US3757169A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dynamic ground detector
Assignee: Stackpole Ltd
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Filing: 1972-05-15
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Granted: 1973-09-04
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Expires: 1992-05-15
Abstract
Abstract A dynamic ground detector for monitoring a two-wire power distribution system, where both sides are nominally isolated from ground. A sampling bridge is connected between the lines, each shunt section of the bridge comprising a resistor and a capacitor having impedances in quadriture at the line frequency; and the junctions of the shunt sections of the sampling bridge are alternatively sampled by a switching network. The switching network connected through a phase shifting network comprising an RC filter to a detector network comprising a fullwave rectifier with suitable indicator and alarm apparatus. The rate of sampling is a multiple, including unity, of the line frequency. Additional circuitry may also be provided for sensing the direction and phase of any fault current caused by a fault to ground from either or both of the lines, so that the fault current may be opposed by insertion of another current having the same phase and opposite direction.
Inventors
- 👤 V Beresnikow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 21:54
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/08; G; G01; G01R; G01R27/00; G01R27/02; G01R27/16; G01R27/18; G01R31/00; G01R31/50; G01R31/52
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
288 words
Apparatus for monitoring a two-wire power distribution system, where both sides of the system are nominally isolated from ground, and for detecting balanced and unbalanced faults to ground within the system, any such detected fault occurring within the system being a connection of an impedance between ground and at least one side of the system, comprising: first and second pairs of impedances connected between the sides of said system, where each pair comprises a resistor and a capacitor whose value is chosen so that its impedance at the line frequency of the system is substantially equal to the impedance of the resistor; the first and second pairs of impedances being connected to the system so that the resistor of said first pair and the capacitor of said second pair are connected to one side of the system, and the capacitor of the first pair and the resistor of the second pair are connected to the other side of the system; the junction points between the impedances of each of said first and second pairs of impedances being alternately connectable to a detector circuit through a sampling network; the rate of connecting said junction points to said detector circuit being a multiple, including unity, of the line frequency of said system; means for changing the phase angle of any signal being fed to said detector circuit from said sampling network so that the phase angle of such signal is different than the phase angle of a signal derived from the junction point of either of said first or secoNd pairs of impedances; said detector circuit being connected to ground and including means for continuously feeding any signal derived through the sampling network from said system to said indicator means.
Claim 2
Dependent Claim
288 words
Apparatus for monitoring a two-wire power distribution system, where both sides of the system are nominally isolated from ground, and for detecting balanced and unbalanced faults to ground within the system, any such detected fault occurring within the system being a connection of an impedance between ground and at least one side of the system, comprising: first and second pairs of impedances connected between the sides of said system, where each pair comprises a resistor and a capacitor whose value is chosen so that its impedance at the line frequency of the system is substantially equal to the impedance of the resistor; the first and second pairs of impedances being connected to the system so that the resistor of said first pair and the capacitor of said second pair are connected to one side of the system, and the capacitor of the first pair and the resistor of the second pair are connected to the other side of the system; the junction points between the impedances of each of said first and second pairs of impedances being alternately connectable to a detector circuit through a sampling network; the rate of connecting said junction points to said detector circuit being a multiple, including unity, of the line frequency of said system; means for changing the phase angle of any signal being fed to said detector circuit from said sampling network so that the phase angle of such signal is different than the phase angle of a signal derived from the junction point of either of said first or secoNd pairs of impedances; said detector circuit being connected to ground and including means for continuously feeding any signal derived through the sampling network from said system to said indicator means.
Claim 3
Dependent Claim
93 words
The apparatus of claim 1 wherein said sampling network includes a pair of bi-directional gate-controlled solid state devices, with a first end of each such device connected to the junction of one of said pairs of impedances, and a second end of each such device connected to said phase angle changing means; a gate connection of each of said devices being connected to a discrete source of gate voltage operable to make each such device conductive or non-conductive at a rate being a multiple, including unity, of the line frequency of said sytem.
Claim 4
Dependent Claim
30 words
The apparatus of claim 2 wherein said detector circuit includes a full-wave rectifier bridge connected between said phase angle changing means and ground, with indicator means connected across said bridge.
Claim 5
Dependent Claim
33 words
The apparatus of claim 1 further including: alarm means connected to said indicator means, trigger means to cause said alarm to be operable at a preset level of current in said detector circuit.
Claim 6
Dependent Claim
47 words
The apparatus of claim 2 wherein said detector circuit includes shunt means having a variable impedance dependent on the line voltage of said system, and connected across said indicator means so as to alter the sensitivity thereof substantially in direct proportion to a change of line voltage.
Claim 7
Dependent Claim
51 words
The apparatus of claim 2 where the voltage at each junction of said pair of impedances lags the current at that junction by substantially 45*, and the voltage of the signal applied to said detector circuit from said phase angle changing means lags the current of such signal by substantially 81*.
Claim 8
Dependent Claim
25 words
The apparatus of claim 2 further including: sensing and comparator means for determining the phase angle and direction of any current in said detector circuit.
Claim 9
Dependent Claim
61 words
The apparatus of claim 7 further including: means for inserting into said two-wire system a current of opposite direction and the same phase angle as the current in the detector circuit, said means comprising an amplifier and current inverter, a gated compensation bridge between said two lines of said system, and a source of gating voltage for said gating compensation bridge.
Claim 10
Dependent Claim
28 words
The apparatus of claim 8 where the gating voltage from said source of gating voltage is at the same rate as the gating voltage of said sampling network.
Claim 11
Dependent Claim
54 words
The apparatus of claim 4, further including a grounding connection monitor comprising: a second detector network connected in series with the ground connection of the detector circuit and ground, the output of said second detector network being applied to amplifier means, and the output of said amplifier means being connected to said alarm means.
Claim 12
Dependent Claim
43 words
The apparatus of claim 10, wherein said second detector network is a rectifier bridge, and said amplifier is connected as a zero-current detector amplifier so that, on loss of ground connection by said detector circuit, said alarm means is triggered to alarm status.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |