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Publication numberUSH536 H
Publication typeGrant
Application numberUS 06/886,995
Publication dateOct 4, 1988
Filing dateJul 18, 1986
Priority dateJul 18, 1986
Publication number06886995, 886995, US H536 H, US H536H, US-H-H536, USH536 H, USH536H
InventorsBrian R. Strickland, George R. Edlin, Calvin C. Easterbrook, Thomas G. Roberts
Original AssigneeThe United States Of America As Represented By The Secretary Of The Army
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of detecting and locating an electrostatic discharge event
US H536 H
Abstract
A method of locating an electrostatic discharge event in a predetermined ucture by sensing electromagnetically that an electrostatic discharge event has occurred and producing a trigger signal from the electromagnetic sensing to control a recording device for the starting of time, utilizing a plurality of acoustic detectors about the structure for sensing the acoustic of the electrostatic discharge event, determining the time elapsed between the starting of time by the electromagnetic sensing and the signals sensed by the acoustic detectors and utilizing the information gained from the times sensed and the predetermined locations of the sensors to determine the location of the electrostatic discharge event in the predetermined structure.
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Claims(4)
We claim:
1. A method of locating an electrostatic discharge event in a predetermined structure, said method comprising sensing electromagnetically that an electrostatic discharge event has occurred, producing a trigger signal from said sensed electromagnetic discharge event and utilizing said trigger signal to control a recording device and start the counting of time at t=0, sensing acoustics from said electrostatic discharge event at three spaced apart positions on said structure and communicating the sensed acoustics as inputs to said recording device to determine the time ellapsed from t=0 until the acoustics from the electrostatic discharge event reaches each of the three sensing acoustic and utilizing the information gained by the electromagnetic sensing and the acoustic sensing to determine the location of the electrostatic discharge event in said structure.
2. A method of locating an electrostatic discharge event as set forth in claim 1, wherein an antenna is used in the electromagnetic sensing of said electrostatic charge event, and wherein high frequency microphones with frequency response from 2.5 KHz to 35 KHz are used for said acoustic sensing.
3. A method of locating an electrostatic discharge event as set forth in claim 2, wherein said recording device utilized is an oscilloscope.
4. A method of locating an electrostatic discharge event as set forth in claim 3, wherein said acoustic sensing is sensed at random positions about said structure.
Description
DEDICATORY CLAUSE

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalties thereon.

BACKGROUND OF THE INVENTION

In the past, it has not been possible to accurately locate electrostatic discharges even though it is important to accurately locate the site of electrostatic discharges that occur in systems or materials that are sensitive to electrostatic discharges. Sensitive electrostatic discharges that need to be identified involve systems that include missile systems that can be damaged by electrostatic discharges and propellants that can be inadvertently detonated by an electrostatic discharge event. These events are electrostatic arcs that are caused by charge separations. The charges may become separated by friction, propellant separation, or by induction fields in voids. These events generally occur subsurface and are not detectable optically. The fact that an event has occurred can be detected electrically, but to locate it electrically requires a very dense grid of sensors which is cost prohibitive, difficult to use and perturb the charge distribution to be monitored. Thus, it can be readily appreciated that a need exists for a relatively inexpensive, easy to use, and accurate way to detect and locate electrostatic discharge events.

Therefore, it is an object of this invention to supply a method by which an electrostatic discharge event can be detected and located.

Another object of this invention is to utilize an electromagnetic method for detecting the event and an acoustic method for producing information from which the site of the electrostatic discharge can be located.

Still another object of this invention is to provide a method that utilizes means that are readily available, relatively simple, relatively inexpensive and have the ability to provide sufficient information to accurately locate an electrostatic discharge event.

Other objects and advantages of this invention will be obvious to those skilled in this art.

