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:
Apr. 07, 1981
Filed:
Feb. 26, 1979
Applicant:
Inventors:
Allan T Johns, Corsham, GB;
Michael A Martin, Bradford-on-Avon, GB;
Assignee:
National Research Development Corporation, London, GB;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G06F / ; G06F / ; H02H / ;
U.S. Cl.
CPC ...
364482 ; 324 52 ; 361 79 ; 364551 ; 364576 ;
Abstract
An electrical power fault protection relay operates when the calculated impedance of the section of the system it protects shows a sudden change. The instantaneous voltage and current is measured. A calculation device then calculates the Fourier transform of a window of the actual voltage and current over a time interval and of the modified current that would flow if the voltage on each side of the time interval was zero. The actual impedance is calculated from the ratio of the Fourier transforms of the actual voltage and the modified current.