Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Instruments and devices for fault testing
Reexamination Certificate
2000-11-28
2002-11-26
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Instruments and devices for fault testing
C073S570000
Reexamination Certificate
active
06486678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to testing methods for evaluation the operation of mechanical devices through acoustical recording and analysis.
2. Background Information
Maintenance of an electrical distribution system is extraordinarily expensive for utilities, and failures in such a system can be equally, if not more expensive, in the aggregate for utility customers (loss of computer data, food spoilage, work interruptions, loss of ability to transact with customers, etc.). It is clear, then, that preventative maintenance, if feasible, is highly desirable. However, presently known and implemented technology and methods do not economically allow the preemptive detection of problems which account for the majority of power interruptions in an electricity distribution system.
Over 80% of all power interruptions in an electrical power distribution system are caused at the power substation level (as opposed to downed peripheral lines and lightening strikes, for example). Of the substation malfunctions which cause power interruptions, over 40% are caused by malfunctioning mechanical electrical power system components. At present, power companies seldom know of a malfunctioning switch, breaker, load tap charger (“LTC”), or motor until it fails and a real power interruption has already occurred. Present skill and methods in the field do not provide reliable means of otherwise detecting a malfunctioning, or soon-to-be malfunctioning mechanical components, other than tearing them down for physical inspection—a cost prohibitive approach to preventative maintenance. A few non-invasive testing methods are known or proposed (ultrasound imaging, for example), but these are not proven, and have very limited application in terms of the components with which they are even arguably useful.
It would well serve utilities and their customers, to a degree which is, perhaps, impossible to fully value, to provide some means by which the utilities could detect sources of likely substation-level malfunctions of mechanical components in an electrical power system (switches, breakers, LTCs and motors) before they occur in order to minimize the incidences of actual power interruptions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a non-destructive testing and evaluation method by which damaged or malfunctioning mechanical components in an electrical power system in an electrical distribution system may be detected in a cost effective and easily carried out method.
It is another object of the present invention to provide a method by which preventative maintenance of mechanical components in an electrical power distribution system may be cost effectively carried out on appropriately targeted units, identified through non-destructive, simple analysis.
It is another object of the present invention to provide a novel and cost effective method for identifying mechanical components in an electrical power distribution system which are likely to require imminent repair to prevent failure.
In satisfaction of these and related objects, the present invention provides a remarkably simple and cost effective method by which operating mechanical components of an electrical power distribution system may be evaluated to determine whether or not they exhibit operational characteristics which indicate sub-standard performance or imminent mechanical failure. The present method is based on the fact that mechanical devices produce a mix of sound comprised of the individual sounds generated by the actions of various components associated with their operations.
Properly operating machines will produce “signatures” which are apparent from the measuring and depicting (graphically in most cases) of such parameters as decibel production over time (relative amplitude expressed in dB), sound production in terms of frequency over time, and relative amplitude sound at different frequencies over time. A mechanical device which is malfunctioning to a greater than nominal degree will produce such signatures as are recognizably, and, in most cases, perceptively different through mere visual examination and comparison with normal signatures. Even when reference signatures of properly operating mechanical devices are not available, a familiarity with devices in certain families of such devices will often allow an experienced technician to recognize likely malfunctioning components (as has been discovered by the present inventor in his work with electrical power system equipment).
Initial testing and evaluation of the present method has proven remarkably reliable in detecting problems with electrical distribution system switches, breakers, LTC and motors—problems for detecting which a physical tear down was the only clearly reliable alternative. In every case during tests of the present method (several dozen instances) in which the present inventor has identified a suspect breaker or switching unit through practice of the present invention, physical inspection by the utility revealed conditions which unarguably would have soon resulted in failure of the unit and an actual power interruption in the grid.
If implemented on a nationwide basis, the present method can save utilities millions of dollars by avoiding the more costly repairs as attend a total failure of a unit, and by avoiding needless intervention in units which may be deemed “healthy” through use of the method. The savings to utility customers for lack of actual power interruptions will be substantial as well, not to mention the enhanced, over-all safety arising from fewer power losses to medical facilities, traffic lights, etc.
REFERENCES:
patent: 4480480 (1984-11-01), Scott et al.
patent: 4707687 (1987-11-01), Thomas et al.
patent: 5566092 (1996-10-01), Wang et al.
patent: 5852793 (1998-12-01), Board et al.
patent: 5995910 (1999-11-01), Discenzo
Henry David G.
Le N.
Spears Paul
Sundaram T. R.
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