SUMMARY OF THE INVENTION

In accordance with this invention, a method of detecting and locating an electrostatic discharge event is provided in which an electromagnetic detector on the structure of the device that has the electrostatic discharge event occuring there at is utilized for detecting that the event has occurred to start the counting of time, three acoustic detectors placed at different positions on the device in which the electrostatic discharge event occurs are utilized for detecting when the acoustic from the electrostatic discharge event reaches each of the acoustic detectors, and determining the time it takes the acoustics to travel to each of the acoustic detectors with the known positions of the acoustic detectors and utilizing this information to determine the location of the electrostatic discharge event within the device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electrostatic discharge detector and locator system for carrying out the method; and

FIG. 2 is a schematic circuit diagram for the system used in the method and illustrating the records caused to be produced by the detectors.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, the event desired to be detected is located in a device such as structure 10 that contains materials that are sensitive to electrostatic discharge. Structures of this type are propellants as well as other types of missile systems. An electromagnetic pickup device 12 is secured in a conventional manner to structure 10 and has an antenna 14 (see FIG. 2) such as a loop or stub antenna for picking up the electromagnetic waves of the event. Antenna 14 is connected by leads 16 through a high frequency audio amplifier means 18 greater than 100 Khz. Amplifier 18 is connected by appropriate lead 20 to a recording device 22 such as an oscilloscope, oscillograph, or computer to provide a trigger input through lead 20 to recording device 22 to mark the starting of time at t=0 as indicated. Even though one electromagnetic pickup device has been illustrated, it may be desirable in some applications to provide more than one electromagnetic pickup on the structure in which the electromagnetic discharge event is to occur. Structure 10 also includes three acoustic detectors 24, 26, and 28 that are attached in a conventional manner to the structure of the system under test. These acoustic detectors 24, 26 and 28 are preferrably contact accelerometers such as high frequency microphones that have a frequency response of 2.5 KHz to 35 KHz with a rise time of 10-5 seconds or less. Detectors 24, 26 and 28 are connected by leads 30, 32 and 34 to instrumentation control containers 36, 38 and 40. Each instrumentation control container includes an accelerometer drive for its respective detector and conditioning amplifier means. The output from the conditioning amplifier means is connected by leads 42, 44, and 46 to recording device 22 for recording the acoustics detected by detectors 24, 26 and 28 to establish times t1, t2, and t3. If desired, instrumentation control containers 36, 38 and 40 can contain fiber optic drives and fiber optic controls as are conventional in this type art for coupling the information. It is noted that detectors 24, 26, and 28 have been arbitrarily located as indicated, and the indicated locations work well. Since the location of the electrostatic discharge event relative to the acoustic detectors is to be determined, it is not desired to place the acoustic detectors close together or in a straight line. The first signal to reach each of detectors 24, 26 and 28 is the only useful signal that is used in determining the location of the electrostatic discharge event. There may be many standing waves set up in the material and the second, third, etc., wave may be detected until the signals are difficult to distinguish from background clutter. These signals may be useful in establishing the strength of the electrostatic discharge event; however, this particular feature is not of particular interest to this invention.

In operation, when an electrostatic discharge event occurs in structure 10, the event is detected at antenna 14 of electromagnetic pickup 12 and the signal triggers recording device 22 to start the time at t=0 as illustrated. The time required for the signal to travel from the location of the electrostatic discharge event to the location of the antenna of the electromagnetic pickup has been neglected. This time is of the order of a few nanoseconds. Some time later, after time t=0, say t1, an acoustic signal from the electrostatic discharge event is detected by the closest detector of detectors 24, 26, and 28. If the velocity of sound is V, then the distance X from this detector to the electrostatic discharge event's location is given by X1 =Vt1. Therefore, the electrostatic discharge event occurs somewhere on the surface of a sphere centered at the location of this particular detector with a radius of X1. The next detector of detectors 24, 26 and 28 to receive the signal determines a time t2 as illustrated and is located distance X2 =Vt.sub. 2. This electrostatic discharge event is therefore also located on the surface of a sphere centered at the location of the second closest detector with a radius of X2. Thus, the electrostatic discharge event is located on a circle which is the innersection of these two spheres. The fartherest detector of detectors 24, 26 and 28 reoeives the signal at time t3 and likewise determines a sphere, of radius X3 =Vt3, on the surface of which the eleotrostatic discharge event also occurs. The surface of this third sphere also intersects the above circles at only one point. This common point of the three spheres locates where the electrostatic discharge event took place.

