ABB Relion 670 Series Applications Manual page 99

1MRK 505 370-UUS Rev. K
6.1.2 Basic applications
6.1.2.1 General
Basic types of applications for REB670 IED are shown and described in this chapter. For these
applications usually three phase version of the IED, with two differential zones and four (or even eight) 3-
phase CT inputs, is used.
6.1.2.2 Meshed corner application and T-connection application
The REB670 general differential function is suitable for application on mesh-corner arrangements. Mesh
corners might have four or even up to six CT inputs and are basically simple single busbar
arrangements. A similar application will occur when a T-protection is required for breaker-and-a-half or
ring busbar arrangements.
ANSI11000237 V1 EN-US
Figure 40:
6.1.3 Busbar protection applications
A busbar protection scheme design depends very much on the substation arrangement. Complexity of
the scheme can drastically vary from station to station. Typical applications problems, for the most
common busbar protection schemes, are described in this chapter.
6.1.3.1 General
A busbar protection is a device which protects busbars against short-circuits and ground-faults. In the
early development of electricity systems, no separate protection device was used for busbar protection.
Remote end line protections were used as main protection for busbar faults. With the increased short-
circuit power in the network separate differential IEDs for busbar protection have to be installed in order
to limit the damage caused by the primary fault currents. At the same time, it is also a must to secure the
network stability, as a delayed tripping for busbar faults can also lead to network instability, pole slip of
near-by generators and even total system collapse.
For bus zone protection applications, it is extremely important to have good security since an unwanted
operation might have severe consequences. The unwanted operation of the bus differential IED will have
Busbar protection REB670
Application manual
252
ANSI11000237-1-en.vsd
Example of REB670 application on T-connection
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Section 6
Differential protection
SEMOD127448-1 v1
M12097-3 v3
M12098-3 v4
SEMOD127456-1 v2
M12102-3 v4
M12103-3 v3
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