Electrical transmission or interconnection systems – Plural load circuit systems – Common conductor or return type
Reexamination Certificate
2005-07-22
2008-09-16
Sherry, Michael J (Department: 2836)
Electrical transmission or interconnection systems
Plural load circuit systems
Common conductor or return type
Reexamination Certificate
active
07425778
ABSTRACT:
Provided is an apparatus and method for providing to a differential relay an operational vector-group compensation setting pair that automatically provides correction for a phase shift occurring between currents of at least two windings of a power transformer. The method includes calculating a first and second plurality of phasors using secondary currents derived from respective first and second winding of the at least two windings. The method also includes selecting one pair of vector-group compensation settings based on operate current values calculated using different pair combinations of the vector-group compensation settings applied to the first and second plurality of phasors. The method further includes comparing phase angles of like-phase phasors to determine if the phase angles are within a pre-determined angle range, and enabling application of the selected pair of vector-group compensation settings as the operational vector-group compensation setting pair if the phase angles are within the pre-determined angle range.
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Mike Young, John Horak, “Commissioning Numerical Relays,” Basler Electric Company, Highland Illinois USA.
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Fischer Normann
Labuschagne Casper
Amrany Adi
Eugene M. Cummings, P.C.
Schweitzer Engineering Laboratories Inc.
Sherry Michael J
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