The location of the electrostatic discharge event is described mathematically below. The first detector assumes a right handed coordinate system X, Y, Z, and that t1 <t2 <t3. Let the first detector be located at (-h1, 0, 0), the second detector be located at (h1, 0, 0), the third detector be located at (0, h2, h3). Here the X axis has been chosen so that both the first detector and the second detector are located on it. Now if the event occurs at (X, Y, Z) then the three shares on which the event is located are given by ##STR1## Where X1 =Vt1, X2 =Vt2, and X3 =Vt3 and the solution of this system of equations gives the values of X, Y, and Z for the electrostatic discharge event. The above equations are quadratic, and therefore there are two possible solutions. This ambiguity can be removed by the use of an additional acoustic detector. However, for most applications the three acoustic detectors can be arranged so that one of these solutions falls outside the body being tested. In any event, in practice this data processing can be accomplished by allowing recording device 22 to be a small computer.

In some systems where several materials are used, there exist inhomogenuities and the velocity of sound may not be constant or isotropic. These anisotropic properties can be troublesome, but the systems of concern are known and a knowledge of the materials involved exist. Therefore, these uncertainties can be minimized by calibration techniques.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5107447 *May 16, 1989Apr 21, 1992Hitachi, Ltd.Abnormality diagnosing system and method for a high voltage power apparatus
US5185684 *Mar 28, 1991Feb 9, 1993Eaton CorporationFrequency selective arc detection
US5185685 *Mar 28, 1991Feb 9, 1993Eaton CorporationField sensing arc detection
US5185686 *Mar 28, 1991Feb 9, 1993Eaton CorporationDirection sensing arc detection
US5185687 *Mar 28, 1991Feb 9, 1993Eaton CorporationChaos sensing arc detection
US5208542 *Mar 28, 1991May 4, 1993Eaton CorporationTiming window arc detection
US5214595 *Nov 7, 1991May 25, 1993Hitachi, Ltd.Abnormality diagnosing system and method for a high voltage power apparatus
US5432455 *Sep 6, 1994Jul 11, 1995Blades; Frederick K.Method and apparatus for detecting arcing in alternating current power systems by monitoring high-frequency noise
US5434509 *Sep 6, 1994Jul 18, 1995Blades; Frederick K.Method and apparatus for detecting arcing in alternating-current power systems by monitoring high-frequency noise
US5452223 *Aug 20, 1993Sep 19, 1995Eaton CorporationArc detection using current variation
US5561605 *May 10, 1995Oct 1, 1996Eaton CorporationArc detection using current variation
US5590012 *Mar 30, 1995Dec 31, 1996Siemens Energy & Automation, Inc.Electric arc detector sensor circuit
US5682101 *Feb 13, 1996Oct 28, 1997Square D CompanyArcing fault detection system
US5706159 *May 31, 1995Jan 6, 1998Siemens Energy & Automation, Inc.Circuit interrupter including an electric arc monitoring circuit
US5729145 *May 2, 1995Mar 17, 1998Siemens Energy & Automation, Inc.Method and apparatus for detecting arcing in AC power systems by monitoring high frequency noise
US5825598 *Feb 11, 1997Oct 20, 1998Square D CompanyArcing fault detection system installed in a panelboard
US5834940 *Sep 24, 1996Nov 10, 1998Brooks; Stanley J.Arcing fault detector testing and demonstration system
US5839092 *Mar 26, 1997Nov 17, 1998Square D CompanyArcing fault detection system using fluctuations in current peaks and waveforms
US5847913 *Feb 21, 1997Dec 8, 1998Square D CompanyTrip indicators for circuit protection devices
US5923160 *Apr 19, 1997Jul 13, 1999Lucent Technologies, Inc.Electrostatic discharge event locators
US5946179 *Mar 25, 1997Aug 31, 1999Square D CompanyElectronically controlled circuit breaker with integrated latch tripping
