GE Multilin
750/760 Feeder Management Relay
5-45
5 SETPOINTS
5.6 S5 PROTECTION
5
d) NEUTRAL DIRECTIONAL
PATH: SETPOINTS
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S5 PROTECTION
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NEUTRAL CURRENT
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NEUTRAL DIRECTIONAL
The Neutral Directional feature controls the operation of all neutral overcurrent elements and allows them to discriminate
between forward or reverse faults. Refer to Phase Directional OC on page 5–39 for more details on directional principles.
Neutral directional can be either voltage, current, or dual polarized. The calculated neutral current is always the operating
current.
When voltage polarized, the polarizing quantity is the zero sequence voltage which is calculated from the bus input volt-
ages. The VT Connection Type must be wye in this case. If the polarizing voltage drops below the
MIN OPERATING VOLTAGE
value, the direction defaults to forward. The following table shows the operating current and polarizing voltage used for neu-
tral directional control
On relays with bootware revision 3.00 or newer, the polarizing current is input via the Ground CT input. Otherwise,
the polarizing current is input via a dedicated polarizing CT input. See Section 3.2.3: Current Inputs on page 3–8 for
additional details.
When current polarized the Ground CT Input (Terminals G10 and H10) is used to determine neutral current direction. The
polarizing current comes from a source CT measuring the current flowing from the ground return into the neutral of a
ground fault current source which is usually a transformer. The direction is Forward when the neutral current is within ±90°
of the polarizing current. Otherwise, the direction is Reverse. If the polarizing current is less than 5% of CT nominal then the
direction defaults to forward.
Dual polarization provides maximum security and reliability. If the polarizing voltage magnitude is insufficient then current
polarizing takes control. If the polarizing current magnitude is insufficient then the voltage polarizing takes control. If neither
voltage nor current polarizing is possible then the direction defaults to forward.
NEUTRAL DIRECTIONAL
[ENTER] for more
NEUTRAL DIRECTIONAL
FUNCTION: Disabled
Range: Disabled, Alarm, Latched Alarm, Control
NEUTRAL DIRECTIONAL
RELAYS (3-7): -----
Range: Any combination of 3 to 7 Auxiliary relays
NEUTRAL POLARIZING
Voltage
Range: Voltage, Current, Dual
NEUTRAL DIRECTIONAL
MTA: 315° Lead
Range: 0 to 359° Lead in steps of 1
MIN POLARIZING
VOLTAGE: 0.05 x VT
Range: 0.00 to 1.25 x VT in steps of 0.01
Table 5–12: NEUTRAL DIRECTIONAL CHARACTERISTICS
QUANTITY
OPERATING
CURRENT
POLARIZING VOLTAGE
(VT CONNECTION = WYE)
POLARIZING CURRENT
Neutral
3
I
o
=
I
a
+
I
b
+
I
c
–
V
o
= –(
V
a
+
V
b
+
V
c
) / 3
I
g
(see note below)
ENTER
ESCAPE
ð
ð
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
N
OTE