ABB RELION RED670 Series Product Manual page 29

Line differential protection RED670 2.2
Product version: 2.2
differential current setting
is, as shunt power transformers), without measurements of
currents in the tap, can be handled. The normal load current
is considered to be negligible, and special measures must be
taken in the event of a short circuit on the LV side of the
transformer. In this application, the tripping of the differential
protection can be time-delayed for low differential currents to
Line differential protection 3 or 6 CT sets, with in-zone
transformers LT3CPDIF , LT6CPDIF
Two two-winding power transformers or one three-winding
power transformer can be included in the line differential
protection zone. In such application, the differential protection
is based on the ampere turns balance between the
transformer windings. Both two- and three-winding
IED
Comm. Channel
IEC05000042 V2 EN-US
Figure 8. Example of application on a three-terminal line with an in-line power transformer in the protection zone
Analog signal transfer for line differential protection
The line differential protection function can be arranged as a
master-master system or a master-slave system alternatively.
In the former, current samples are exchanged between all
IEDs, and an evaluation is made in each IED. This means that
a 64 kbits/s or 2 Mbit/s communication channel is needed
between every IED included in the same line differential
protection zone. In the latter, 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 kbits/s or 2 Mbit/s
communication channel is only needed between the master
and each one of the slave IEDs. The Master-Slave condition
ABB
IdMin ) connected as line taps (that
Protected zone
Comm. Channel
Comm. Channel
IED
achieve coordination with downstream overcurrent IEDs. The
local protection of the small tap power transformer is given
the time needed to disconnect the faulty transformer.
A line charging current compensation provides increased
sensitivity of line differential protection.
transformers are correctly represented with vector group
compensations made in the algorithm. The function includes
nd th
2 and 5 harmonic restraint and zero-sequence current
M14932-3 v9
elimination. The phase-segregated differential protection with
single-pole tripping is usually not possible in such
applications.
IED
IEC05000042_2_en.vsd
for the differential function appears automatically when the
Operation for the differential function is set to Off .
setting
M13647-3 v8
For line differential protection we
recommend that all feeder ends use the
same version of RED670 and the line data
communication module LDCM. The line
differential protection in the latest version of
RED670 is compatible with older versions
of RED670. Older versions than 670 1.2.3
must be verified with ABB.
1MRK 505 379-BEN C
29