ABB Relion 670 Series Technical Reference Manual page 142

Section 5
Differential protection
136
In breaker-and-a-half arrangements, there are two local currents meaning two 64 kbit/s
channels to each remote substation. Alternatively, it is possible to add together the two
local currents before sending them and in that way reduce the number of
communication channels needed. This is achieved by selecting proper setting for
parameter TransmCurr (CT-SUM, CT-DIFF1 or CT-DIFF2). However, information
about bias currents is reduced if the alternative option is followed. For further
information and discussions on this matter, refer to the Application manual.
The communication can be arranged as a master-master system or a master-slave
system alternatively. Figure
Here current samples are exchanged between all IEDs, and an evaluation is made in
each IED. This means that a 64 kbit/s communication channel is needed between every
IED included in the same line differential protection zone.
IED
IED
ANSI05000292 V2 EN
Figure 56: 5–terminal line with master-master system
In the master-slave system, current samples are sent from all slave IEDs to one master
IED where the evaluation is made and trip signals are sent to the remote ends when
needed. In this system, a 64 kbit/s communication channel is only needed between the
master, and each one of the slave IEDs, as shown in figure 57.
IED
Comm. Channels
IED
ANSI05000291 V2 EN
Figure 57: 5–terminal line with master-slave system
56 shows a master-master system for a five-terminal line.
Protected zone
IED
Protected zone
IED
1MRK505222-UUS C
IED
Comm. Channels
IED
ANSI05000292_2_en.vsd
IED
IED
ANSI05000291_2_en.vsd
Technical reference manual