GE 745 TRANSFORMER MANAGEMENT RELAY User Manual

GE Power Management 745 Transformer Management Relay 5-57
5 SETPOINTS 5.6 S4 ELEMENTS
5
5.6.8 GROUND OVERCURRENT
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.
a) WINDING 1 (2/3) GROUND TIME OVERCURRENT
y GROUND OC
y
[ENTER] for more
This message indicates the start of the
GROUND OVERCURRENT
section. To
continue with these setpoints press , or press to go to the
next section.
y W1 GND TIME OC
y
[ENTER] for more
Here is the start of the
GROUND TIME OVERCURRENT
section for Winding 1 (2/
3). To continue with these setpoints press , or press to go to
the next section.
W1 GROUND TIME OC
FUNCTION: Enabled
Range: Disabled / Enabled
W1 GROUND TIME OC
TARGET: Latched
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.
W1 GROUND TIME OC
PICKUP: 0.85 x CT
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.
W1 GROUND TIME OC
SHAPE: Ext Inverse
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.
W1 GROUND TIME OC
MULTIPLIER: 1.00
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.
W1 GROUND TIME OC
RESET: Linear
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.
W1 GROUND TIME OC
BLOCK: Disabled
Range: Disabled / Logc Inpt 1 (2-16) /Virt Inpt 1 (2-16) / Output Rly 1 (2-8) /
SelfTest Rly / Virt Outpt 1 (2-5)
ENTER
MESSAGE
ENTER
MESSAGE

GE 745 TRANSFORMER MANAGEMENT RELAY Specifications

General

Brand	GE
Model	745 TRANSFORMER MANAGEMENT RELAY
Category	Relays
Language	English