Quotient differential protection for electric power delivery systems
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorsBogdan Z. Kasztenny, Eugeniusz Rosolowski
Life of this patent
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Abstract
Quotient differential protection of electric power delivery system equipment is described herein. Load-side currents and source-side currents are used without need of tap changer and control switch positions of the dual-core phase-shifting transformer being protected. The quotient differential signal is determined based on comparing the winding turn ratios in individual transformer phases, resulting in a differential signal that includes the products of currents. Similarly, the restraining signal comprises the products of currents.
Claims21
A protection system for detecting internal faults in dual-core phase shifting transformers comprising,
- a signal acquisition subsystem to obtain source-side and load-side currents
- a differential protection element in communications with the signal acquisition subsystem configured to:
- compare winding turn ratios between multiple phases of the transformer wherein the winding turn ratios are determined using the source-side and load-side currents;
- and,
- issue a trip command when the comparison indicates that the winding turn ratios differ between the phases.
A protection system for detecting faults in the dual-core phase-shifting transformer comprising:
- a signal acquisition subsystem configured to acquire a plurality of source-side current signals from source-side terminals of the dual-core phase-shifting transformer and load-side current signals from load-side terminals of the dual-core phase-shifting transformer for each phase;
- a differential protection element in communication with the signal acquisition subsystem, configured to:
- calculate a quotient differential signal as a product of currents selected from the source-side and load-side current signals;
- calculate a quotient restraining signal as a product of currents selected from the source-side and load-side current signals;
- and
- determine a fault condition using the calculated quotient differential and quotient restraining signals;
- and,
- a protective action subsystem in communication with the differential protection element, configured to effect a protective action upon determination of the fault condition.
A system for differential protection of a multi-phase electric power delivery system equipment that introduces a first current ratio and a second current ratio;
- comprising:
- a signal acquisition subsystem configured to acquire a plurality of source-side current signals from each phase of the multi-phase electric power delivery system equipment and load-side current signals each phase of the multi-phase electric power delivery system equipment;
- a differential protection element in communication with the signal acquisition subsystem, configured to:
- calculate a quotient differential signal as a product of currents selected from the source-side and load-side current signals;
- calculate a quotient restraining signal as a product of currents selected from the source-side and load-side current signals;
- and
- determine a fault condition using the calculated quotient differential and quotient restraining signals;
- wherein the quotient differential signal is determined as a balance between:
- a first quotient of current signals for a first loop of the multi-phase electric power delivery system equipment;
- and
- a second quotient of current signals for a second loop of the multi-phase electric power delivery system equipment;
- that each equal a product of the first ratio and the second ratio under healthy conditions;
- and,
- a protective action subsystem in communication with the differential protection element, configured to effect a protective action upon determination of the fault condition.
A differential protection element for a multi-phase electric power delivery system, comprising:
- a first input to receive first-side currents from a protected portion of the electric power delivery system;
- a second input to receive second-side currents from a protected portion of the electric power delivery system, wherein the first-side currents and the second-side currents are related through a first turn ratio and a second turn ratio;
- a differential signal module to calculate a balance signal from the first-side currents and the second-side currents, wherein the balance signal accounts for the first ratio and the second ratio and the balance signal is calculated independent of the first ratio and the second ratio;
- and
- a protective action subsystem in communication with the differential protection element, configured to effect a protective action upon the balance signal exceeding a predetermined threshold.
Dependencies are inferred from the claim text.