GE D60 Instruction Manual page 491
Line distance protection system
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- Instruction manual (490 pages)
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CHAPTER 5: SETTINGS
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
; three-phase injection, opposite rotation: I
op
injected
5.7.11.4 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
D60 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
NEG SEQ IOC1 PICKUP
DELAY: 0.00 s
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
op
Figure 5-155: 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
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
= I
).
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
GROUPED ELEMENTS
Eq. 5-22
5
5-277
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