GE L90 Instruction Manual page 211

5 SETTINGS
d) NEUTRAL DIRECTIONAL OVERCURRENT (ANSI 67N)
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PATH: SETTINGS GROUPED ELEMENTS
# NEUTRAL
# DIRECTIONAL OC1
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There are two Neutral Directional Overcurrent protection elements available. The element provides both forward and
reverse fault direction indications the
operand is asserted if the magnitude of the operating current is above a pickup level (overcurrent unit) and the fault direc-
tion is seen as "forward or "reverse", respectively (directional unit).
The overcurrent unit responds to the magnitude of a fundamental frequency phasor of the either the neutral current calcu-
lated from the phase currents or the ground current. There are two separate pickup settings for the forward- and reverse-
looking functions, respectively. If set to use the calculated 3I_0, the element applies a "positive-sequence restraint" for bet-
ter performance: a small user-programmable portion of the positive–sequence current magnitude is subtracted from the
zero-sequence current magnitude when forming the operating quantity.
The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious zero-sequence currents
resulting from:
• System unbalances under heavy load conditions.
GE Multilin
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SETTING GROUP 1(6) NEUTRAL CURRENT
NEUTRAL DIR OC1
FUNCTION: Disabled
NEUTRAL DIR OC1
SOURCE: SRC 1
NEUTRAL DIR OC1
POLARIZING: Voltage
NEUTRAL DIR OC1 POL
VOLT: Calculated V0
NEUTRAL DIR OC1 OP
CURR: Calculated 3I0
NEUTRAL DIR OC1 POS-
SEQ RESTRAINT: 0.063
NEUTRAL DIR OC1
OFFSET: 0.00 Ω
NEUTRAL DIR OC1 FWD
ECA: 75° Lag
NEUTRAL DIR OC1 FWD
LIMIT ANGLE: 90°
NEUTRAL DIR OC1 FWD
PICKUP: 0.050 pu
NEUTRAL DIR OC1 REV
LIMIT ANGLE: 90°
NEUTRAL DIR OC1 REV
PICKUP: 0.050 pu
NEUTRAL DIR OC1 BLK:
Off
NEUTRAL DIR OC1
TARGET: Self-reset
NEUTRAL DIR OC1
EVENTS: Disabled
and
NEUTRAL DIR OC1 FWD NEUTRAL DIR OC1 REV
× ( ×
I 3 I_0 K I_1
= –
op
L90 Line Differential Relay
5.5 GROUPED ELEMENTS
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NEUTRAL DIRECTIONAL OC1(2)
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: Voltage, Current, Dual
Range: Calculated V0, Measured VX
Range: Calculated 3I0, Measured IG
Range: 0.000 to 0.500 in steps of 0.001
Ω
Range: 0.00 to 250.00 in steps of 0.01
Range: –90 to 90° in steps of 1
Range: 40 to 90° in steps of 1
Range: 0.002 to 30.000 pu in steps of 0.001
Range: 40 to 90° in steps of 1
Range: 0.002 to 30.000 pu in steps of 0.001
Range: FlexLogic™ operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
operands, respectively. The output
)
5
(EQ 5.17)
5-121