Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Patent
1975-12-22
1977-03-29
Britton, Howard W.
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
325320, 325434, 325430, 325402, 325 2, 340167A, H04B 116
Patent
active
040152065
ABSTRACT:
A receiver is provided for utilization in a protective relaying modem to effectively distinguish between two mutually exclusive signal frequencies in a given frequency channel and which are respectively indicative of a "fault" or "no-fault" condition in a remote power transmission line. The received signals are coupled to a channel detector which utilizes a local oscillator and mixers to translate the received signal down in frequency so that simple low pass filters can isolate the desired frequency channel. The outputs of the low pass filters are operated on by a combination of multipliers and differentiators to generate an AM related output and a FM related output. The FM signal output of the channel detector is DC in nature and has an amplitude proportional to the deviation of the received signal frequency from the center frequency of the channel. This signal is used by separation circuitry to ascertain a fault or no-fault condition. The AM output is a DC signal that is proportional to the strength of the received signal and is analyzed to determine if the originally received signal was generated or unacceptably affected by electronic noise. If the noise content does not fall within the predeterminably set limits, any "fault" condition signal is automatically inhibited until the validity of such signal can be ascertained. The detection time for ascertaining whether a valid fault signal has been received can be adjusted to achieve a minimum yet effective detection time. The output of the receiver indicating a fault condition can be utilized to control various circuit breakers in the power transmission system.
REFERENCES:
patent: 2715677 (1955-08-01), Turner
patent: 2955199 (1960-10-01), Mindes
patent: 3641438 (1972-02-01), Canty
patent: 3671939 (1972-06-01), Trimble
patent: 3895187 (1975-07-01), Antoszewski
Britton Howard W.
Chin Tommy P.
Gilbert Douglas M.
GTE Lenkurt (Canada) Ltd.
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