Ground Overcurrent; Winding 1 (2/3) Ground Time Overcurrent - GE 745 TRANSFORMER MANAGEMENT RELAY Instruction Manual

5 SETPOINTS
In the 745, "ground" refers to the current measured in a CT in the connection between the transformer neutral
and ground. The 745 has two ground inputs which are automatically assigned to wye or zig-zag connected
windings, based on the transformer type selected. As a result, only those ground overcurrent settings whose
winding is assigned a ground input are displayed and enabled. This section contains the settings to configure
the ground overcurrent elements. Included are ground time overcurrents for each (wye or zig-zag) winding,
and two levels of ground instantaneous overcurrent for each (wye or zig-zag) winding.
S GROUND OC
S [ENTER] for more
a) WINDING 1 (2/3) GROUND TIME OVERCURRENT
S W1 GND TIME OC
S [ENTER] for more
W1 GROUND TIME OC
FUNCTION: Enabled
W1 GROUND TIME OC
TARGET: Latched
W1 GROUND TIME OC
PICKUP: 0.85 x CT
W1 GROUND TIME OC
SHAPE: Ext Inverse
W1 GROUND TIME OC
MULTIPLIER: 1.00
W1 GROUND TIME OC
RESET: Linear
W1 GROUND TIME OC
BLOCK: Disabled
GE Power Management
This message indicates the start of the GROUND OVERCURRENT section. To
continue with these setpoints press
next section.
Here is the start of the GROUND TIME OVERCURRENT section for Winding 1 (2/
3). To continue with these setpoints press
the next section.
Range: Disabled / Enabled
Range: Self-reset / Latched / None
Select None to inhibit the display of the target message when the element
operates. Thus an element whose "target type" is None never disables the
LED self-test feature since it cannot generate a displayable target message.
Range: 0.05 to 20.00 (steps of 0.01)
Enter the level of ground current (in units of relay nominal current) above
which the W1 (2/3) ground time overcurrent element will pickup and start
timing.
Range: Ext Inverse / Very Inverse / Norm Inverse / Mod Inverse / Definite
Time / IEC Curve A / IEC Curve B / IEC Curve C / IEC Short Inv /
IAC Ext Inv / IAC Very Inv / IAC Inverse / IAC Short Inv / FlexCurve
A / FlexCurve B / FlexCurve C
Select the time overcurrent curve shape to be used for the W1 (2/3) ground
time overcurrent element. Section 5.9: TIME OVERCURRENT CURVES on
page 5–91 describes the time overcurrent curve shapes.
Range: 0.00 to 100.00 (steps of 0.01)
Enter the multiplier constant by which the selected time overcurrent curve
shape (the base curve) is to be shifted in time.
Range: Instantaneous / Linear
Select Linear reset to coordinate with electromechanical time overcurrent
relays, in which the reset characteristic (when the current falls below the
reset threshold before tripping) is proportional to ratio of energy accumulated
to that required to trip. Select Instantaneous reset to coordinate with relays,
such as most static units, with instantaneous reset characteristics.
Range: Disabled / Logc Inpt 1 (2-16) /Virt Inpt 1 (2-16) / Output Rly 1 (2-8) /
SelfTest Rly / Virt Outpt 1 (2-5)
745 Transformer Management Relay
5.6 S4 ELEMENTS

5.6.8 GROUND OVERCURRENT

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