GE UR Series Instruction Manual page 178

5.5 GROUPED ELEMENTS
c) NEUTRAL DIRECTIONAL OC1 / OC2 (NEUTRAL DIRECTIONAL OVERCURRENT: ANSI 67N)
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PATH: SETTINGS GROUPED ELEMENTS
„
NEUTRAL
„
DIRECTIONAL OC1
5
There are two Neutral Directional Overcurrent protection elements available. The element provides both forward and
reverse fault direction indications the NEUTRAL DIR OC1 FWD and NEUTRAL DIR OC1 REV operands, respectively. The
output operand is asserted if the magnitude of the operating current is above a pickup level (overcurrent unit) and the fault
direction 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 portion (6.25%) of the positive–sequence current magnitude is subtracted from the zero-sequence
current magnitude when forming the operating quantity.
× (
I 3 I_0
= –
op
The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious zero-sequence currents
resulting from:
• System unbalances under heavy load conditions.
• Transformation errors of Current Transformers (CTs) during double-line and three-phase faults.
• Switch-off transients during double-line and three-phase faults.
5-94
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SETTING GROUP 1(8)
NEUTRAL DIR OC1
FUNCTION: Disabled
NEUTRAL DIR OC1
MESSAGE
SOURCE: SRC 1
NEUTRAL DIR OC1
MESSAGE
POLARIZING: Voltage
NEUTRAL DIR OC1 POL
MESSAGE
VOLT: Calculated V0
NEUTRAL DIR OC1 OP
MESSAGE
CURR: Calculated 3I0
NEUTRAL DIR OC1
MESSAGE
OFFSET: 0.00 Ω
NEUTRAL DIR OC1 FWD
MESSAGE
ECA: 75° Lag
NEUTRAL DIR OC1 FWD
MESSAGE
LIMIT ANGLE: 90°
NEUTRAL DIR OC1 FWD
MESSAGE
PICKUP: 0.050 pu
NEUTRAL DIR OC1 REV
MESSAGE
LIMIT ANGLE: 90°
NEUTRAL DIR OC1 REV
MESSAGE
PICKUP: 0.050 pu
NEUTRAL DIR OC1 BLK:
MESSAGE
Off
NEUTRAL DIR OC1
MESSAGE
TARGET: Self-reset
NEUTRAL DIR OC1
MESSAGE
EVENTS: Disabled
× )
K I_1 , where K is 1/16.
L90 Line Differential Relay
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NEUTRAL CURRENT NEUTRAL DIRECTIONAL OC1
Range: Disabled, Enabled
Range: SRC 1, SRC 2,..., SRC 6
Range: Voltage, Current, Dual
Range: Calculated V0, Measured VX
Range: Calculated 3I0, Measured IG
Range: 0.00 to 250.00 Ω 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
5 SETTINGS
GE Power Management