GE G30 Instruction Manual page 436

GROUPED ELEMENTS
5.7.5.3 Neutral instantaneous overcurrent (ANSI 50N, IEC PIOC)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  NEUTRAL CURRENT  NEUTRAL IOC1
 NEUTRAL IOC1

5
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:
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
5-222
Figure 5-112: Neutral time overcurrent 1 logic
NEUTRAL IOC1

FUNCTION: Disabled
NEUTRAL IOC1 SIGNAL

SOURCE: SRC 1
NEUTRAL IOC1

PICKUP: 1.000 pu
NEUTRAL IOC1 PICKUP

DELAY: 0.00 s
NEUTRAL IOC1 RESET

DELAY: 0.00 s
NEUTRAL IOC1 BLOCK:

Off
NEUTRAL IOC1

TARGET: Self-reset
NEUTRAL IOC1

EVENTS: Disabled
I = 3 x (|I_0| - K x |I_1|) where K = 1/16
op
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 0.020 to 30.000 pu in steps of 0.001
Range: 0.00 to 600.00 s in steps of 0.01
Range: 0.00 to 600.00 s in steps of 0.01
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
Eq. 5-39