Setting Guidelines - ABB REB670 Applications Manual

Section 17
Remote communication
17.1.3
458
Typical LDCM communication delay between two IEDs is in order of 30-40 ms. Note that
for disconnector status this delay will not pose any practical problems. However, time
delay caused by LDCM communication can be crucial for circuit breakers status. In such
cases it is strongly recommended that at least the circuit breaker closing command from
every circuit breaker is directly wired to all three phases/IEDs to minimize any risk for
unwanted operation of the busbar differential protection zones due to late inclusion of
respective bay current into the differential measuring circuit.

Setting guidelines

ChannelMode: This parameter can be set Normal or Blocked. Besides this, it can be set
OutOfService which signifies that the local LDCM is out of service. Thus, with this
setting, the communication channel is active and a message is sent to the remote IED that
the local IED is out of service, but there is no COMFAIL signal and the analog and binary
values are sent as zero.
TerminalNo: This setting shall be used to assign an unique address to each LDCM, in all
current differential IEDs. Up to 256 LDCMs can be assigned a unique number. Consider
a local IED with two LDCMs:
• LDCM for slot 302: Set TerminalNo to 1 and RemoteTermNo to 2
• LDCM for slot 303: Set TerminalNo to 3 and RemoteTermNo to 4
In multiterminal current differential applications, with 4 LDCMs in each IED, up to 20
unique addresses must be set.
The unique address is necessary to give high security against incorrect
addressing in the communication system. Using the same number for
setting TerminalNo in some of the LDCMs, a loop-back test in the
communication system can give incorrect trip.
RemoteTermNo: This setting assigns a number to each related LDCM in the remote IED.
For each LDCM, the parameter RemoteTermNo shall be set to a different value than
parameter TerminalNo, but equal to the TerminalNo of the remote end LDCM. In the
remote IED the TerminalNo and RemoteTermNo settings are reversed as follows:
• LDCM for slot 302: Set TerminalNo to 2 and RemoteTermNo to 1
• LDCM for slot 303: Set TerminalNo to 4 and RemoteTermNo to 3
The redundant channel is always configured in the lower position, for
example
1MRK 505 337-UUS -
Application manual