Negative sequence differential element

Details Negative sequence differential element Negative sequence differential element

2011-03-08

2011-03-08

Jackson, Stephen W (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific quantity comparison means

Reexamination Certificate

active

07903381

ABSTRACT:
A negative sequence differential element may detect a fault in an electrical power system by computing a differential between negative sequence values derived from a first phase-current measurement and a second phase-current measurement. A transformer may be disposed between the first phase-current and second phase-current measurement location. The first phase-current measurement and the second phase-current measurement may be normalized and a negative sequence current may be calculated therefrom. The negative sequence currents may be used to calculate an operating quantity, which may be an absolute value of the sum of the first and second negative sequence currents, and a restraint quantity comprising a maximum of the first and second negative sequence currents. The restraint quantity may be scaled by a slope factor. A fault may be detected if the operating quantity exceeds the scaled restraint quantity and a pickup current threshold.

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