GE C70 Instruction Manual page 299

CHAPTER 5: SETTINGS
5.7.4.4 Neutral directional overcurrent (ANSI 67N, IEC PDEF/PTOC)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  NEUTRAL CURRENT  NEUTRAL DIRECTIONAL OC1
 NEUTRAL
 DIRECTIONAL OC1
The neutral directional overcurrent element provides both forward and reverse fault direction indications for the
and
OC1 FWD NEUTRAL DIR OC1 REV
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 either the neutral current
calculated from the phase currents or the ground current. There are separate pickup settings for the forward-looking and
reverse-looking functions. If set to use the calculated 3I_0, the element applies a positive-sequence restraint for better
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
• Transformation errors of current transformers (CTs) during double-line and three-phase faults
• Switch-off transients during double-line and three-phase faults
C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL
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
operands, respectively. The output operand is asserted if the magnitude of the operating
× (
I = 3 I_0
op
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
Range: Voltage, Current, Dual, Dual-V, Dual-I
Range: Calculated V0, Aux. Voltage (VX)
Range: Calculated 3I0, Measured IG
Range: 0.000 to 0.500 in steps of 0.001
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: 0.006 to 30.000 pu in steps of 0.001
Range: 40 to 90° in steps of 1
Range: 0.006 to 30.000 pu in steps of 0.001
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
× )
K I_1
–
GROUPED ELEMENTS
5
NEUTRAL DIR
Eq. 5-16
5-175