Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
2000-02-05
2002-03-26
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S521000
Reexamination Certificate
active
06362629
ABSTRACT:
TECHNICAL FIELD
The technical field of the invention includes methods and apparatus for monitoring, detecting, indicating, evaluating and signaling electric arcs or sparks.
BACKGROUND
The chaotic electromagnetic emanations manifesting themselves as electric arcs or sparks are closely linked to matter, wherein electromagnetic interactions bind electrons to nuclei in atoms and molecules and wherein the fundamental unit of electromagnetic radiation is the photon.
Indeed, spectra of electric arcs and sparks extend practically from DC through the entire radio-frequency spectrum and through microwave, infrared and light spectra.
Useful exploitations of the electric arc and spark phenomenon include the electric arc lamp, electric welding, the electric-arc-type of metallurgical furnace, the arc type of ion generator in satellite thrusters and for propulsion in outer space, the spark-plug-type of ignition in internal combustion engines, and electric spark ignition in gas appliances.
Unfortunately, the same quality of the electric arc or spark that led to electric lighting, electric arc welding and metallurgy, and ignition of internal combustion, has catastrophic effects in electrical faults that cause explosions or devastating fires through chaotic arcing or sparking.
By way of example, electric arc monitors would be useful in garages, automobile or motorcar repair facilities, gasoline (British “petrol”) storage or dispensing facilities and in other areas where accidental electric arcing can cause disastrous explosions.
Moreover, fuses and circuit breakers are capable of preventing serious overload conditions, but they are generally ineffective to prevent electrical fires and other damage from accidental arcs and sparks which typically generate enough heat for a fire at electric current levels below the level at which the fuse will blow or the circuit breaker will trip. Reliable arc monitoring would thus be highly desirable in a large number and variety of electrical circuits.
These are, of course, only representative examples of fields where reliable arc or spark monitoring could be useful.
A major stagnating problem in this respect has been that prior-art development has run its course in its fear of false alarms. Of course, false alarms are the bane of alarm systems, as frequent occurrence of false alarms can nullify the utility of any alarm system.
Accordingly, in an effort to reduce the possibility of false alarms arising from radio broadcast and radio frequency security system signals, the arc detection system as disclosed in the International Patent Publication WO090/04278, by HAMPSHIRE, Michael John, rejects frequencies below about 160 kHz and above some 180 kHz of the arc signal signature, leaving for electrical fault detection only a narrow 20 kHz band at some 170 kHz center frequency. This, however, left a sample for arc detection that was dozens of times too small in the 100 kHz range for reliably detecting the occurrence of an arc signature while at the same time preventing the occurrence of false alarms equally reliably.
An arc detection system which avoids that drawback is apparent from PCT/US90/06113, filed Oct. 24, 1990 and published as W
0
92/08143, by Hendry Mechanical Works, inventors HAM, Jr., Howard M., and KEENAN, James J., and in its corresponding U.S. Pat. No. 5,373,241, issued Dec. 13, 1994, and U.S. Pat. No. 5,477,150, issued Dec. 19, 1995, all herewith incorporated by reference herein for the United States of America and for all other countries where incorporation by reference is permitted. Reference should also be had to their corresponding EPO 507 782 (90917578.8) and resulting European national patents, and to their corresponding Australian Patent 656128, Canadian Patent Application 2,093,420, Chinese Patent Application 92102453.3, Japanese Patent Application 500428/91, Korean Patent Application (PCT) 701219/93, and Mexican Patent 178914 (9201530), all herewith incorporated by reference herein for all countries where incorporation by reference is permitted. That system avoids false alarms by converting instantaneous arc signature frequencies into a combination frequency from which arc-indicative signals are detected in contradistinction to extraneous narrow-band signals that could cause false alarms.
Against this background, a frequency selective arc detection system of a subsequently filed prior-art application, appears as a typical representative of the prior-art approach to arc detection. It accordingly presents a variety of approaches to arc detection that mainly look at frequencies in the upper kilohertz range, such as from 100 kHz to one megahertz. This, however, covers not only major portions of the public A.M. radio broadcast band, also known as “long-wave” and “medium-wave” broadcast bands in some countries, but also the kind of control or security systems radio frequency band referred to in the above mentioned W
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90/04278 reference. Depending on location, one thus had to contend with dozens of extraneous signal interferences.
The same in essence applies to another embodiment in that prior-art proposal that suggests using a comb filter arrangement composed of four bandpass filters each of which has a 50 kHz passband, and three of which have a center frequency of 225 kHz , 525 kHz, and 825 kHz, respectively. In the A.M. broadcast and above mentioned control and security systems radio frequency band portion of that spectrum, 50 kHz samples can only represent minor fragments of the chaotic arc signature, raising the danger of false alarms from coincidental extraneous signals. This also affects the efficacy of the 55 kHz bandpass filter in that comb filter arrangement, inasmuch as that prior-art proposal continuously rotates its detection process among the four filter components of that comb filter arrangement.
A prior effort at arc detection that ventured into low frequency regions effected monitoring in various low frequency bands that were too narrow for reliable arc detection as apparent from articles by B. D. Russell et al., entitled “An Arcing Fault Detection Technique Using Low Frequency Current Components—Performance Evaluation Using Recorded Field Data” and “Behaviour of Low Frequency Spectra During Arcing Fault and Switching Events” (IEEE Transactions on Power Delivery, Vol. 3, No. 4, October 1988, pp. 1485-1500) indicating lack of success.
These developments in retrospect appear largely as a reaction to the perception of electric arcs as highly random phenomena borne out of the chaotic nature of arc signatures. This prior-art perception, however, ignores the fact that chaotic systems have a deterministic quality, and can be successfully dealt with, if one is able to discover what the underlying principles are and how they can be put to effective use.
Indeed, even chaotic electric lightning displays some self-similarity among its arboresque nocturnal discharges and within the branched configuration of its lightning bolts.
In this respect, pioneering work done by Benjamin Franklin and by Georg Christoph Lichtenberg back in the 18th Century casts a long shadow all the way to the subject invention.
In particular, Franklin through his famous kite experiment in a thunderstorm proved that lightning is an electrical phenomenon. Lichtenberg thereafter created his famous “Lichtenberg figures” in 1777 by dusting fine powder, such as sulfur, over insulating surfaces over which electrical discharges had taken place. Many of these Lichtenberg figures of electrical discharge resemble lightning in appearance and otherwise display a striking self-similarity in their patterns of branching lines and within such branching lines themselves. Manfred Schroeder compared this to diffusion-limited aggregation (DLA) in his book entitled “FRACTALS, CHAOS, POWER LAWS” (W. H. Freeman and Company, 1991), pp. 196, 197, 215 and 216. Kenneth Falconer, in his book entitled “FRACTAL GEOMETRY” (John Wiley & Sons, 1990), pp. 270 to 273, also applied the DLA model to electrical discharges in gas.
By way of background, fractals are phenomena in the fractal geometry conceived,
Benoit Luc Pierre
Ham Margaret F.
Ham, Jr. Howard M.
Keenan James J.
Parker Michael T.
Ham Margaret F.
Hendry Mechanical Works
Koppel & Jacobs
Metjahic Safet
Nguyen Vincent Q.
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