GE 745 TRANSFORMER MANAGEMENT RELAY

GE Power Management 745 Transformer Management Relay 7-1
7 SCHEME LOGIC 7.1 INTRODUCTION
7
7 SCHEME LOGIC 7.1 INTRODUCTION 7.1.1 DESCRIPTION
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.
7.1.2 SETPOINTS
• 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
7.1.3 MEASUREMENT UNITS
• 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.
7.1.4 TIME DELAYS
• shown as a block with the following schematic symbol:
• the delay before pickup is indicated by t
PKP
, and the delay after dropout is indicated by t
DO
.
• if the delay before pickup is adjustable, the associated delay setpoint is shown directly above, and the
schematic symbol indicates that t
PKP
= DELAY.
7.1.5 LED INDICATORS
• shown as the following schematic symbol:
⊗
• the exact wording of the front panel label identifies the indicator
7.1.6 LOGIC
• described using basic ‘AND’ gates and 'OR' gates
The remainder of this chapter illustrates the block diagrams for each feature.
t
PKP
=DELAY
t
DO
=0