US4291204A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fault locating system for electric cables and the like
Assignee: Tempo Research Corp
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Filing: 1979-08-13
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Granted: 1981-09-22
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Expires: 1999-08-13
Abstract
Abstract A system for locating faults in an electric cable including a flyback transformer or inductor and control circuitry therefor for developing an arc through a high resistance short circuit between two conductors or one conductor and ground. The control circuitry limits the current flow in the arc to avoid burning or welding of the conductors but maintains the current so that the high resistance short appears temporarily as a low resistance short which can be detected. A low level DC bias current stabilizes the system, particularly in the presence of large line capacitance when the distance between the apparatus and the cable fault is large. The circuitry includes an audible tone generator which can be sensed by induction with known inductive pickup equipment. The circuit also allows use of a time domain reflectometer to determine the location of high resistance shorts from a remote location on the cable to which connections can be made.
Inventors
- 👤 Robert G. Crick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:24
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/08; G01R31/10; G01R31/11
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
98 words
A system for locating a high resistance fault between a conductor pair comprising a switchable current pulse source for producing a current pulse at a voltage sufficient to temporarily arc across the fault to form at the fault a temporary arc plasma having a low resistance current path therethrough, nondissipating current limiting means for limiting the current through the low resistance path to limit the power dissipated in the arc so as to avoid fusing the conductor, and detecting means for affording detection of the location of the low resistance path during the presence of the arc plasma.
Claim 2
Independent Claim
98 words
A system for locating a high resistance fault between a conductor pair comprising a switchable current pulse source for producing a current pulse at a voltage sufficient to temporarily arc across the fault to form at the fault a temporary arc plasma having a low resistance current path therethrough, nondissipating current limiting means for limiting the current through the low resistance path to limit the power dissipated in the arc so as to avoid fusing the conductor, and detecting means for affording detection of the location of the low resistance path during the presence of the arc plasma.
Claim 3
Dependent Claim
42 words
A system according to claim 1 wherein said detecting means comprises means for periodically interrupting said pulse source at a rate to facilitate inductive pickup of the current the system causes to flow along said conductor pair and through the arc plasma.
Claim 4
Dependent Claim
25 words
A system according to claim 2 wherein said detecting means comprises a direct current power source so that said interrupting means produces pulsating direct current.
Claim 5
Dependent Claim
63 words
A system according to claim 1 wherein said detecting means includes a time domain reflectometer producing measuring impulses and means for synchronizing the time domain reflectometer with said pulse source so that said time domain reflectometer is active during existence of said arc plasma across the fault and so that said impulses are reflected by the low impedence plasma path across said arc.
Claim 6
Dependent Claim
58 words
A system according to claim 1 wherein said detection means includes means for measuring the current through one of the conductors, means for measuring the voltage across the conductors while the arc plasma is sustained, and means for displaying the quotient of the measured voltage divided by the measured current to display the loop resistance to the fault.
Claim 7
Dependent Claim
54 words
A system according to claim 1 wherein said detecting means includes means for periodically interrupting said pulse source at an audible rate so that an audio frequency current is made to flow through the arc plasma thereby generating sound waves within the plasma to facilitate sonic pickup of current flowing through the arc plasma.
Claim 8
Dependent Claim
53 words
a system according to claim 1 including means for producing a DC bias current to the conductor pair and the arc plasma, said pulses being superimposed on said DC bias current, said current limiting means including means for regularly terminating the DC bias current to afford dissipation of heat from said arc plasma.
Claim 9
Dependent Claim
55 words
A system according to claim 1 wherein said pulse source includes an inductor, means for supplying current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy, and means connecting said conductor pair across said inductor to receive the energy discharged therefrom.
Claim 10
Dependent Claim
97 words
A system according to claim 8 wherein said inductor includes a flyback transformer having a primary winding, a secondary winding and a core flux linking said windings, there being means for coupling said conductor pair across said secondary winding, wherein said current supplying means includes means for gating current flow through said primary windings, and wherein said current limiting means includes means in series with said current supplying means for sensing the magnitude of current flow therethrough and means responsive to said current sensing means for disabling said gating means when the current reaches a preselected magnitude.
Claim 11
Dependent Claim
65 words
A system according to claim 9 wherein said gating means includes means for generating a square wave having a repetition rate with a period less than the decay time of the arc plasma across the fault and wherein said disabling means includes means for reducing the on time of said square wave in response to the magnitude of current sensed by said current sensing means.
Claim 12
Independent Claim
105 words
A system for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as temporarily to produce an arc plasma between the conductors at the high resistance fault, said voltage applying means including a switchable current pulse source, nondissipating means for limiting the current through the arc plasma to limit power so as to avoid damage to the conductors, said nondissipating current limiting means acting to switch said switchable current pulse source, and means for affording detection of the location of the low resistance path through the arc plasma while the arc plasma exists.
Claim 13
Independent Claim
105 words
A system for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as temporarily to produce an arc plasma between the conductors at the high resistance fault, said voltage applying means including a switchable current pulse source, nondissipating means for limiting the current through the arc plasma to limit power so as to avoid damage to the conductors, said nondissipating current limiting means acting to switch said switchable current pulse source, and means for affording detection of the location of the low resistance path through the arc plasma while the arc plasma exists.
