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:
Feb. 22, 2000
Filed:
Oct. 17, 1997
Applicant:
Inventors:
Armando Guzman-Casillas, Pullman, WA (US);
Jeffrey B Roberts, Pullman, WA (US);
Assignee:
Schweitzer Engineering Laboratories, Inc., Pullman, WA (US);
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H02H / ;
U.S. Cl.
CPC ...
361 89 ; 361 80 ; 361 65 ; 361115 ;
Abstract
The system impedance ratio (SIR) is determined for the original zone 1 distance element reach of a protective relay. The reduction in the original zone 1 reach is then determined, using the SIR value and a known table of reduced values. When a fault is recognized the minimum reach to just detect the fault is determined. A trip signal is provided without any delay if the minimum reach is less than or equal to the reduced reach. The trip is delayed for a selected time if the minimum reach is greater than the reduced reach but not greater than the original reach.