ABB RED650 Applications Manual

Section 1
UnrestrainedLimit
Section 2
Section 3
Restrain
Operate
unconditionally
5
4
3
2
1
0
0 1 2 3 4 5
IdMin
EndSection1
EndSection2
Restrain current
[ in pu of IBase]
Operate current
[ in pu of IBase]
SlopeSection2
SlopeSection3
en05000300.vsd
Operate
conditionally
IdMinHigh
A
C
B
IEC05000300 V1 EN-US
Figure 33: Overestimated charging current
If a high resistive fault is considered, the voltage in the fault location will not be
much reduced. Consequently, the value of the pre-fault “false” differential current
will be a good estimation of the actual charging current.
Subtracting the pre-fault charging current from the differential current under fault
conditions will make it possible to set Idmin mainly without considering the
charging current in order to achieve maximum sensitivity. The stability at external
faults will not be affected.
6.1.2.4 Time synchronization
M12022-66 v3
Time synchronization of sampled current values is a crucial matter in numerical
line differential protections. The synchronization is made with the so called echo
method, which can be complemented with IRIG-B time synchronization. In
applications with symmetrical communication delay, that is, send and receive times
are equal, the echo method is sufficient. When used in networks with asymmetrical
transmission times, the optional IRIG–B time synchronization is required.
6.1.2.5 Communication channels for line differential protection
M12022-69 v7
The line differential protection function uses 64 kbit/s communication channels to
exchange telegrams between the line differential protection IEDs. These telegrams
Section 6 1MRK 505 393-UEN B
Differential protection
82 Line differential protection RED650 2.2 IEC
Application manual

ABB RED650 Specifications

General

Brand	ABB
Model	RED650
Category	Protection Device
Language	English