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. 10, 1989
Filed:
Apr. 21, 1986
David R Aubrey, Saughall, GB;
Ian Jameson, Wirral, GB;
The Electricity Council, London, GB;
Abstract
Excess currents due to faults in an electrical power system are generally larger than excess currents due to the magnetization of distribution transformers. Discrimination has hitherto relied on a threshold detector. Magnetizing currents are, however, asymmetrical, whereas fault currents are symmetrical. A detector detects symmetrical current waveforms on a conductor 1 and thus discriminates between a fault and a magnetizing excess current. A resistor 4, placed across the output terminals of a bridge rectifier 3 has a resistance selected so that the voltage across it exceeds the breakdown voltage of trigger diodes 7 and 8 when the current in conductor 1, in any half cycle, exceeds a desired maximum. Capacitors 13 and 14 will thus only both charge up in response to an excessive symmetrical current. A logic control 23 is connected via lines 21 and 22 to detect such a condition.