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STATIC INSTANTANEOUS OVERCURRENT RELAY WITH LOW TRANSIENT OVERREACH
STATIC INSTANTANEOUS OVERCURRENT RELAY WITH LOW TRANSIENT OVERREACH
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机译：低瞬态过电流的静态瞬时过电流继电器
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摘要
11RCO 4392STATIC INSTANTANEOUS OVERCURRENT RELAY WITHLOW TRANSIENT OVERREACHABSTRACT OF THE DISCLOSUREA static instantaneous overcurrent relay withreduced transient overreach is provided for use inprotecting an a-c power line from overcurrents. Therelay operates on an input signal representative of themagnitude of the current in the a-c power line anddevelops a relay output signal when the magnitude of thecurrent reaches a predetermined magnitude. In a preferredembodiment, the relay includes a level detector circuitfor receiving the input signal which is in the form of apulsating waveform having the same frequency as the a-cpower line. The level detector circuit develops a discretelevel detector output signal in response to each pulse ofthe waveform which attains a magnitude representative ofthe predetermined magnitude. Output circuit means iscoupled to receive the discrete level detector outputsignals and includes temporary inhibit means for inhibitingthe development of the relay output signal until theoutput circuit has received two of the discrete leveldetector signals. In one form of the invention, thetemporary inhibit means includes delay circuit means forreceiving the discrete level detector output signals anddeveloping a delayed signal. AND circuit means is thenprovided to receive the discrete level detector outputsignals and the delayed signal resulting in a relayoutput signal after two level detector output signals arepresent. In one form of the present invention, the relayhas a transient overreach percentage of less than 8% forpower line angles up to 75°. The relay of the presentinvention may be employed in connection with a singlephase input signal as well as with a three phase inputsignal.
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