CHAPTER 5: SETTINGS GROUPED ELEMENTS
F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 5-239
5
Figure 5-126: Neutral time overcurrent 1 logic
5.7.4.3 Neutral instantaneous overcurrent (ANSI 50N, IEC PIOC)
SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) NEUTRAL CURRENT NEUTRAL IOC1(12)
The neutral instantaneous overcurrent element can 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
phasor 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:
I
op
= 3 x (|I_0| - K x |I_1|) where K = 1/16 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
NEUTRAL IOC1
NEUTRAL IOC1
FUNCTION: Disabled
Range: Disabled, Enabled
NEUTRAL IOC1 SIGNAL
SOURCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
NEUTRAL IOC1
PICKUP: 1.000 pu
Range: 0.020 to 30.000 pu in steps of 0.001
NEUTRAL IOC1 PICKUP
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
NEUTRAL IOC1 RESET
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
NEUTRAL IOC1 BLOCK:
Off
Range: FlexLogic operand
NEUTRAL IOC1
TARGET: Self-reset
Range: Self-reset, Latched, Disabled
NEUTRAL IOC1
EVENTS: Disabled
Range: Disabled, Enabled
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