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:
Sep. 08, 1998
Filed:
Dec. 13, 1996
Yi Hu, Cary, NC (US);
David Hart, Raleigh, NC (US);
Damir Novosel, Cary, NC (US);
Robert Smith, Cary, NC (US);
ABB Power T&D Company Inc., Raleigh, NC (US);
Abstract
A system for implementing accurate V/Hz value measurement and trip time determination for generator/transformer overexcitation protection independent of the conventional frequency tracking and phasor estimation based on Discrete Fourier Transformation (DFT) techniques. The half-cycle summation technique of the invention is a non-recursive digital technique which measures the per unit V/Hz value by summing the sampled data points in every half cycle of a sinusoidal input signal and dividing the sum with the ideal base sum value. When the input voltage signal is sampled at a reasonable frequency, the technique of the invention approximates the accurate per unit V/Hz value of the input voltage signal and thus obtains an accurate V/Hz characteristic directly without computing voltage and frequency separately.