Blocking Scheme; Delta Blocking Scheme - ABB RED650 Technical Manual

Section 13
Scheme communication
13.1.6.1
13.1.6.2
404
on a received signal for a fast trip, so its dependability is lower than that of a

blocking scheme.

Blocking scheme
The principle of operation for a blocking scheme is that an overreaching zone is
allowed to trip instantaneously after the settable co-ordination time tCoord has
elapsed, when no signal is received from the remote IED.
The received signal, which shall be connected to CR, is used to block the zone to
be accelerated to clear the fault instantaneously (after time tCoord). The forward
overreaching zone to be accelerated is connected to the input CACC, see
figure 193.
In case of external faults, the blocking signal (CR) must be received before the
settable timer tCoord elapses to prevent a false trip, see figure 193.
The function can be totally blocked by activating the input BLOCK. Tripping can
be blocked by activating the input BLKTR. Signal send can be blocked by
activating the input BLKCS.
CACC
AND
CR
IEC05000512 V1 EN-US
Figure 193: Basic logic for trip signal in blocking scheme
Channels for communication in each direction must be available.

Delta blocking scheme

In order to avoid delays due to carrier coordination times, the initiation of sending
of blocking signal to remote end is done by a fault inception detection element
based on delta quantities of currents and voltages. The delta based fault detection is
very fast and if the channel is fast there is no need for delaying the operation of the
remote distance element. The received blocking signal arrives well before the
distance element has started. If the fault is in forward direction the sending is
immediately stopped by a forward directed distance, directional current or
directional earth fault element.
The fault inception detection element detects instantaneous changes in any phase
currents or zero sequence current in combination with a change in the
corresponding phase voltage or zero sequence voltage. The criterion for the fault
inception detection is if the change of any phase voltage and current exceeds the
settings DeltaU and DeltaI respectively, or if the change of zero sequence voltage
and zero sequence current exceeds the settings Delta3U0,Delta3I0 respectively.
The schemeType is selected as DeltaBlocking.
tCoord
t
TRIP
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Line differential protection RED650 2.2 IEC
Technical manual
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