Thermal measuring and testing – Temperature measurement – Nonelectrical – nonmagnetic – or nonmechanical temperature...
Reexamination Certificate
2000-11-07
2003-02-04
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
Nonelectrical, nonmagnetic, or nonmechanical temperature...
C374S152000
Reexamination Certificate
active
06513972
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to multiple-component electrical systems such as those used in the power generation industry and, more particularly, to the field of monitoring conditions of electrical generator systems.
BACKGROUND OF THE INVENTION
In the power generation industry, monitoring the conditions of components of electrical generator systems is essential for the efficient and nonhazardous functioning of such systems. Effective monitoring encompasses detecting and registering conditions in various components including generators, exciters, collectors and large utility transformers. Conventional techniques for monitoring the temperature of such components use thermocouples or resistance temperature detector devices which convey temperature information with conductors. Such devices and techniques, however, are limited and have significant drawbacks. For example, the devices cannot be routed across components operating at high voltage nor where there is a risk of flash-over or electromotive force (emf) distortion. The ability to measure accurately the temperature of a component is thus further limited because temperature measuring devices cannot be positioned in proximity to critical areas whose temperatures it is desirable to monitor. Therefore, critical areas cannot be well-monitored using these conventional devices and methods.
These limitations on monitoring the condition of power generator systems, moreover, often necessitate monitoring by visual means, which, in turn, may require shutting down a system and imposing costs associated with the downtime of the system while visual inspections are performed. Moreover, because visual monitoring can only be undertaken at intermittent intervals, there is no capability for continuous monitoring of electrical system components. Thus, such conventional techniques and devices suffer deficiencies in terms of both efficiency and efficacy. Conventional techniques are more costly whenever monitoring requires suspending system operations. They also are inevitably less reliable when they can not monitor each component's temperature accurately or can not measure temperature continuously throughout the system.
Other devices and methods have been tried for certain types of components, but these are also subject to limitations and constraints on efficiency and efficacy. For example, U.S. Pat. No. 4,818,975 by Jenkins titled “Generator Stator Core Temperature Monitor” proposes measuring ambient temperature of the stator core of a generator in terms of hydrogen gas (H
2
) exiting through the stator core. Temperature of the core can be inferred from either of two effects: (1) the hotter the gas, the more frequent the gas molecules impinge on a temperature-responsive liquid crystal so as to block monitored light; and (2) the hotter the gas, the greater the expansion of a housing-mounted flexible bladder thereby influencing the angle and hence amount of light detected. There are at least two limitations with this type of monitoring, however. First, owing to the relative diffusion of gas molecules, gas is a less efficient heat conductor. Accordingly, the hydrogen gas is a less efficient, less reliable conveyor of temperature information. Second, and more fundamentally, this type of monitoring measures only an aggregate or average temperature of the environment surrounding the stator, not the actual temperature of a specific system component. This can be especially limiting given the need to detect and isolate a temperature variation occurring in individual components. Measuring ambient temperature does not permit separate monitoring and detecting of temperature variations in individual components. Detection, moreover, is also delayed until, for example, an overheating condition in a single component contributes sufficient heat to raise the average or ambient temperature surrounding the stator or other electrical system.
U.S. Pat. No. 4,203,326, by Gottlieb et al. titled “Method and Means for Improved Optical Temperature Sensor” proposes an “optical conductor” to measure temperature, but does not address directly the problems of the more conventional type conductor temperature information conveyors. Such devices combine an optical core with cladding, along with a jacket to encase the core and clad material. The core and clad material are formed so as to produce a temperature-influenced difference in refractive indexes that is intended to overcome a common problem with such conductors: temperature responsiveness varies linearly with the length of the conductor. But whatever deficiencies may be corrected with respect to this conductor-length factor, such a device registers only a temperature range and does not address other problems described above. Moreover, there are additional limitations inherent in such devices that limit the efficiency with which temperature detection can be performed. For example, thermal disruption of the fiber conductor by melting in the fiber or surrounding cladding disturbs light conduction. Although using different cladding material can compensate for this risk, doing so can further complicate choosing a proper material composition that will provide the correct refractive indexes difference to accurately monitor for temperature variation. Finally, in addition to their above-described complications in achieving a desired result, such devices also are fundamentally limited in the result that is achieved. Specifically, such devices provide detection of only a range of temperatures, thereby providing less-than-desirable accuracy and problematic delay in monitoring for critical conditions like overheating in an electrical system component.
There is thus a critical need for an apparatus or method that overcomes the problems inherent in conventional and optical conductor type devices for monitoring electrical generator components. Specifically, there is the need for a device or method that more accurately and more efficiently measures the temperatures of the distinct components of a power generator system, as well as the ambient temperature of the system at various locations.
SUMMARY OF THE INVENTION
In view of the foregoing background, the present invention advantageously provides an apparatus and method for efficiently and efficaciously monitoring the temperature of one or more regions or components of a multiple-component system, such as a power generator system wherein one confronts such inhibiting factors as high voltage and flash-over risk. The present invention advantageously provides a more accurate capability for monitoring temperature and detecting temperature variation in electrical system components. Moreover, although the apparatus and method are described herein in the context of electrical generator systems, they can have wide applicability in other contexts as will be apparent to one skilled in the art. Such uses include monitoring air conditioning systems and other building service devices whose temperatures need to be monitored effectively and efficiently on a substantially continuous basis. Specifically, as described herein, vital temperature information using the apparatus and method of the present invention is directed efficiently and rapidly to a temperature variation monitor so as to monitor critical temperature variations in a direct, efficient, and reliable manner.
Further advantage is provided in that critical temperature information can be conveyed from within the system to a remote site. This provides capabilities for safe, continuous temperature monitoring using the apparatus and method of the present invention. Notwithstanding this significant advantage, the present invention can be used just as effectively for direct local monitoring of a system component's temperature.
The present invention, moreover, specifically provides the capability of strategically positioning a plurality of temperature monitoring devices or “temperature probes” within any number of selected critical areas within an electrical generator system. Moreover, the present invention allows these temp
Gutierrez Diego
Siemens Westinghouse Power Corporation
Verbitsky Gail
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