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2.8 Earth Fault Protection in Earthed Systems (optional)
219
7SD5 Manual
C53000-G1176-C169-1
The earth fault protection can also be blocked during the single-pole dead time of an
automatic reclose cycle. This prevents an incorrect measurement resulting from the
zero sequence current and voltage signals arising in this state. The blocking affects
the entire protection function and is maintained for approximately 40ms after reclosure
to prevent signal race conditions. It is issued as fault indication
„E/F BLOCK“
(No.
1332).
If the device is combined with an external automatic reclose device or if single-pole
tripping can result from a separate (parallel tripping) protection device, the earth fault
protection must be blocked via binary input during the single-pole open condition.
Switching Onto an
Earth Fault The line energization detection can be used to achieve quick tripping when energizing
the circuit breaker in case of an earth fault. The earth fault protection can then trip
three-pole without delay. Parameters can be set to determine for which stage(s) the
non-delayed tripping following energization apply (see also logic diagrams from Figure
2-88 to Figure 2-92).
The non-delayed tripping in case of line energization detection is blocked as long as
the inrush-stabilization recognizes a rush current. This prevents instantaneous trip-
ping by a stage which, under normal conditions, is sufficiently delayed during energi-
zation of a transformer.
2.8.2 Setting Notes
General During the configuration of the device scope of functions (refer to Section 2.1.1,
address
131 Earth Fault O/C
) it was determined which group of characteristics is
to be available. Only those parameters that apply to the available characteristics, ac-
cording to the selected configuration and the version of the device, are accessible in
the procedures described below.
Parameter
3101 FCT EarthFltO/C
can be used to switch the earth fault protection
ON
or
OFF
. This refers to all stages of the earth fault protection.
If not required, each of the four stages can be deactivated by setting its
MODE...
to
Inactive
(see below).
Blocking The earth fault protection can be blocked by the distance protection to give preference
to the selective fault clearance by the distance protection over tripping by the earth
fault protection. In setting address
3102 BLOCK for Dist.
it is determined whether
blocking is carried out during each fault detection of the distance protection (
every
PICKUP
) or only during single-phase fault detection by the distance protection
(
1phase PICKUP
) or only during multiple-phase fault detection by the distance pro-
tection (
multiph. PICKUP
). If blocking is desired, set
NO
.
It is also possible to block the earth fault protection trip only for pickup of the distance
protection on the protected line section. To block the earth fault protection for faults
occurring within zone Z1, set address
3174 BLK for DisZone
to
in zone Z1
. To
block the earth fault protection for faults occurring within zone Z1 or Z1B, set address
3174 BLK for DisZone
to
in zone Z1/Z1B
. If, however, blocking of the earth
fault protection by the distance protection is to take effect regardless of the fault loca-
tion, set address
3174 BLK for DisZone
to
in each zone
.
Address
3102
thus refers to the fault type and address
3174
to the fault location. The
two blocking options create an AND condition. To block the earth fault protection only
for single-phase faults occurring within zone Z1, set address
3102 BLOCK for
Dist.
=
1phase PICKUP
and
3174 BLK for DisZone
=
in zone Z1
. To block
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