Protective relay capable of protection applications without...

Details Protective relay capable of protection applications without... Protective relay capable of protection applications without...

2006-10-17

2006-10-17

Jackson, Stephen W. (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

Feeder protection in distribution networks

C361S064000

Reexamination Certificate

active

07123459

ABSTRACT:
The current differential relay operates without adjustable settings, and includes a phase current differential element with a predetermined threshold, responsive to local phase current values and remote phase current values, to detect three-phase faults and producing a first output signal if the threshold value is exceeded. Either a negative sequence current differential element or two phase current differential elements, also having predetermined threshold values and responsive to the local and remote phase currents, detect phase-to-phase faults and phase-to-phase-to-ground faults and produces a second output signal if the predetermined threshold is exceeded. A negative sequence or zero sequence current differential current element, with a predetermined threshold value is responsive to the local and remote phase currents to detect phase-to-ground faults and to produce a third output signal if the threshold is exceeded. If any one of the first, second and third output signals occurs, a trip signal is generated and directed to the associated circuit breaker. The thresholds are selected to permit use of the relay in a wide range of possible applications.

REFERENCES:
patent: 4538196 (1985-08-01), Sun et al.
patent: 4795983 (1989-01-01), Crockett et al.
patent: 4896241 (1990-01-01), Li et al.
patent: 5793750 (1998-08-01), Schweitzer et al.

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