Apparatus for detecting arcing faults and ground faults in multiwire branch electric power circuits
First Claim
1. Apparatus for detecting faults in multiwire branch circuits including a first line conductor and a second line conductor fed by separate phases or a single center tapped phase, and a common neutral conductor, said apparatus comprising:
- a two pole circuit breaker having a first pole connected to interrupt current in said first line conductor, and a second pole connected to interrupt current in said second line conductor simultaneously with interruption of current in said first line conductor when tripped; and
fault detection circuitry including a first arc fault detector connected to detect arc currents in said first line conductor and generate a first trip signal in response thereto, a second arc fault detector connected to detect arc currents in said second line conductor and generate a second trip signal in response thereto, a ground fault detector connected to detect ground faults in each of said first line conductor and second line conductor and generate a third trip signal in response thereto, and means responsive to each of said first trip signal, said second trip signal and said third trip signal to trip said two pole circuit breaker, and comprising a common trip circuit and means electrically isolating said first trip signal, said second trip signal and said third trip signal from each other.
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Accused Products
Abstract
A multiwire branch circuit including two line conductors and a grounded, common neutral conductor is protected by a two pole circuit breaker connected to interrupt current flow in the two ungrounded line conductors. Three separate protection circuits provide arc fault protection for each of the ungrounded line conductors and ground fault protection for all three conductors. The arc fault detectors use the bimetal of the thermal-magnetic trip device for the associated line conductor, and therefore, are individually referenced to the associated line voltage. Hence, the outputs of the arc fault detectors are electrically isolated from each other and from the output of the ground fault detector, but operate a common trip circuit to open the two pole circuit breaker. The arc fault detectors have separate isolated power supplies. The ground fault detector is powered by a supply which is energized if either of the ungrounded line conductors is energized.
105 Citations
15 Claims
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1. Apparatus for detecting faults in multiwire branch circuits including a first line conductor and a second line conductor fed by separate phases or a single center tapped phase, and a common neutral conductor, said apparatus comprising:
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a two pole circuit breaker having a first pole connected to interrupt current in said first line conductor, and a second pole connected to interrupt current in said second line conductor simultaneously with interruption of current in said first line conductor when tripped; and fault detection circuitry including a first arc fault detector connected to detect arc currents in said first line conductor and generate a first trip signal in response thereto, a second arc fault detector connected to detect arc currents in said second line conductor and generate a second trip signal in response thereto, a ground fault detector connected to detect ground faults in each of said first line conductor and second line conductor and generate a third trip signal in response thereto, and means responsive to each of said first trip signal, said second trip signal and said third trip signal to trip said two pole circuit breaker, and comprising a common trip circuit and means electrically isolating said first trip signal, said second trip signal and said third trip signal from each other. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Apparatus for detecting faults in multiwire branch circuits including a first line conductor and a second line conductor fed by separate phases or a single centertapped phase, and a common neutral conductor, said apparatus comprising:
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a two pole circuit breaker having a first pole connected to interrupt current in said first line conductor, and a second pole connected to interrupt current in said second line conductor simultaneously with interruption of current in said first line conductor when tripped; and fault detection circuitry including; a first arc fault detector connected to detect arc currents in said first line conductor and generate a first trip signal in response thereto and including a first known impedance in series with said first line conductor, means monitoring a first voltage across said first known impedance as a measure of current in said first line conductor and means referencing said first voltage to said first conductor; a second arc fault detector connected to detect arc currents in said second line conductor and generate a second trip signal in response thereto and including a second known impedance connected in series with said second line conductor, means monitoring a second voltage across said second known impedance as a indication of current in said second line conductor and means referencing said second voltage to said second line conductor; a ground fault detector connected to detect line to ground faults in each of said first line conductor and second line conductor and neutral to ground faults and generating a third trip signal in response thereto and powered by a ground fault power supply supplied by each of said first line conductor and second line conductor; and means responsive to each of said first trip signal, said second trip signal and said third trip signal to trip said two pole circuit breaker. - View Dependent Claims (12, 13)
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14. Apparatus for detecting faults in multiwire branch circuits including a first line conductor and a second line conductor fed by separate phases or a single center-tapped phase, and a common neutral conductor, said apparatus comprising:
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a two pole circuit breaker having a first pole connected to interrupt current in said first line conductor, and a second pole connected to interrupt current in said second line conductor simultaneously with interruption of current in said first line conductor when tripped; and fault detection circuitry including; a first arc fault detector connected to detect arc currents in said first line conductor and generate a first trip signal in response thereto and including a first known impedance in series with said first line conductor, means monitoring a first voltage across said first known impedance as a measure of current in said first line conductor and means referencing said first voltage to said first conductor; a second arc fault detector connected to detect arc currents in said second line conductor and generate a second trip signal in response thereto and including a second known impedance connected in series with said second line conductor, means monitoring a second voltage across said second known impedance as a indication of current in said second line conductor and means referencing said second voltage to said second line conductor; a ground fault detector connected to detect ground faults in each of said first line conductor and second line conductor and generate a third trip signal in response thereto; and means responsive to each of said first trip signal, said second trip signal and said third trip signal to trip said two pole circuit breaker. - View Dependent Claims (15)
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Specification