IEC15000460-1-en.vsd
IEC15000460 V1 EN-US
Figure 32: Two-end power line with two CB and CT groups at each end
Figure
shows a three-end power line configuration where one end has two CB and CT
groups. All four current inputs to IEDs are used. Current from each CT is fed to an IED, and
currents from different CTs are processed separately by the protection algorithm. Summing
up the CTs’ secondary currents at the end with two CB and CT groups is not allowed. CBs at all
ends can be included in the protected zone depending on their positions relative to the CTs.
IEC15000461-1-en.vsd
IEC15000461 V1 EN-US
Figure 33: Three-end power line with two CB and CT groups at one end
The locally measured current samples are exchanged between all IEDs at line ends (in master-
master mode) or sent for evaluation to one master IED from all slave IEDs (in master-slave
mode).
In master-master mode, all IEDs at different ends of a protected zone execute exactly the
same program code with exactly the same information so the same response is expected from
all masters. In master-slave mode, only one IED has access to all currents in the protected
zone. It is always recommended to select the master-master mode if allowed by the number of
communication links.
4.7
Setting examples
4.7.1
Line differential protection L3CPDIF, L6CPDIF, LT3CPDIF,
LT6CPDIF
M12941-3 v8
Setting example with a power transformer in the protected zone
Figure
shows a line with a power transformer in the protected zone. Circuit impedances are
presented in Figure
. The protected zone is limited by three current transformers: CT1, CT2
and CT3. IEDs are situated in two separate substations 1 and 2.
The circuit is protected by two terminals 1 and 2. These terminals process the same data
except for minor distortion in data that takes place during communication between them.
1MRK 505 382-UEN E
Section 4
Analog and binary signal transfer for line differential protection
Communication set-up, 670/650 series
31
Application Guide
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Summary of Contents for Relion 670 series
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