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US5508620A
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Method and device for determining ground faults on the conductors of an electrical machine
Assignee: ABB Schweiz AG
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Filing: 1994-07-26
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Granted: 1996-04-16
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Expires: 2014-07-26
Abstract
Abstract A method is specified for detecting ground faults on the conductors of electrical machines, in which method the fault resistance (Rf) is directly calculated in a numerical evaluation unit (7) from the injected (Ui) and the measured (URE) voltages. Since the fault resistance is explicitly calculated and displayed, it is independent of influences from the ground reactance. Moreover, there is no need to, for each machine, characteristics for drawing conclusions on the fault resistance. Moreover, the influence of ageing, temperature fluctuations, injection level fluctuations etc. is eliminated due to the numerical calculation. (FIG. 1a)
Inventors
- 👤 Michael Pfiffner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 14:59
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/34; G01R31/346; G01R27/00; G01R27/02; G01R27/16; G01R27/18
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
164 words
A method for detecting ground faults on conductors of an electrical machine, the method comprising the steps of: a) biasing the conductors with respect to ground potential by means of a low-frequency injection voltage U i of frequency f 1 , and measuring and evaluating a measuring voltage U RE via a ground resistor R E connected to the conductors; b) calculating a ground fault resistance R f from the injection voltage U i and the measuring voltage U RE , and numerically displaying said ground fault resistance R f in a numerical evaluation unit connected to the measuring voltage; the conductors being the stator windings of said electrical machine connected in star; c) dividing the injected and measured voltages U i and U RE in the evaluation unit into orthogonal components U ix , U iy , and U REx , U REy , respectively; and d) calculating the ground fault resistance R f in the evaluation unit in accordance with: ##EQU6## .
Claim 2
Independent Claim
164 words
A method for detecting ground faults on conductors of an electrical machine, the method comprising the steps of: a) biasing the conductors with respect to ground potential by means of a low-frequency injection voltage U i of frequency f 1 , and measuring and evaluating a measuring voltage U RE via a ground resistor R E connected to the conductors; b) calculating a ground fault resistance R f from the injection voltage U i and the measuring voltage U RE , and numerically displaying said ground fault resistance R f in a numerical evaluation unit connected to the measuring voltage; the conductors being the stator windings of said electrical machine connected in star; c) dividing the injected and measured voltages U i and U RE in the evaluation unit into orthogonal components U ix , U iy , and U REx , U REy , respectively; and d) calculating the ground fault resistance R f in the evaluation unit in accordance with: ##EQU6## .
Claim 3
Dependent Claim
64 words
A device for carrying out the method as claimed in claim 1, wherein a) the injection voltage is fed into a star point from an injection signal source via an injection transformer, a parallel resistor and the ground resistor; and b) a measuring transformer, whose output is connected to the input of the numerical evaluation unit, is provided in parallel with the ground resistor.
Claim 4
Dependent Claim
25 words
The device as claimed in claim 2, wherein the ground resistor and the parallel resistor are connected to the star point via a grounding transformer.
Claim 5
Dependent Claim
66 words
A device for carrying out the method as claimed in claim 1, wherein a) the injection voltage is fed into the conductors from an injection signal source via an injection transformer, a parallel resistor, the ground resistor and a grounding transformer; and b) a measuring transformer, whose output is connected to the input of the numerical evaluation unit, is provided in parallel with the ground resistor.
Claim 6
Independent Claim
195 words
A method for detecting ground faults on conductors of an electrical machine, the method comprising the steps of: a) biasing the conductors with respect to ground potential by means of a low-frequency injection voltage U i of frequency f 1 , and measuring and evaluating a measuring voltage U RE via a ground resistor R E connected to the conductors; b) calculating a ground fault resistance R f from the injection voltage U i and the measuring voltage U RE , and numerically displaying said ground fault resistance R f in a numerical evaluation unit connected to the measuring voltage, the conductors being the rotor windings of said electrical machine and said injection voltage U i being fed into the terminals of the rotor windings via coupling capacitors; c) dividing the injected and measured voltages U i and U RE in the evaluation orthogonal components U ix , U iy , and U REx , U REy , respectively; and d) calculating the ground fault resistance R f in the evaluation unit in accordance with: ##EQU7## where U Ckx and U Cky represent orthogonal components of a voltage U Ck measured over said coupling capacitors.
Claim 7
Independent Claim
195 words
A method for detecting ground faults on conductors of an electrical machine, the method comprising the steps of: a) biasing the conductors with respect to ground potential by means of a low-frequency injection voltage U i of frequency f 1 , and measuring and evaluating a measuring voltage U RE via a ground resistor R E connected to the conductors; b) calculating a ground fault resistance R f from the injection voltage U i and the measuring voltage U RE , and numerically displaying said ground fault resistance R f in a numerical evaluation unit connected to the measuring voltage, the conductors being the rotor windings of said electrical machine and said injection voltage U i being fed into the terminals of the rotor windings via coupling capacitors; c) dividing the injected and measured voltages U i and U RE in the evaluation orthogonal components U ix , U iy , and U REx , U REy , respectively; and d) calculating the ground fault resistance R f in the evaluation unit in accordance with: ##EQU7## where U Ckx and U Cky represent orthogonal components of a voltage U Ck measured over said coupling capacitors.
Claim 8
Dependent Claim
67 words
A device for carrying out the method as claimed in claim 5, wherein a) the injection voltage is fed into the rotor terminals from an injection signal source via an injection transformer, a parallel resistor, the ground resistor and two coupling capacitors; and b) a measuring transformer, whose output is connected to the input of the numerical evaluation unit, is provided in parallel with the ground resistor.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1999-04-16 | 1999-10-16 | 2000-04-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-04-16 | 2003-10-16 | 2004-04-16 | $3760.00 | Window Closed / Lapsed |
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