Claim 14
Dependent Claim
32 words
A system according to claim 11 wherein said detection affording means comprises means for varying the magnitude of current flow through the arc plasma at a rate to permit inductive pickup thereof.
Claim 15
Dependent Claim
24 words
A system according to claim 12 wherein said current magnitude varying means varies the current flow through the arc plasma at an audible rate.
Claim 16
Dependent Claim
39 words
A system according to claim 13 wherein said current magnitude varying means includes a source of direct current and means for periodically varying said direct current so that only pulsating direct current is caused to flow through said arc.
Claim 17
Dependent Claim
50 words
A system according to claim 11 including bias current producing means associated with said voltage applying means for producing a low level DC bias current through said conductors and said arc plasma, said bias current facilitating maintenance of said arc plasma, said current limiting means limiting said DC bias current.
Claim 18
Dependent Claim
55 words
A system according to claim 11 wherein said voltage applying means includes an inductor, means for supplying current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy, and means connecting the conductors across said inductor to receive the energy discharged therefrom.
Claim 19
Dependent Claim
118 words
A system according to claim 16 wherein said inductor includes a transformer having a core, a primary winding flux linked to the core and a secondary winding flux linked to the core, and wherein said current supplying means includes a pulse source for supplying current pulses to said primary winding, and wherein said flyback causing means includes a switch connected across at least a part of said secondary winding and being controlled by said pulse source so as to short out said secondary winding after termination of current supplied to said primary winding, said conductors being connected across said secondary winding so upon opening of said switch said secondary flies back to apply a voltage across said conductors.
Claim 20
Dependent Claim
48 words
A system according to claim 17 in combination with means for measuring the magnitude of current flow through said arc and means responsive to said current measuring means for deactivating said pulse source when the current flow reaches a preselected magnitude below a magnitude that overheats the conductors.
Claim 21
Dependent Claim
88 words
A system according to claim 17 wherein said pulse source produces repetitive pulses at a relatively high rate so that said transformer flies back at a corresponding rate, filter means in series between said secondary winding and said conductors for filtering said pulses at said relatively high rate, and means for varying the magnitude of said pulses produced at said relatively high rate at an audible rate, said filter means being constructed and arranged to pass signals at said audible rate to facilitate audio detection of said fault.
Claim 22
Dependent Claim
68 words
A system according to claim 19 including means for controllably switching said repetitive pulse source produced at a relatively high rate between an on state and an off state, said on state having a duration sufficient to permit locating said arc plasma with a time domain reflectometer, said off state having a duration sufficient to affort extinguishment of said arc plasma and dissipation of heat at the fault.
Claim 23
Independent Claim
188 words
A system for locating a high resistance short between a pair of conductors comprising a transformer having a secondary winding coupled across the conductors, a primary winding and a core flux linking the primary and secondary windings, a power source and a series connected primary switch connected in series with the primary winding so as to produce a current flow therethrough when the primary switch is closed, means for periodically closing and opening the primary switch so as to produce pulsating current flow through said primary winding, said transformer tending to fly back in response to opening said primary switch, switching means connected across at least a part of said secondary winding for shorting the same during opening of said primary switch so that upon opening of said switching means said transformer flies back to produce a voltage pulse across said secondary winding, said secondary winding having a tap and feedback means connected from said tap to said power source for limiting the voltage at said tap to that of said power source so that the location of said tap establishes the output voltage of said secondary winding.
Claim 24
Independent Claim
188 words
A system for locating a high resistance short between a pair of conductors comprising a transformer having a secondary winding coupled across the conductors, a primary winding and a core flux linking the primary and secondary windings, a power source and a series connected primary switch connected in series with the primary winding so as to produce a current flow therethrough when the primary switch is closed, means for periodically closing and opening the primary switch so as to produce pulsating current flow through said primary winding, said transformer tending to fly back in response to opening said primary switch, switching means connected across at least a part of said secondary winding for shorting the same during opening of said primary switch so that upon opening of said switching means said transformer flies back to produce a voltage pulse across said secondary winding, said secondary winding having a tap and feedback means connected from said tap to said power source for limiting the voltage at said tap to that of said power source so that the location of said tap establishes the output voltage of said secondary winding.
Claim 25
Dependent Claim
44 words
a system according to claim 21 including a second tap on said secondary winding, said second tap being spaced from first said tap, and means for selectively connecting said feedback means to respective said taps to alter the output voltage of said secondary winding.
Claim 26
Independent Claim
168 words
A system for locating a high resistance fault between a conductor pair comprising a pulse source for producing a pulse at a voltage sufficient to arc across the fault to form a low resistance current path therethrough, said pulse source including a flyback transformer having a primary winding, a secondary winding, a core flux linking said windings, a current source for supplying current to said primary winding to store energy in said core and means for gating current flow from said current supplying means through said primary winding; means for connecting said conductor pair across said secondary winding; means for limiting the current through the low resistance path to avoid fusing the conductor, said current limiting means including means in series with said current supplying means for sensing the magnitude of current flow therethrough and means responsive to said current sensing means for disabling said gating means when the current reaches a preselected magnitude; and detecting means for affording detection of the location of the low resistance path.
