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:
Jan. 23, 2001
Filed:
Jun. 07, 1995
David Train, Framingham, MA (US);
Philip A. von Guggenberg, Cambridge, MA (US);
George A. Cavigelli, Lexington, MA (US);
Doble Engineering Company, Watertown, MA (US);
Abstract
A group of bushings receives voltage in parallel to produce a current output from each bushing. Cumulatively combining the current outputs from the bushings vectorially furnishes a vector sum bushing current. Reference voltage devices also produce reference current outputs. Cumulatively combining the reference current outputs vectorially provides a vector sum reference current, and differentially vectorially combining the vector sum reference current with the vector sum bushing current delayed by 90° provides a difference signal representative of a bushing condition. As an alternative to the reference voltage devices, a second group of bushings may be used. In this case, a delay of 90° is not required. The invention may also be used to monitor the condition of other capacitive devices, for example, high voltage current transformers.