GE F60 Instruction Manual page 402

GROUPED ELEMENTS
The negative-sequence instantaneous overcurrent element can be used as an instantaneous function with no intentional
delay or as a definite time function. The element responds to the negative-sequence current fundamental frequency
phasor magnitude (calculated from the phase currents) and applies a positive-sequence restraint for better performance:
a small portion (12.5%) of the positive-sequence current magnitude is subtracted from the negative-sequence current
magnitude when forming the operating quantity.
The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious negative-sequence
currents resulting from
• System unbalances under heavy load conditions
• Transformation errors of current transformers (CTs) during three-phase faults
• Fault inception and switch-off transients during 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 the test currents are injected into the relay (single-phase injection:
I = 0.2917 x I
5
op injected
5.7.8.4 Negative sequence directional overcurrent (ANSI 67Q, IEC PDEF/PTOC)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  NEGATIVE SEQUENCE CURRENT  NEG SEQ DIR
OC1(2)
 NEG SEQ DIR OC1

5-228
NEG SEQ IOC1 RESET

DELAY: 0.00 s
NEG SEQ IOC1 BLOCK:

Off
NEG SEQ IOC1

TARGET: Self-reset
NEG SEQ IOC1

EVENTS: Disabled
I = |I_2| - K x |I_1| where K = 1/8
op
; three-phase injection, opposite rotation: I
Figure 5-118: Negative sequence IOC1 logic
NEG SEQ DIR OC1

FUNCTION: Disabled
NEG SEQ DIR OC1

SOURCE: SRC 1
NEG SEQ DIR OC1

OFFSET: 0.00 Ω
NEG SEQ DIR OC1

TYPE: Neg Sequence
Range: 0.00 to 600.00 s in steps of 0.01
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
= I ).
op injected
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 0.00 to 250.00 ohms in steps of 0.01
Range: Neg Sequence, Zero Sequence
F60 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
Eq. 5-27