Apparatus for insuring the security of output signals from protective relays used in electric power systems
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorEdmund O. Schweitzer, III
Life of this patent
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Abstract
In a protective relay (10), which contains a microprocessor (30), for monitoring a power transmission line, an output enable decoder (72) and a one-shot timer (74) produce a very short (5 microsecond) signal in response to an address signal from the microprocessor. The output from the timer is applied as one input to AND gate (70). A conventional address decoder, responsive to an address signal identifying a particular output port from the microprocessor, provides another output to AND gate (70). AND gate (70) produces a latch control signal when the two signals are coincident in time. The latch control signal enables the particular output port to receive instructions from a data bus (60).
Claims10
An apparatus for insuring the correct assertion of output signals by a protective relay used in a power transmission system, comprising:
- output port decoder means in a protective relay which includes a microprocessor and which is used in a power transmission system, said output port decoder means, in response to address information from the microprocessor, producing an address signal identifying a particular output port of the relay;
- an enable decoder assembly in the protective relay responsive to an address enable signal from the microprocessor to produce an output enable signal for a selected period of time;
- and
- means responsive to the coincidence in time of the output enable signal an the address signal to produce a control signal which is applied to said particular output port to enable said particular output port to receive instructions from the microprocessor.
Dependencies are inferred from the claim text.