EP0122366A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Apparatus for detecting ground fault in variable-voltage variable-frequency power system
Assignee: Mitsubishi Electric Corp
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Filing: 1984-01-17
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Granted: —
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Expires: 2004-01-17
Abstract
Abstract An apparatus for detecting a ground fault occurring in a power system which furnishes an AC power from a variable-voltage variable-frequency power supply to a load via a voltage transformer. The apparatus compares a zero phase sequence current with a reference value and, upon detection of occurrence of a ground fault, produces an output signal representing the ground fault. Prior to such comparison, the zero phase sequence current is so processed as to be independent of the frequency of the power system or the reference value is so processed as to be dependent on the said frequency.
Inventors
- 👤 Nobuharu C/O Mitsubishi Denki K.K. Takata
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 22:20
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/16; H02H3/162; G; G01; G01R; G01R27/00; G01R27/02; G01R27/16; G01R27/18; G01R31/00; G01R31/50; G01R31/52
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
88 words
An apparatus (Fig. 3) for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply to a load via a transformer, said apparatus comprising input means (8) for producing a signal of a level corresponding to the frequency of a zero phase sequence current flowing through the neutral point of said transformer, and relay means (9) activated in response to increase of the signal of said input means beyond a predetermined level and serving to protect said power system.
Claim 2
Independent Claim
88 words
An apparatus (Fig. 3) for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply to a load via a transformer, said apparatus comprising input means (8) for producing a signal of a level corresponding to the frequency of a zero phase sequence current flowing through the neutral point of said transformer, and relay means (9) activated in response to increase of the signal of said input means beyond a predetermined level and serving to protect said power system.
Claim 3
Dependent Claim
69 words
The ground fault detecting apparatus as defined in claim 1, wherein said input means includes a current transformer (81) for transforming the current related to the zero phase sequence current according to a predetermined winding ratio, and a capacitor (82) connected across the terminals of the secondary winding of said current transformer in such a manner that the terminal voltage of said capacitor is introduced to the output terminal.
Claim 4
Independent Claim
121 words
An apparatus (Fig. 4) for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply (2) to a load via a transformer, said apparatus comprising first input means (IND3) for processing a zero phase sequence current flowing in the neutral point of said transformer and producing a comparison signal equivalent to a predetermined multiple of said current, second input means (G, IND2) for processing the voltage signal related to the state of said load and producing a reference signal equivalent to a predetermined multiple of said voltage signal, and relay means (14) activated in response to increase of said comparison signal above said reference signal and serving to protect said power system.
Claim 5
Independent Claim
121 words
An apparatus (Fig. 4) for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply (2) to a load via a transformer, said apparatus comprising first input means (IND3) for processing a zero phase sequence current flowing in the neutral point of said transformer and producing a comparison signal equivalent to a predetermined multiple of said current, second input means (G, IND2) for processing the voltage signal related to the state of said load and producing a reference signal equivalent to a predetermined multiple of said voltage signal, and relay means (14) activated in response to increase of said comparison signal above said reference signal and serving to protect said power system.
Claim 6
Dependent Claim
52 words
The ground fault detecting apparatus (Fig. 5) as defined in claim 3, wherein said load consists of a motor, and said second input means comprises a pilot generator connected to said motor and a voltage converter for producing a reference signal by converting the level of the output of said pilot generator.
Claim 7
Dependent Claim
31 words
The ground fault detecting apparatus as defined in claim 3, wherein said input means is a voltage detector for converting the input terminal voltage of said load to a reference signal.
Claim 8
Independent Claim
105 words
An apparatus for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply (2) to a load via a transformer, said apparatus comprising input means for producing a voltage signal related to the state of said load, and relay means for indicating occurrence of a ground fault in said power system when the zero phase sequence current in said system is greater than said voltage signal: wherein said transformer has a winding open at one side of the delta connection thereof in such a manner as to detect the zero phase sequence current. (Figs. 6, 7)
Claim 9
Independent Claim
105 words
An apparatus for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply (2) to a load via a transformer, said apparatus comprising input means for producing a voltage signal related to the state of said load, and relay means for indicating occurrence of a ground fault in said power system when the zero phase sequence current in said system is greater than said voltage signal: wherein said transformer has a winding open at one side of the delta connection thereof in such a manner as to detect the zero phase sequence current. (Figs. 6, 7)
Claim 10
Dependent Claim
37 words
The ground fault detecting apparatus as defined in claim 6, wherein said load consists of a motor, and said input means consists of a pilot generator connected to said motor and producing a voltage signal. (Fig. 6)
Claim 11
Dependent Claim
33 words
The ground fault detecting apparatus as defined in claim 6, wherein said input means is a voltage detector for converting the input terminal voltage of said load to a reference signal. (Fig. 7)
Claim 12
Independent Claim
149 words
An apparatus for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply (2) to a load via a transformer, said apparatus comprising first input means (IND3) for detecting the voltage value of the zero phase sequence current in said power system, second input means (IND4) for detecting the frequency of the zero phase sequence current in said power system, arithmetic means (DV) for calculating the ratio between the output of said second input means and the output of said first input means, and discriminating means for indicating occurrence of a ground fault in said power system when the output ratio of said arithmetic means is greater than a predetermined value; wherein said transformer has a winding open at one side of the delta connection thereof in such a manner as to detect the zero phase sequence current. (Fig. 8)
Claim 13
Independent Claim
149 words
An apparatus for detecting a ground fault in a power system which furnishes an electric power from a variable-voltage variable-frequency power supply (2) to a load via a transformer, said apparatus comprising first input means (IND3) for detecting the voltage value of the zero phase sequence current in said power system, second input means (IND4) for detecting the frequency of the zero phase sequence current in said power system, arithmetic means (DV) for calculating the ratio between the output of said second input means and the output of said first input means, and discriminating means for indicating occurrence of a ground fault in said power system when the output ratio of said arithmetic means is greater than a predetermined value; wherein said transformer has a winding open at one side of the delta connection thereof in such a manner as to detect the zero phase sequence current. (Fig. 8)
References Cited (Backward Citations)
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