Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Patent
1995-06-06
1997-11-25
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
361 94, H02H 300
Patent
active
056918690
ABSTRACT:
A low cost analog arcing detector and a circuit breaker incorporating such a detector provide a variable response time to arcing faults based upon the amplitude of the arcing current. A filter generates pulses having an amplitude proportional to the amplitude of the step increase in current generated by the striking of the arc. The pulses are rectified and the amount by which the single polarity pulses exceed a threshold value, selected to eliminate nuisance trips on current step increases characteristic of some common loads, is integrated by a capacitor connected to a resistor which continually adjusts the capacitor voltage in a sense opposite to that of the pulses. The capacitor and resistor are selected to generate a trip signal as a function of the accumulated, time attenuated magnitude of the step increases in current associated with each striking of the arc current. Preferably, the pulses are squared before the reference current is subtracted to provide faster response for large amplitude arc currents, while avoiding false trips caused by known loads. Preferably, the arcing detector is used with a ground current detector which provides further protection by tripping on ground currents flowing through carbon tracks deposited by arcing currents below the threshold of the arcing fault detector.
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"Arcing Ground Fault Detection System", Bulletin 1409, Allen-Bradley Co. catalog; undated, pp. 192-193 no date.
Engel Joseph C.
MacKenzie Raymond W.
Eaton Corporation
Gaffin Jeffrey A.
Leja Ronald W.
Moran Martin J.
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