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7 SCHEME LOGIC
7 SCHEME LOGIC 7.1 INTRODUCTION
The 745 instruction manual provides complete descriptions of the operation of each feature in the relay in
Chapter 5: SETPOINTS in the form of written descriptions. This chapter provides block diagrams for each fea-
ture. These diagrams are sequential logic diagrams illustrating how each setpoint, input parameter, and inter-
nal logic is used in a feature to obtain an output.
•
shown as a block with heading 'SETPOINT'
•
the location of setpoints is indicated by the 'Path' heading of the diagram
•
the exact wording of the displayed setpoint message identifies the setpoint
•
major functional setpoint selections are listed below the name and are incorporated in the logic
•
shown as a block with inset labelled 'RUN'
•
the associated pickup or dropout setpoint is shown directly above
•
operation of the detector is controlled by logic entering the 'RUN' inset
•
relationship between setpoint and input parameter is indicated by simple mathematical symbols: '<' (less
than), '>' (greater than), etc.
•
shown as a block with the following schematic symbol:
•
the delay before pickup is indicated by t
•
if the delay before pickup is adjustable, the associated delay setpoint is shown directly above, and the
schematic symbol indicates that t
•
shown as the following schematic symbol:
•
the exact wording of the front panel label identifies the indicator
•
described using basic 'AND' gates and 'OR' gates
The remainder of this chapter illustrates the block diagrams for each feature.
GE Power Management
t
=DELAY
PKP
t
=0
DO
, and the delay after dropout is indicated by t
PKP
= DELAY.
PKP
⊗
745 Transformer Management Relay
7.1 INTRODUCTION
7.1.1 DESCRIPTION
7.1.2 SETPOINTS
7.1.3 MEASUREMENT UNITS
7.1.4 TIME DELAYS
.
DO
7.1.5 LED INDICATORS
7.1.6 LOGIC
7
7-1
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