GE D60 Instruction Manual page 419

CHAPTER 5: SETTINGS
— Assertion of the operand assigned to this setting blocks operation of the neutral time overcurrent
NEUTRAL TOC1 BLOCK
element.
— This setting enables and disables the logging of neutral time overcurrent events in the sequence
NEUTRAL TOC1 EVENTS
of events recorder.
5.7.8.3 Neutral instantaneous overcurrent (ANSI 50N, IEC PIOC)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  NEUTRAL CURRENT  NEUTRAL IOC1(6)
 NEUTRAL IOC1

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
D60 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 5-134: 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
GROUPED ELEMENTS
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
5
Eq. 5-16
5-241