Method of operation7SV512
V1
33C53000---G1176---C91
4.2.4.4 Combined initiation conditions
The conditions of initiation and circuit breaker pole
monitoring can be combined at will. Figure 4.13
shows the total logic.
The essential components of the total logic are ex-
plained inthe foregoing subsections. Inaddition, the
figure shows interlocking of the phase segregated
stages by the common phase stage: If a three-pole
trip occurred by the main protection, only the time
stage for three-pole trip shall operate, the phase-
segregated stages are blocked.
4.2.4.5 Function examples
Assuming an overhead line feeder where single-
pole auto-reclose is used. The three phase segre-
gated trip commands of the short-circuit protection
are then fed to the three binary inputs (refer Figure
4.11) ”>Trip L1”, ”>Trip L2”, and ”>Trip L3”,
the general fault detection signal to the input
”>Start”. If available , the earth fault detection sig-
nal is connected to ”>Start N”. The 2-out-of-4 log-
ic produces the (internal) signals ”Init L1”, ”Init L2”,
and ”Init L3”, and/or ”Init L123”.
Current flow is monitored according Figure 4.4. As
long as the current flow criterion of the associated
phase isfulfilled, the time T1---1POLE (Figure 4.12or
4.13) continues in case of single-pole trip: in case of
three-pole trip the time T1---3POLE continues as
long as either of the current flow criteria (Figure 4.4)
is fulfilled (Figure 4.10 or 4.13).
As soon as the breaker (pole) has opened the cur-
rent flow criteria disappear very fast, and all func-
tions reset to the quiescent state.
If the current(s) have not been interrupted until expi-
ry of the time T1---POLE or T1---3POLE, trip com-
mand ”BFP Trip L*” (for the associated pole *)
Figure 4.12 or 4.13), or ”BFP Trip L123” (three-
pole) (Figure 4.10 or 4.13), is generated. This com-
mand trips e.g. a second (set of)trip coilofthe feed-
er circuit breaker. At the same time the second time
stage T2---CURRENT starts.
If current flow is even recognized after expiry of
T2---CURRENT, bus-bar trip command ”BFB Trip
BB”is generated (Figure 4.10or 4.12or 4.13), which
will isolate the bus-bar (section).
Assuming a transformer feeder. The trip command
oftheshort-circuit protection isthen fedto the binary
input ”>Trip 3pole”, the fault detection signal to
”>Start” (Figure 4.11). If the short-circuit protec-
tion does not provide a fault detection signal (e.g.
differential protection), its trip signal is connected to
both mentioned binary inputs.
Current flow is monitored according Figure 4.4. As
long as the current flow criterion is fulfilled foratleast
onephase, thetime T1---3POLE (Figure 4.10or4.13)
continues running.
As soon as the breaker has opened the current flow
criteria disappear veryfast, and all functions reset to
the quiescent state.
If not all currents have been interrupted until expiry
of the time T1---3 POLE, trip command ”BFP Trip
L123” (Figure 4.10 or 4.13) is generated. This com-
mand trips e.g. asecond trip coil ofthe feeder circuit
breaker. At the same time the second time stage
T2---CURRENT starts.
If current flow is even recognized after expiry of
T2---CURRENT, bus-bar trip command ”BFP Trip
BB”is generated (Figure 4.10or4.14), which will iso-
late the bus-bar (section).
The trip command of the Buchholz protection is
equally fed to the binary input ”>Trip 3pole” (Fig-
ure 4.10 or 4.13). In order to ensure dual channel
control of initiation of the breaker failure protection,
the same Buchholz trip command is fed also to the
input ”>Start”.
Trip command ofthe Buchholz protection isnotnec-
essarily combined with a detectable current flow.
The breaker failure protection automatically recog-
nizes when current flow is not a reliable criterion for
thereaction ofthe circuitbreaker and will switchover
to breaker auxiliary contact monitoring (Figure 4.7
and 4.6). The time T1---3POLE (Figure 4.10 or 4.13)
continues running as long as at least one circuit
breaker auxiliary contact is closed (Parallel connec-
tion of the auxiliary contact).
As soon as all three breaker poles have opened, the
auxiliary contact criterion disappears, and all func-
tions reset to the quiescent state.
Ifnotallthree breaker poles have opened untilexpiry
of the time T1---3POLE, trip command ”BFP Trip
L123” (Figure 4.10 or 4.13) is generated. This com-
mand trips e.g. asecond trip coil ofthe feeder circuit
breaker. At the same time the second time stage
T2---CB---AUX starts.
If not all three circuit breaker poles have opened
even after expiry of T2---CB---AUX, bus-bar trip com-
mand ”BFP Trip BB” is generated (Figure 4.10 or
4.13), which will isolate the bus-bar (section).
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