Negative sequence directional element for a relay useful in protecting power transmission lines
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorsJeffrey B. Roberts, Edmund O. Schweitzer, III
Life of this patent
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Abstract
A directional element measures the negative sequence voltage and the negative sequence current and from those quantities produces a scalar quantity related to the negative sequence impedance of a power transmission line relative to the location of the directional element. The scalar quantity is then compared against two threshold quantity settings, one to determine a forward fault, the other to determine a reverse fault. The scalar quantity must be less than the forward threshold quantity for a forward fault and greater than the reverse threshold quantity for a reverse fault.
Claims10
A directional element for use in a relay for protection of power transmission lines, comprising:
- means for obtaining negative sequence voltage and current quantities of the power signal present on the power transmission line;
- means for calculating from said negative sequence voltage and current quantities a quantity which is representative of the negative sequence impedance of the transmission line;
- and
- means for comparing said calculated quantity against first and second selected threshold quantities to identify direction of a fault relative to the relay, the first threshold quantity being for a forward fault and the second threshold quantity being for a reverse fault.
Dependencies are inferred from the claim text.