US3976987A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dual channel dynamic line isolation monitor
Assignee: Schneider Electric USA Inc
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Filing: 1975-08-29
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Granted: 1976-08-24
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Expires: 1995-08-29
Abstract
Abstract A line isolation monitor for indicating the maximum hazard current in an ungrounded power distribution system with conductor lines having leakage impedances. A signal proportional to the maximum voltage to ground of any of the conductor lines in the system is determined and used as a reference voltage for the monitor. Separate circuits each responsive to the reference voltage generate respectively a capacitive component signal and a resistive component signal which are combined and applied as a measurement signal across the system leakage impedances in parallel. The impedance voltage response to the measurement current is separated from the line voltage signal, phase shifted and compared to the reference voltage signal to produce a difference signal which is used to control the magnitude of both the capacitive component signal and the resistive component signal. The magnitude of the combined capacitive component signal and the resistive component signal represents the maximum hazard current.
Inventors
- 👤 Ernest G. Anger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:13
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/16; G01R27/18; G01R31/00; G01R31/50; G01R31/52; G01R31/58
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
94 words
A monitor for use with an ungrounded power distribution system with conductor lines having impedance leakages comprising: detector means for generating a reference voltage; current means responsive to said reference voltage for applying a measurement current to said system; feedback means connected to said system for determining the voltage response of said impedance leakages to said measurement current; said feedback means connected to said current means for adjusting the phase and magnitude of said measurement current; and output means responsive to said current means for indicating the completeness of said system's isolation from ground.
Claim 2
Dependent Claim
94 words
A monitor for use with an ungrounded power distribution system with conductor lines having impedance leakages comprising: detector means for generating a reference voltage; current means responsive to said reference voltage for applying a measurement current to said system; feedback means connected to said system for determining the voltage response of said impedance leakages to said measurement current; said feedback means connected to said current means for adjusting the phase and magnitude of said measurement current; and output means responsive to said current means for indicating the completeness of said system's isolation from ground.
Claim 3
Dependent Claim
38 words
A monitor as set forth in claim 1 wherein said detector means is responsive to said system and said reference voltage is proportional to the maximum voltage to ground of any of said conductor lines in said system.
Claim 4
Dependent Claim
82 words
A monitor as set forth in claim 2 wherein said detector means comprises: a monitor transformer connected to said system and having a tapped primary and tapped secondary winding; amplifier means having an input and output with said input connected to said tap of said primary; the output of said amplifier means connected to said tap of said secondary; rectifying means connected to said secondary winding for combining said output of said amplifier means with the opposite polarity signal across said secondary.
Claim 5
Dependent Claim
40 words
A monitor as set forth in claim 1 wherein said current means comprises: a capacitive circuit channel for generating a capacitive component of said measurement current; and a resistive circuit channel for generating a resistive component of said measurement current.
Claim 6
Dependent Claim
42 words
A monitor as set forth in claim 4 further comprising: a summation means for combining said capacitive component and said resistive component of said measurement current; and means responsive to said summation means for applying said measurement current to said leakage impedances.
Claim 7
Dependent Claim
27 words
A monitor as set forth in claim 5 wherein the frequency of said measurement current is different than the frequency of the line current of said system.
Claim 8
Dependent Claim
51 words
A monitor as set forth in claim 6 wherein said summation circuit combines said capacitive component at a ratio to compensate for the proportionally variable response of capacitive impedance with frequency whereby said feedback voltage response will represent the voltage response of the capacitive impedance leakage to said different line frequency.
Claim 9
Dependent Claim
22 words
A monitor as set forth in claim 4 wherein said capacitive channel and said resistive channel each comprise a commutated integrator circuit.
Claim 10
Dependent Claim
66 words
A monitor as set forth in claim 8 wherein said commutated integrator circuit comprises: an operational amplifier with a feedback path; subtractive comparison means in said feedback path for generating an input voltage signal to said amplifier representing the difference between said voltage reference and said impedance voltage response; and switch means in said feedback path for causing said amplifier to produce an AC output signal.
Claim 11
Dependent Claim
38 words
A monitor as set forth in claim 9 wherein the conduction of said switch means in each of said commutated integrators is synchronously timed for producing said AC output signal of each of said amplifiers in phase quadrature.
Claim 12
Dependent Claim
73 words
A monitor as set forth in claim 4 wherein said output means comprises: an output summation means for combining said capacitive component of said measurement current and said resistive component of said measurement current; a meter circuit for receiving said measurement current whereby the maximum magnitude of line current flow through said impedance leakages is indicated, amplifier means responsive to said output summation means for applying said measurement current to said meter circuit.
Claim 13
Dependent Claim
39 words
A monitor as set forth in claim 11 wherein said output means further comprises: time delay means responsive to said measurement current; relay means responsive to said time delay means; and sensory alarm means connected to said relay means.
Claim 14
Dependent Claim
28 words
A monitor as set forth in claim 12 wherein said output means further comprises: transient overload protection means connected between said time delay means and said relay means.
Claim 15
Dependent Claim
34 words
A monitor as set forth in claim 13 wherein said output means further comprises: ground loss detection means connected to said meter circuit whereby loss of said meter circuit ground energizes said alarm means.
Claim 16
Dependent Claim
69 words
A monitor as set forth in claim 1 wherein said feedback means comprises: input means to determine the voltage response of said impedance leakages to said measurement current; filter means for separating said feedback voltage response from the line voltage of said system and for phase shifting said feedback voltage; amplifier means connected to said filter means for applying said phase shifted feedback voltage signal to said current means.
Claim 17
Dependent Claim
35 words
A monitor as set forth in claim 1 wherein said output means comprises: a meter circuit for receiving said measurement current whereby the maximum magnitude of fault current flow through said system leakages is indicated.
