is independent of the respective current operating point, which means that fluctuations in the measured values for the parameters which are based merely on changes in the operating point do not lead to significant changes in the monitoring variable. The method thus takes into account the mutual influence between the parameters at varying working points. In other words, this means that the monitoring method in accordance with the invention does not operate with fixed threshold values for definite parameters, but rather that the threshold values are adapted to the respective current operating state. This permits a very reliable and early detection both of operating disturbances and of slowly progressing changes such as are caused, for example, by wear. The triggering of false alarms and the “overlooking” of operating disturbances, e.g. in operation at partial load, practically no longer arises in the method in accordance with the invention. This is advantageous, in particular, from the point of view of economy and safety. Through the reliable monitoring, unnecessary standstill times of the plant can be avoided and the maintenance costs significantly reduced.
Since the monitoring variable is independent of the respective current working point, a substantially temporally constant value results for it as long as the plant and/or the components are operating without defect and wear. As soon as a change in the component caused by defect
Guettinger Heinz
Milek Janusz
Sergent Douglas W.
Sulzer Innotec AG
Teska Kevin J.
Townsend and Townsend / and Crew LLP
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