ABB Relion 670 Series Applications Manual page 218

Section 7
Current protection
Capacitor Unit
(Can)
IEC09000753 V1 EN-US
Figure 115: Replacement of a faulty capacitor unit within SCB
There are four types of the capacitor unit fusing designs which are used for construction of SCBs:
Externally fused
Internally fused
Fuseless
Unfused
Which type of fusing is used may depend on can manufacturer or utility preference and previous
experience.
Because the SCBs are built from the individual capacitor units the overall connections may vary. Typically
used SCB configurations are:
212
where an individual fuse, externally mounted, protects each capacitor unit.
where each capacitor element is fused inside the capacitor unit
where SCB is built from series connections of the individual capacitor units (that is, strings) and
without any fuses
where, in contrary to the fuseless configuration, a series or parallel connection of the capacitor units
is used to form SCB, still without any fuses
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1MRK 505 370-UUS Rev. K
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IEC09000753_1_en.vsd
Busbar protection REB670
Application manual