GE C60, Instruction Manual

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5-180 C60 Breaker Protection System GE Multilin
5.6 GROUPED ELEMENTS 5 SETTINGS
5
c) 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 a
definite 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 forming
the operating quantity of the element as follows:
(EQ 5.16)
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
The positive-sequence restraint must be considered when testing for pickup accuracy and response time (multiple of
pickup). The operating quantity depends on how test currents are injected into the relay (single-phase injection):
(EQ 5.17)

NEUTRAL IOC1

NEUTRAL IOC1
FUNCTION: Disabled
Range: Disabled, Enabled
MESSAGE
NEUTRAL IOC1 SIGNAL
SOURCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4
MESSAGE
NEUTRAL IOC1
PICKUP: 1.000 pu
Range: 0.000 to 30.000 pu in steps of 0.001
MESSAGE
NEUTRAL IOC1 PICKUP
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
NEUTRAL IOC1 RESET
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
NEUTRAL IOC1 BLOCK:
Off
Range: FlexLogic operand
MESSAGE
NEUTRAL IOC1
TARGET: Self-reset
Range: Self-reset, Latched, Disabled
MESSAGE
NEUTRAL IOC1
EVENTS: Disabled
Range: Disabled, Enabled
I
op
3 I_0 K x I_1
–
( ) ×
=
where K 1 16 ⁄
=
I
op
1
3
---
3 K
–
( ) × x
I
injected
=