5-180 C60 Breaker Protection System GE Multilin5.6 GROUPED ELEMENTS 5 SETTINGS5c) NEUTRAL INSTANTANEOUS OVERCURRENT (ANSI 50N, IEC PIOC)PATH: SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) NEUTRAL CURRENT NEUTRAL IOC1(8)The neutral instantaneous overcurrent element may be used as an instantaneous function with no intentional delay or as adefinite time function. The element essentially responds to the magnitude of a neutral current fundamental frequency pha-sor calculated from the phase currents. A positive-sequence restraint is applied for better performance. A small portion(6.25%) of the positive-sequence current magnitude is subtracted from the zero-sequence current magnitude when formingthe operating quantity of the element as follows:(EQ 5.16)The 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 faultsThe positive-sequence restraint must be considered when testing for pickup accuracy and response time (multiple ofpickup). The operating quantity depends on how test currents are injected into the relay (single-phase injection):(EQ 5.17) NEUTRAL IOC1NEUTRAL IOC1FUNCTION: DisabledRange: Disabled, EnabledMESSAGE NEUTRAL IOC1 SIGNALSOURCE: SRC 1Range: SRC 1, SRC 2, SRC 3, SRC 4MESSAGE NEUTRAL IOC1PICKUP: 1.000 puRange: 0.000 to 30.000 pu in steps of 0.001MESSAGE NEUTRAL IOC1 PICKUPDELAY: 0.00 sRange: 0.00 to 600.00 s in steps of 0.01MESSAGE NEUTRAL IOC1 RESETDELAY: 0.00 sRange: 0.00 to 600.00 s in steps of 0.01MESSAGE NEUTRAL IOC1 BLOCK:OffRange: FlexLogic operandMESSAGE NEUTRAL IOC1TARGET: Self-resetRange: Self-reset, Latched, DisabledMESSAGE NEUTRAL IOC1EVENTS: DisabledRange: Disabled, EnabledI op 3 I_0 Kx I_1–( )×= where K 1 16⁄=I op13--- 3 K–( )× x I injected=
