Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1996-03-05
1997-05-06
DeBoer, Todd
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361 64, 361 96, H02H 308
Patent
active
056277164
ABSTRACT:
A microprocessor based overcurrent trip unit includes an analog circuit for monitoring phase currents in the electrical interrupting device. The analog circuit is adapted to interface with the microprocessor over a range of selectable setpoints for instantaneous tripping and at the same time accurately monitor the phase currents even during a condition when the current sensing transformers are saturated. The overcurrent trip unit also allows the function of the long time delay characteristics of protection curve to be varied in order to provide better coordination with the characteristics of other overcurrent tripping devices in an electrical distribution system, such as a current limiting fuse, thereby enhancing the overall reliability of the system. For example, the function may be varied to provide either a fixed or FLAT, It, I.sup.2 t and I.sup.4 t functions. The overcurrent tripping device also allows for relatively wide adjustment ranges for the long time delay and short time delay protection portions of an overcurrent protection curve. In order to prevent any overlapping of the protection ranges, the long time delay portion is prevented from tripping the interrupting device prior to the short time delay portion.
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ETAP Brochure by Operation Technology, Inc., pp. 1-18, undated.
Engel Joseph C.
Lagree James L.
Tomeo Anthony
Wargo Harry W.
DeBoer Todd
Eaton Corporation
Moran Martin J.
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