Claim 18
Dependent Claim
27 words
A monitor as set forth in claim 1 wherein the frequency of said measurement current is different than the frequency of the line current of said system.
Claim 19
Dependent Claim
139 words
A monitor for indicating the maximum hazard current in an ungrounded power distribution system with conductor lines having leakage impedances comprising: detector means responsive to said system to generate a reference voltage proportional to the maximum voltage to ground of any of said conductor lines in said system; current means responsive to said reference voltage for separately generating a capacitive component signal and a resistive component signal, combining said signals to form a measurement current signal and applying said measurement current signal to said system; feedback means connected to said system for determining the voltage response signal of said leakage impedances to said measurement current signal; said voltage response signal connected to said current means for adjusting the phase and magnitude of said measurement current; and output means responsive to said measurement current for indicating said maximum hazard current.
Claim 20
Dependent Claim
139 words
A monitor for indicating the maximum hazard current in an ungrounded power distribution system with conductor lines having leakage impedances comprising: detector means responsive to said system to generate a reference voltage proportional to the maximum voltage to ground of any of said conductor lines in said system; current means responsive to said reference voltage for separately generating a capacitive component signal and a resistive component signal, combining said signals to form a measurement current signal and applying said measurement current signal to said system; feedback means connected to said system for determining the voltage response signal of said leakage impedances to said measurement current signal; said voltage response signal connected to said current means for adjusting the phase and magnitude of said measurement current; and output means responsive to said measurement current for indicating said maximum hazard current.
Claim 21
Dependent Claim
42 words
A monitor as set forth in claim 18 wherein said current means comprises: a capacitive circuit channel for generating said capacitive component signal of said measurement current; and a resistive circuit channel for generating said resistive component signal of said measurement current.
Claim 22
Dependent Claim
23 words
A monitor as set forth in claim 19 wherein said capacitive component signal and said resistive component signal are generated in phase quadrature.
Claim 23
Dependent Claim
52 words
A monitor as set forth in claim 19 further comprising: filter means for phase shifting said impedance voltage response signal; and amplifier means for applying said phase shifted impedance voltage response signal to both said capacitive circuit channel and said resistive circuit channel for respectively adjusting the magnitude of said component signals.
Claim 24
Independent Claim
114 words
A method of monitoring the maximum hazard current of an ungrounded power distribution system with conductor lines having leakage impedance comprising: generating a reference voltage signal proportional to the maximum voltage to ground of any of said conductor lines of said system; generating a measurement current signal in response to said reference voltage signal; applying said measurement current signal across said impedance leakage of said system; determining the voltage response signal produced across said leakage impedance to said measurement current signal; applying said voltage response signal to modify the measurement current signal; and monitoring the magnitude of said measurement current signal whereby the magnitude of said measurement current signal represents said maximum hazard current.
Claim 25
Independent Claim
114 words
A method of monitoring the maximum hazard current of an ungrounded power distribution system with conductor lines having leakage impedance comprising: generating a reference voltage signal proportional to the maximum voltage to ground of any of said conductor lines of said system; generating a measurement current signal in response to said reference voltage signal; applying said measurement current signal across said impedance leakage of said system; determining the voltage response signal produced across said leakage impedance to said measurement current signal; applying said voltage response signal to modify the measurement current signal; and monitoring the magnitude of said measurement current signal whereby the magnitude of said measurement current signal represents said maximum hazard current.
Claim 26
Dependent Claim
52 words
A method as set forth in claim 22 wherein generating a measurement current signal comprises: generating a capacitive component signal of said measurement current signal, generating a resistive component signal of said measurement current signal; and combining said capacitive component signal and said resistive component signal to form said measurement current signal.
Claim 27
Dependent Claim
55 words
A method as set forth in claim 23 wherein applying said voltage response signal comprises: separating said impedance voltage response signal from the line voltage signal; phase shifting said impedance voltage response signal; and applying said phase shifted voltage response signal to adjust the magnitude of said capacitive component signal and said resistive component signal.
Claim 28
Dependent Claim
141 words
Apparatus for monitoring the maximum hazard current of an ungrounded power distribution system with conductor lines having leakage impedances comprising: detector means for determining the maximum voltage to ground signal of any of said conductor lines of said system; current means for applying a measurement current across said leakage impedances to produce an impedance voltage signal; feedback means for detecting said impedance voltage; circuit means responsive to said detector means and said feedback means for comparing said impedance voltage signal to said maximum voltage to ground signal; said circuit means connected to said current means for varying said measurement current until said impedance voltage signal times a constant equals said maximum voltage signal; and output means responsive to said current means for indicating the magnitude of said measurement current times said constant whereby said indicated signal represents said maximum hazard current.
Claim 29
Dependent Claim
141 words
Apparatus for monitoring the maximum hazard current of an ungrounded power distribution system with conductor lines having leakage impedances comprising: detector means for determining the maximum voltage to ground signal of any of said conductor lines of said system; current means for applying a measurement current across said leakage impedances to produce an impedance voltage signal; feedback means for detecting said impedance voltage; circuit means responsive to said detector means and said feedback means for comparing said impedance voltage signal to said maximum voltage to ground signal; said circuit means connected to said current means for varying said measurement current until said impedance voltage signal times a constant equals said maximum voltage signal; and output means responsive to said current means for indicating the magnitude of said measurement current times said constant whereby said indicated signal represents said maximum hazard current.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-08-24 | 1980-02-23 | 1980-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-24 | 1984-02-23 | 1984-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-24 | 1988-02-23 | 1988-08-24 | $7700.00 | Window Closed / Lapsed |