faults. Inadequate speed or dependability can cause delayed tripping for internal faults
or even unwanted operations.
This scheme may use virtually any communication media that is not adversely affected
by electrical interference from fault generated noise or by electrical phenomena, such
as lightning, that cause faults. Communication media that uses metallic path are
particularly subjected to this type of interference, therefore, they must be properly
shielded or otherwise designed to provide an adequate communication signal during
power system faults. At the permissive overreaching scheme, the carrier 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 zone1 can be prolonged. To secure correct
operations of current reversal logic in case of parallel lines, when applied, the carrier
send signal CS shall not be prolonged. So set the
tSendMin
to zero in this case. There is
no need to delay the trip at receive of the carrier signal, so set the timer
tCoord
to zero.
Unblocking scheme
SEMOD141790-46 v2
Unblocking scheme cannot be used at ZC1PPSCH (85) as a failure of the
communication channel cannot give any information about which phase/phases have a
fault.
16.2.2.3
Intertrip scheme
SEMOD141790-49 v2
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 (CCRBRF, 50BF).
In intertrip scheme, the carrier 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 sending of signals, the timer
tCoord
should be set to
10-30 ms dependant on type and security of the communication channel.
The general requirement for teleprotection equipment operating in intertripping
applications is that it should be very secure and very dependable, since both inadequate
security and dependability may cause unwanted operation. In some applications the
equipment shall be able to receive while transmitting, and commands may be
transmitted over longer time period than for other teleprotection systems.
16.2.3
Setting guidelines
SEMOD141796-1 v1
SEMOD141800-4 v2
The parameters for the Phase segregated scheme communication logic for distance
protection function ZC1PPSCH (85) are set via the local HMI or PCM600.
Section 16
1MRK 504 163-UUS A
Scheme communication
824
Transformer protection RET670 2.2 ANSI
Application manual
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