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
34 shows a line with a power transformer in the protected zone. Circuit
impedances are presented in Figure 35. 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. Both terminals operate as masters. If at least one of them indicates
an internal fault, the protected circuit is disconnected.
IED 2
Line 50 km
CT 3
Substation 2
Substation 1
Current samples from terminals 2 and 3
Current samples from terminal 1
CT 2
Yd1
200 MVA,
220 / 70 kV,
525 / 1650 A
Y
d
220 kV, 600 A
CB 1
terminal
2 terminal
3
CB 2
CB 3
terminal
1
CT 1
IED 1
IEC05000534-2-en.vsdx
IEC05000534 V2 EN-US
Figure 34: Line differential protection with a power transformer in the
protected zone
Section 4 1MRK 505 382-UEN B
Analog and binary signal transfer for line differential protection
40 Communication set-up 670/650 series 2.2
Application Guide
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