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:
Jul. 08, 2003
Filed:
Jun. 29, 2001
Jeffrey B. Roberts, Viola, ID (US);
Schweitzer Engineering Laboratories, Inc., Pullman, WA (US);
Abstract
In a three terminal power line current differential protection system, all three phase current values (I , I and I ) are obtained from all three terminals. The current values for each phase are processed in three successive processing operations, using in turn the current values from each terminal as local current values and the combination of the other two terminal current values in each case as the remote current values. The resulting local and remote current values are then processed against preselected values which establish a restrain region in the current ratio (alpha) plane. Current values for each set of local and combined remote currents which result in the ratio being within the restrain region result in a blocking signal while current values which result in a ratio outside of the region result in a tripping signal. If the outputs of the three processing operations agree, then that signal is the system output. If there is disagreement, the output produced when the terminal having the largest current (Imax) value is the local current is the system output.