Patent US793635A successfully refreshed from Google Patents.
US4200835A
Expired / Lapsed
US
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Method and apparatus for measuring the insulation resistance of an operating grounded transmission line system
Assignee: Fuji Electric Co Ltd
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Filing: 1978-05-30
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Granted: 1980-04-29
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Expires: 1998-05-30
Abstract
Abstract By introducing a secondary voltage having a lower frequency than the principal voltage in a grounded transmission line system, detecting the current arising from such secondary voltage only and multiplying such current by the magnitude of the secondary voltage a resultant signal is obtained which is proportional to the inverse of the insulation resistance of the system.
Inventors
- 👤 Ryoji Anahara
- 👤 Koichi Sato
- 👤 Motoshiro Kaneda
- 👤 Mitsuo Saito
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:58
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/025; G01R27/16; G01R27/18; G01R31/00; G01R31/50; G01R31/58; H; H02; H02H; H02H3/00; H02H3/16; H02H3/17
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
106 words
The method of measuring insulation resistance in an operating, grounded a.c. power transmission system carrying electrical power at a first frequency which includes the steps of: injecting into the transmission system in series with grounding means therein an electrical voltage at a secondary frequency much lower than said first frequency; detecting the level of resistive current flowing in said grounding means in said transmission system as a result of the injection of electrical voltage at said secondary frequency; and multiplying a voltage representative of said injected voltage by a voltage representative of said detected resistive current to give a product voltage representative of said insulation resistance.
Claim 2
Independent Claim
106 words
The method of measuring insulation resistance in an operating, grounded a.c. power transmission system carrying electrical power at a first frequency which includes the steps of: injecting into the transmission system in series with grounding means therein an electrical voltage at a secondary frequency much lower than said first frequency; detecting the level of resistive current flowing in said grounding means in said transmission system as a result of the injection of electrical voltage at said secondary frequency; and multiplying a voltage representative of said injected voltage by a voltage representative of said detected resistive current to give a product voltage representative of said insulation resistance.
Claim 3
Dependent Claim
20 words
The method according to claim 1 which includes the additional step of displaying the product voltage as a resistance measurement.
Claim 4
Dependent Claim
21 words
The method of claim 1 including the additional step of actuating an alarm when said product voltage exceeds a predetermined level.
Claim 5
Dependent Claim
135 words
Apparatus for the measurement of the insulation resistance in an operating, grounded a.c. transmission line system carrying power at a first frequency, and having grounding means including: a source of a secondary voltage at a second frequency lower than said first frequency; injection means coupled in series with said grounding means of said source and to said transmission line system for injecting said secondary voltage into said transmission line system; detecting means coupled to said transmission line system for detecting the secondary current produced in said grounding means of said transmission line system by said secondary voltage; and multiplying means coupled to said detecting means and to said source for multiplying a voltage representative of said secondary voltage by a voltage representative of said secondary current to produce a voltage representative of said insulation resistance.
Claim 6
Dependent Claim
135 words
Apparatus for the measurement of the insulation resistance in an operating, grounded a.c. transmission line system carrying power at a first frequency, and having grounding means including: a source of a secondary voltage at a second frequency lower than said first frequency; injection means coupled in series with said grounding means of said source and to said transmission line system for injecting said secondary voltage into said transmission line system; detecting means coupled to said transmission line system for detecting the secondary current produced in said grounding means of said transmission line system by said secondary voltage; and multiplying means coupled to said detecting means and to said source for multiplying a voltage representative of said secondary voltage by a voltage representative of said secondary current to produce a voltage representative of said insulation resistance.
Claim 7
Dependent Claim
37 words
Apparatus according to claim 4 which includes, in addition, output terminals in said multiplying means across which output terminals said voltage representative of said insulation resistance appears; and, insulation resistance indicating means coupled across said output terminals.
Claim 8
Dependent Claim
53 words
Apparatus according to claim 4 which includes, in addition, output terminals on said multiplying means across which output terminals said voltage representative of said insulation resistance appears; and, alarm means coupled across output terminals and responsive to a predetermined level of said voltage representative of said insulation resistance to produce an alarm signal.
Claim 9
Dependent Claim
54 words
Apparatus according to claim 4 in which said injection means includes a step-down transformer having its primary coupled to said source and its secondary coupled in series with said grounding means of said transmission line system; and a resistor having a value corresponding to the output impedance of said source connected across said primary.
Claim 10
Dependent Claim
13 words
Apparatus according to claim 7 in which said transformer has a saturable core.
Claim 11
Dependent Claim
27 words
Apparatus according to claim 4 in which said injection means includes a high-pass filter coupled between said source and said grounding means of said transmission line system.
Claim 12
Dependent Claim
116 words
Apparatus according to claim 4 in which said detecting means includes a dropping resistor coupled in series with said grounding means in said transmission line system for producing thereacross a voltage corresponding to secondary currents flowing in said system as a result of the injection of said secondary voltage into said system; a phase shifter coupled to said source and to said dropping resistor for introducing a bucking voltage for counteracting the voltage across said resistor arising from the flow of capacitive currents in said system; and a low-pass filter coupled between said phase shifter and said multiplying means for passing only those voltages having a frequency corresponding to the frequency of said secondary voltage source.
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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) | 1983-04-29 | 1983-10-29 | 1984-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-04-29 | 1987-10-29 | 1988-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-04-29 | 1991-10-29 | 1992-04-29 | $7700.00 | Window Closed / Lapsed |