GE Multilin 750/760 Feeder Management Relay 5-67
5 SETPOINTS 5.6 S5 PROTECTION
5
e) NEUTRAL DISPLACEMENT
PATH: SETPOINTS ÖØ S5 PROTECTION ÖØ VOLTAGE ÖØ NTR DISPLACEMENT
The 750/760 incorporates a Neutral Displacement element, which uses the internally derived 3V
0
value. This protection
element requires the three phase Bus VTs to be wye connected. When setting the pickup level for this element, it is impor-
tant to consider the error in the VT ratio as well as the normal voltage unbalance on the system. The Neutral Displacement
setpoints are as follows.
The same curves used for the time overcurrent elements are used for Neutral Displacement. When using the curve
to determine the operating time of the Neutral Displacement element, substitute the ratio of neutral voltage to the
pickup level for the current ratio shown on the horizontal axis of the curve plot.
Be aware that the neutral displacement feature should be applied with caution. It would normally be applied to give line to
ground fault coverage on high impedance grounded or ungrounded systems, which are isolated. This constraint stems from
the fact that a measurement of 3V
0
cannot discriminate between a faulted circuit and an adjacent healthy circuit. Use of a
time delayed back-up or an alarm mode allow other protections an opportunity to isolate the faulted element first.
Figure 5–31: NEUTRAL DISPLACEMENT LOGIC
NTR DISPLACEMENT
[ENTER] for more
NTR DISPLACEMENT
FUNCTION: Disabled
Range: Disabled, Trip, Alarm, Latched Alarm, Control
NTR DISPLACEMENT
RELAYS (3-7): -----
Range: Any combination of 3 to 7 Auxiliary relays
NTR DISPLACEMENT
PICKUP: 1.00 x VT
Range: 0.00 to 1.25 x VT in steps of 0.01
NTR DISPLACEMENT
CURVE: 2.0 s
Range: see Table 5–4: TOC Curve Selections on page
5–32 for values
NTR DISPLACEMENT
MULTIPLIER: 2.0 s
Range: 0.00 to 100.00 in steps of 0.01
NTR DISPLACEMENT
RESET: Instantaneous
Range: Instantaneous, Linear
ENTER
ESCAPE
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NOTE
Courtesy of NationalSwitchgear.com
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