GE C60 Instruction Manual page 372

GROUPED ELEMENTS
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
5
• 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):
NEUTRAL IOC1 FUNCTION
NEUTRAL IOC1 SIGNAL SOURCE
element.
NEUTRAL IOC1 PICKUP
NEUTRAL IOC1 PICKUP DELAY
coordination with other elements and relays.
NEUTRAL IOC1 RESET DELAY
between the operate output state and the return to logic 0 after the input passes outside the defined pickup range. This
setting is used to ensure that the relay output contacts are closed long enough to ensure reception by downstream
equipment.
NEUTRAL IOC1 BLOCK
overcurrent element.
NEUTRAL IOC1 EVENTS
sequence of events recorder.
5-204
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
— This setting enables and disables the neutral instantaneous overcurrent protection element.
— This setting selects the signal source for the neutral instantaneous overcurrent protection
— This setting specifies the neutral instantaneous overcurrent pickup level in per-unit values.
— This setting delays the assertion of the
— This setting specifies a delay for the reset of the neutral instantaneous overcurrent element
— Assertion of the operand assigned to this setting blocks operation of the neutral instantaneous
— This setting enables and disables the logging of neutral instantaneous overcurrent events in the
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
operands. It is used to achieve timing
NEUTRAL IOC OP
C60 BREAKER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
Eq. 5-16
Eq. 5-17