Intertrip Scheme - ABB Relion REC670 Applications Manual

1MRK 511 358-UEN A
At the permissive overreaching scheme, the send signal (CS) might be issued in parallel both
from an overreaching zone and an underreaching, independent tripping zone. The CS signal
from the overreaching zone must not be prolonged while the CS signal from zone 1 can be
prolonged.
To secure correct operations of current reversal logic in case of parallel lines, when applied, the
send signal CS shall not be prolonged. So set the
There is no need to delay the trip at receipt of the signal, so set the timer
OR
B
OR
IEC09000014 V1 EN-US
Figure 173: Principle of Permissive overreaching scheme
OR: Overreaching
CR: Communication signal received
CS: Communication signal send
T2: Timer step 2
Unblocking scheme
Metallic communication paths adversely affected by fault generated noise may not be suitable
for conventional permissive schemes that rely on signal transmitted during a protected line
fault. With power line carrier, for example, the communication signal may be attenuated by the
fault, especially when the fault is close to the line end, thereby disabling the communication
channel.
To overcome the lower dependability in permissive schemes, an unblocking function can be
used. Use this function at older, less reliable, power-line carrier (PLC) communication, where
the signal has to be sent through the primary fault. The unblocking function uses a guard
signal CRG, which must always be present, even when no CR signal is received. The absence of
the CRG signal during the security time is used as a CR signal. This also enables a permissive
scheme to operate when the line fault blocks the signal transmission. Set the
ms.
14.1.2.4

Intertrip scheme

In some power system applications, there is a need to trip the remote end breaker
immediately from local protections. This applies, for instance, when transformers or reactors
are connected to the system without circuit-breakers or for remote tripping following
operation of breaker failure protection.
In intertrip scheme, the send signal is initiated by an underreaching zone or from an external
protection (transformer or reactor protection). At remote end, the received signals initiate a
trip without any further protection criteria. To limit the risk for unwanted trip due to spurious
Application manual
A
CS
A
A
tSendMin to zero in this case.
B
TRIP = OR + CR OR
B B B ,
IEC09000014-1-en.vsd
Section 14
Scheme communication
tCoord to zero.
OR
A
+ T2
B
M16866-67 v4
tSecurity to 35
M16866-71 v3
345