CHAPTER 5: SETTINGS GROUPED ELEMENTSC70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL 5-17555.7.4.4 Neutral directional overcurrent (ANSI 67N, IEC PDEF/PTOC)SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) NEUTRAL CURRENT NEUTRAL DIRECTIONAL OC1The neutral directional overcurrent element provides both forward and reverse fault direction indications for the NEUTRAL DIROC1 FWD and NEUTRAL DIR OC1 REV operands, respectively. The output operand is asserted if the magnitude of the operatingcurrent 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 currentcalculated from the phase currents or the ground current. There are separate pickup settings for the forward-looking andreverse-looking functions. If set to use the calculated 3I_0, the element applies a positive-sequence restraint for betterperformance: a small user-programmable portion of the positive-sequence current magnitude is subtracted from thezero-sequence current magnitude when forming the operating quantity.Eq. 5-16The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious zero-sequence currentsresulting 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 NEUTRAL DIRECTIONAL OC1 NEUTRAL DIR OC1FUNCTION: DisabledRange: Disabled, Enabled NEUTRAL DIR OC1SOURCE: SRC 1Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6 NEUTRAL DIR OC1POLARIZING: VoltageRange: Voltage, Current, Dual, Dual-V, Dual-I NEUTRAL DIR OC1 POLVOLT: Calculated V0Range: Calculated V0, Aux. Voltage (VX) NEUTRAL DIR OC1 OPCURR: Calculated 3I0Range: Calculated 3I0, Measured IG NEUTRAL DIR OC1 POS-SEQ RESTRAINT: 0.063Range: 0.000 to 0.500 in steps of 0.001 NEUTRAL DIR OC1OFFSET: 0.00 ΩRange: 0.00 to 250.00 Ω in steps of 0.01 NEUTRAL DIR OC1 FWDECA: 75° LagRange: –90 to 90° in steps of 1 NEUTRAL DIR OC1 FWDLIMIT ANGLE: 90°Range: 40 to 90° in steps of 1 NEUTRAL DIR OC1 FWDPICKUP: 0.050 puRange: 0.006 to 30.000 pu in steps of 0.001 NEUTRAL DIR OC1 REVLIMIT ANGLE: 90°Range: 40 to 90° in steps of 1 NEUTRAL DIR OC1 REVPICKUP: 0.050 puRange: 0.006 to 30.000 pu in steps of 0.001 NEUTRAL DIR OC1 BLK:OffRange: FlexLogic operand NEUTRAL DIR OC1TARGET: Self-resetRange: Self-reset, Latched, Disabled NEUTRAL DIR OC1EVENTS: DisabledRange: Disabled, EnabledI op 3 I_0 K I_1×–( )×=
