Operating instructions7SV512
V1
79C53000---G1176---C91
In those cases where the pre-conditions of one or
the other plausibility check cannot be fulfilled be-
cause of the physical arrangement of the substation
components (e.g. ifthe earth current of the feeder is
not available), reaction of some plausibility checks
can be matched to the physical connection in ad-
dresses 1221 to 1223.
If, for example, the assignment of the binary inputs
andtriprelays hasbeen changed forsome reason, it
may be necessary to avoid blocking of the breaker
failure protection by the current summation monitor
or the hard-ware supervision, in address 1221.
In order to bridge out transient phenomena during
which the plausibility conditions are violated for
short time periods (e.g. the current sum condition
during current transformer saturation), the blocking
of the breaker failure protection can be delayed un-
der address 1222.
One important plausibility check of the breaker fail-
ure protection isthe 2-out-of-4condition onthe pick-
upof the current detectors. But this can onlyoperate
if all three phase currents and the residual (earth)
current are introduced to the relay. If this four-cur-
rent-connection is not possible forexternal reasons,
the breaker failure protection function itself calcu-
lates the negative sequence current from the phase
currents and uses this as the fourth criterion in the
2-out-of-4 check. If the earth current is not con-
nected to the relay, address 2123 PLAUS 1POLe
must be set to NEG.SEQ. CURRENT. Otherwise cur-
rent detection would not be possible!
1 2 2 1 B L O C K M O N
Y E S
N O
Pick-up of the current sum monitor or hard-ware moni-
tor blocks the breaker failure protection
YES or
NO
Delay time for blocking of the breaker failure protec-
tion when the current sum monitor or the hard-ware
monitor has picked up (provided address 1221 is set
to YES)
Smallest setting value: 0.05 s
Largest setting value: 32.00 s
or 1, i.e. no blocking
1 2 2 2 T - B L O C K M O N
5 . 0 0 s
1 2 2 3 P L A U S 1 P O L
R E S I D U A L C U R R E N T
N E G . S E Q . C U R R E N T
Plausibility check for single-phase current detection is
performed with the
RESIDUAL CURRENT i.e. the earth current con-
nected to the relay terminals or
NEGative SEQuence CURRENT which is calculated
from the phase currents
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