GE Multilin
745 Transformer Management Relay
5-53
5 SETPOINTS
5.6 S4 ELEMENTS
5
FLEXCURVES™:
The custom FlexCurve™ is described in Section 5.4.6: FlexCurves™ on page 5–33. The curve shapes for the Flex-
Curves™ are derived from the formula:
(EQ 5.9)
where:
T
= Operate Time (sec.),
M
= Multiplier Setting,
I
= Input Current, and
I
pickup
= Pickup Current setpoint
DEFINITE TIME CURVE:
The Definite Time curve shape operates as soon as the pickup level is exceeded for a specified period of time. The base
definite time curve delay is 0.1 seconds. The curve multiplier makes this delay adjustable from 0.000 (instantaneous) to
10.000 seconds.
c) WINDING 1(3) PHASE TIME OVERCURRENT
PATH: SETPOINTS
ÖØ
S4 ELEMENTS
ÖØ
PHASE OC
Ö
W1(3) PHASE TIME OC
•
W1(3) PHASE TIME OC PICKUP
: Enter the phase current level (in units of relay nominal current) above which the
Winding 1(3) Phase Time Overcurrent element will pickup and start timing.
•
W1(3) PHASE TIME OC SHAPE
: Select the time overcurrent curve shape to use for the Winging 1(3) Phase Time
Overcurrent. Time Overcurrent Curves on page 5–49 describes the TOC curve shapes.
•
W1(3) PHASE TIME OC MULTIPLIER
: Enter the multiplier constant by which the selected time overcurrent curve
shape (the base curve) is to be shifted in time.
•
W1(3) PHASE TIME OC RESET
: 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(3) HARMONIC DERATING CORRECTION
: Select “Enabled” to enable automatic harmonic derating correction of
the Winging 1(3) Phase Time Overcurrent curve. The 745 calculates the derated transformer capability when supplying
non-sinusoidal load currents (as per ANSI / IEEE C57.110-1986) and, when this feature is enabled, automatically shifts
the phase time overcurrent curve pickup in order to maintain the required protection margin with respect to the trans-
former thermal damage curve, as illustrated below.
W1 PHASE TIME OC
[ENTER] for more
W1 PHASE TIME OC
FUNCTION: Enabled
Range: Enabled, Disabled
W1 PHASE TIME OC
TARGET: Latched
Range: Self-Reset, Latched, None
W1 PHASE TIME OC
PICKUP: 1.20 x CT
Range: 0.05 to 20.00 x CT in steps of 0.01
W1 PHASE TIME OC
SHAPE: Ext Inverse
Range: see description below
W1 PHASE TIME OC
MULTIPLIER: 1.00
Range: 0.00 to 100.00 in steps of 0.01
W1 PHASE TIME OC
RESET: Linear
Range: Instantaneous, Linear
W1 PHASE TIME OC
BLOCK: Disabled
Range: Logc Inpt 1 to 16, Virt Inpt 1 to 16, Output Rly 2 to
8, SelfTest Rly, Vir Outpt 1 to 5, Disabled
W1 HARMONIC DERATING
CORRECTION: Disabled
Range: Logic Input 1 to 16, Disabled
T
M
FlexcurveTime at
I
I
pickup
----------------
×
when
I
I
pickup
----------------
1.00
≥
=
ENTER
ESCAPE
ð
ð
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE