The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 24, 1998
Filed:
Jan. 04, 1996
Jeffrey B Roberts, Moscow, ID (US);
Daqing Hou, Pullman, WA (US);
Armando Guzman-Casillas, Pullman, WA (US);
Schweitzer Engineering Laboratories, Inc., Pullman, WA (US);
Abstract
An out-of-step blocking circuit is established with two additional zones in the impedance plane, with the circuit determining the time that the positive sequence impedance takes to move between the two zones. The distance elements for selected zones of protection for the relay are blocked if the impedance moves between the two zones at a rate less than a first threshold. However, a trip signal results if the rate of change is greater than the first threshold but less than a second threshold, indicating an unstable swing. Further, an inner blinder zone is established in the impedance plane within the additional two zones of protection. If the positive sequence impedance entering that zone does not move from that zone within a certain time during an otherwise out-of-step condition, the blocking signals are terminated.