Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific quantity comparison means
Patent
1987-11-12
1989-10-10
Pellinen, A. D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific quantity comparison means
361 87, H02H 316
Patent
active
048736023
ABSTRACT:
A circuit for preventing the generation of an erroneous output signal from a protective relay for detecting faults in a three phase alternating current electrical power distribution system, which relay uses a full wave rectified signal as an operate quantity. The circuit includes a band pass filter having an input adapted to receive the full wave rectified signal; a center frequency which is tuned to the frequency of at least one principal harmonic component of the full wave rectified signal; a gain substantially equal to -1; and an output. A two-input summing amplifier has one input which is adapted to receive the full wave rectified signal and the other input which is connected to the output of the band pass filter. In the preferred embodiment, the circuit removes the second harmonic component of the full wave rectified signal thereby preventing the relay from generating a faulty trip signal for those faults beyond the reach of the relay which, but for the elimination of the increase in the magnitude of the DC level of the operate signal due to the contribution of the second harmonic component, would cause the relay to operate.
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General Electric Company
Murray William H.
Pellinen A. D.
Policinski Henry J.
Wysocki A. Jonathan
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