US4200835A
Expired / Lapsed
US
⏱️ 0.0 years remaining
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 10:41
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.
References Cited (Backward Citations)
US2923879A
Cited
US3678376A
Cited
US3710238A
Cited
US3774106A
Cited
US3866117A
Cited
US3971007A
Cited
US3842344A
Cited
US3891895A
Cited
US3978465A
Cited
US4066950A
Cited
US4112354A
Cited
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 |