US5986860 *Feb 19, 1998Nov 16, 1999Square D CompanyZone arc fault detection
US6034611 *Feb 4, 1997Mar 7, 2000Square D CompanyElectrical isolation device
US6195241Mar 7, 1997Feb 27, 2001Squares D CompanyArcing fault detection system
US6242993Feb 6, 1997Jun 5, 2001Square D CompanyApparatus for use in arcing fault detection systems
US6246556Feb 19, 1998Jun 12, 2001Square D CompanyElectrical fault detection system
US6259996Aug 5, 1998Jul 10, 2001Square D CompanyArc fault detection system
US6313641Jul 1, 1999Nov 6, 2001Square D CompanyMethod and system for detecting arcing faults and testing such system
US6313642Jan 24, 1997Nov 6, 2001Square D CompanyApparatus and method for testing an arcing fault detection system
US6377427Dec 17, 1999Apr 23, 2002Square D CompanyArc fault protected electrical receptacle
US6452767Jan 27, 1997Sep 17, 2002Square D CompanyArcing fault detection system for a secondary line of a current transformer
US6466032 *May 11, 2001Oct 15, 2002Siemens AktiengesellschaftMethod and apparatus for identification of the disconnection of a protection device
US6477021Dec 21, 1999Nov 5, 2002Square D CompanyBlocking/inhibiting operation in an arc fault detection system
US6481280Nov 23, 1999Nov 19, 2002Alstom HoldingsMethod and a device for detecting an internal arc in a metal-clad electrical link
US6532424Apr 11, 2000Mar 11, 2003Square D CompanyElectrical fault detection circuit with dual-mode power supply
US6567250Dec 22, 1999May 20, 2003Square D CompanyArc fault protected device
US6581462Jul 1, 2002Jun 24, 2003Alstom HoldingsMethod and a device for detecting an internal arc in a metal-clad electrical link
US6591482Nov 17, 2000Jul 15, 2003Square D CompanyAssembly methods for miniature circuit breakers with electronics
US6621669Dec 17, 1999Sep 16, 2003Square D CompanyArc fault receptacle with a feed-through connection
US6625550Oct 26, 1999Sep 23, 2003Square D CompanyArc fault detection for aircraft
US6782329Jan 17, 2001Aug 24, 2004Square D CompanyDetection of arcing faults using bifurcated wiring system
US7068480Mar 27, 2002Jun 27, 2006Square D CompanyArc detection using load recognition, harmonic content and broadband noise
US7071701 *Mar 5, 2004Jul 4, 2006New Jersey Institute Of TechnologyOnline fiber optic sensor for detecting partial discharge and similar events in large utility station transformers and the like
US7136265May 13, 2003Nov 14, 2006Square D CompanyLoad recognition and series arc detection using bandpass filter signatures
US7151656Oct 17, 2001Dec 19, 2006Square D CompanyArc fault circuit interrupter system
US7161873 *Mar 25, 2005Jan 9, 2007Areva T&D SaMethod of detecting and locating a source of partial discharge in an electrical apparatus
US7253637Sep 13, 2005Aug 7, 2007Square D CompanyArc fault circuit interrupter system
EP1004884A1 *Nov 23, 1999May 31, 2000Alstom HoldingsMethod and device for the detection of internal arcing in an electric conductor in a metal casing
EP1707970A1 *Mar 27, 2006Oct 4, 2006Areva T&D SaMethod for detecting the position of a wave front in a signal received by a detector
WO1997024742A1 *Dec 27, 1996Jul 10, 1997Kurt BrungardtMethod and apparatus for locating partial discharge in electrical transformers
Classifications
U.S. Classification324/456, 324/520, 324/536
International ClassificationG01N29/24, G01R31/12, G01N29/14
Cooperative ClassificationG01N29/14, G01R31/1209, G01N29/2412, G01N2291/011
European ClassificationG01N29/24B, G01R31/12D, G01N29/14
Legal Events
DateCodeEventDescription
Jun 3, 1988ASAssignment
Effective date: 19860710
Owner name: UNITED STATES OF AMERICA, THE, AS REPRESENTED BY T
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:STRICKLAND, BRIAN R.;EDLIN, GEORGE R.;REEL/FRAME:004897/0072