Claim 27
Independent Claim
168 words
A system for locating a high resistance fault between a conductor pair comprising a pulse source for producing a pulse at a voltage sufficient to arc across the fault to form a low resistance current path therethrough, said pulse source including a flyback transformer having a primary winding, a secondary winding, a core flux linking said windings, a current source for supplying current to said primary winding to store energy in said core and means for gating current flow from said current supplying means through said primary winding; means for connecting said conductor pair across said secondary winding; means for limiting the current through the low resistance path to avoid fusing the conductor, said current limiting means including means in series with said current supplying means for sensing the magnitude of current flow therethrough and means responsive to said current sensing means for disabling said gating means when the current reaches a preselected magnitude; and detecting means for affording detection of the location of the low resistance path.
Claim 28
Dependent Claim
65 words
A system according to claim 23 wherein said gating means includes means for generating a square wave having a repetition rate with a period less than the decay time of the arc plasma across the fault and wherein said disabling means includes means for reducing the on time of said square wave in response to the magnitude of current sensed by said current sensing means.
Claim 29
Independent Claim
171 words
A system for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as to produce an arc between the conductors at the high resistance fault, said voltage applying means including a transformer having a core, a primary winding flux linked to the core, a secondary winding flux linked to the core, a pulse source for supplying current pulses to said primary winding so that the transformer flies back upon termination of each said current pulse, and means for connecting the conductors across the secondary winding to receive energy when said transformer flies back; means for limiting the current through the arc to avoid damage to the conductors, said current limiting means including a switch connected across at least a part of said secondary winding and being controlled by said pulse source so as to short out said secondary winding after termination of current supplied to said primary winding; and means for affording detection of the location of the arc.
Claim 30
Independent Claim
171 words
A system for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as to produce an arc between the conductors at the high resistance fault, said voltage applying means including a transformer having a core, a primary winding flux linked to the core, a secondary winding flux linked to the core, a pulse source for supplying current pulses to said primary winding so that the transformer flies back upon termination of each said current pulse, and means for connecting the conductors across the secondary winding to receive energy when said transformer flies back; means for limiting the current through the arc to avoid damage to the conductors, said current limiting means including a switch connected across at least a part of said secondary winding and being controlled by said pulse source so as to short out said secondary winding after termination of current supplied to said primary winding; and means for affording detection of the location of the arc.
Claim 31
Dependent Claim
48 words
A system according to claim 25 in combination with means for measuring the magnitude of current flow through said arc and means responsive to said current measuring means for deactivating said pulse source when the current flow reaches a preselected magnitude below a magnitude that overheats the conductors.
Claim 32
Independent Claim
140 words
A system for locating a high resistance fault between a conductor pair comprising a pulse source for producing a pulse at a voltage sufficient to temporarily arc across the fault to form at the fault a temporary arc plasma having a low resistance current path therethrough, said pulse source including an inductor, means for supplying current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy and means connecting said conductor pair across said inductor to receive the energy discharged therefrom, means for limiting the current through the low resistance path to limit the power dissipated in the arc so as to avoid fusing the conductor, and detecting means for affording detection of the location of the low resistance path during the presence of the arc plasma.
Claim 33
Independent Claim
140 words
A system for locating a high resistance fault between a conductor pair comprising a pulse source for producing a pulse at a voltage sufficient to temporarily arc across the fault to form at the fault a temporary arc plasma having a low resistance current path therethrough, said pulse source including an inductor, means for supplying current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy and means connecting said conductor pair across said inductor to receive the energy discharged therefrom, means for limiting the current through the low resistance path to limit the power dissipated in the arc so as to avoid fusing the conductor, and detecting means for affording detection of the location of the low resistance path during the presence of the arc plasma.
Claim 34
Dependent Claim
129 words
A systen for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as temporarily to produce an arc plasma between the conductors at the high resistance fault, said voltage applying means including an inductor, means for supplyng current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy and means connecting the conductors across said inductor to receive the energy discharged therefrom, means for limiting the current through the arc plasma to limit power so as to avoid damage to the conductors, and means for affording detection of the location of the low resistance path through the arc plasma while the arc plasma exists.
Claim 35
Dependent Claim
129 words
A systen for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as temporarily to produce an arc plasma between the conductors at the high resistance fault, said voltage applying means including an inductor, means for supplyng current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy and means connecting the conductors across said inductor to receive the energy discharged therefrom, means for limiting the current through the arc plasma to limit power so as to avoid damage to the conductors, and means for affording detection of the location of the low resistance path through the arc plasma while the arc plasma exists.
References Cited (Backward Citations)
GB1155653A
Cited
US3488580A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-09-21 | 1985-03-23 | 1985-09-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-21 | 1989-03-23 | 1989-09-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-21 | 1993-03-23 | 1993-09-22 | $7700.00 | Window Closed / Lapsed |