Description of Operation
GARD 8000 Distance Relay
RFL Electronics Inc.
IA
IB
IC
0
20
A open
52b
B open
C open
1 pole open
3 poles open
Any pole open
Figure 9-29. Open Pole Logic with One Common 52b Input
9.7
CLOSE-INTO-FAULT
The distance relay is provided with a Close-Into-a-Fault Detector, which generates a non-reclosing
three-phase tripping signal when a fault is detected at the time a breaker close command is issued.
Under such conditions, the fault is considered to be inside the line or it would have been cleared by the
corresponding protection elements. This element will activate after a manual breaker closing operation:
1.
After activation of the status contact input Manual Close signal, in case of a fault inside
zone 2 or zone 3 (according to setting selection for ‘CIFT supervision zone’).
2.
Following reclosing, in case of a fault inside zone 2 or zone 3 (according to setting
selection for ‘CIFT supervision zone’) and when “Z1 ext after recl” is enabled.
3.
Following closing (manual or reclose) for a positive sequence voltage below 50 V and
current over the set value for ‘CIFT overcurrent pickup.’
The settings for the CIFT function are on page “Power Swing Block and other Advanced Functions.
The overcurrent function provides a means to clear a fault when a distance measurement is not possible
due to a lack of adequate polarization voltage, when the PTs are connected on the line side and closing
into a 3 phase fault. The use of Zone 2/3 when possible (two and single phase faults) enables a higher
overcurrent setting for the current element as only 3 phase faults need to be considered which increases
security. In addition, the current elements used for Close-Into-Fault have a settable 2
nd
harmonic
restraint.
August 1, 2009
9-31
973.334.3100
