Relay device and corresponding method

Electricity: electrical systems and devices – Safety and protection of systems and devices – Feeder protection in distribution networks

Reexamination Certificate

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Details

C361S063000, C361S064000, C361S065000, C361S066000, C361S067000, C361S068000, C361S080000, C361S081000, C361S082000, C361S084000

Reexamination Certificate

active

07599161

ABSTRACT:
A method of operating a relay device, in an electrical circuit comprising first and second main circuit breakers, and a bus tie circuit breaker connecting the first and second main circuit breakers, the method comprising computing a first positive sequence current phasor for the first main circuit breaker and a second positive sequence current phasor for the second main circuit breaker computing a first positive sequence voltage phasor for the first main circuit breaker and a second positive sequence voltage phasor for the second main circuit breaker; computing a correction of the first positive sequence voltage and second positive sequence voltage to a line-to-neutral phase angle reference if there is any rotation in a potential transformer connection; determining a fault has occurred when a magnitude of a current through at least one of the first main circuit breaker or the second main circuit breaker exceeds a predetermined threshold; determining a phase angle difference by comparing the phase angle of the positive sequence current phasor with the phase angle of the positive sequence voltage phasor for both the first main circuit breaker or the second main circuit breaker having the magnitude of current determined to have exceeded the predetermined level; and determining the fault is located upstream or downstream of the first main circuit breaker or the second main circuit breaker having the magnitude of current determined to have exceeded the predetermined level, if the phase angle difference is determined to be above a predetermined amount.

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U.S. Appl. No. 11/618,175, filed Dec. 29, 2006, William Premerlani et al.
“The Single-Processor Concept for Protection and Control of Circuit Breakers in Low-Voltage Switchgear”, M Valdes, T Papallo & I Purkayastha, IEEE Transactions Jul./Aug.
“IEEE Guide for Performing Arc-Flash Hazard Calculations”, IEEE Standard 1584-2002, Published by The Institute of Electrical and Electronic Engineers, Inc. NY, NY.
“IEEE Guide for Performing Arc-Flash Hazard Calculations-Amendment 1” IEEE Standard 1584a-2204, Published by the Institute of Electrical and Electronic Engineers, Inc. NY, NY.

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