ABB APC Series, Installation, Operation And Maintenance Instructions

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APC - Chapter 3. Installation 16
en
Gray jumper to short-circuit the
CT secondary winding
Power release contact for
remote control
Figure 3.6. CT connection and release contact
When a multi ratio split core C.T. is used the appropriate ratio is selected by connecting either S2 or S3 or
S4 to terminal marked
l
. The C.T. ratio should be selected as near as possible to suit the supply loading.
Figure 3.7. Multi ratio CT
When a summation current transformer is used the terminal markings will usually be P1, P2, P3, P4 and
S1, S2. The secondary connections S1 and S2 should be made to
k
and
l
respectively as before.
Figure 3.8. Summation CT
The first C.T. should be connected with S1 and S2 to P1 and P2 on the summation C.T. while the second
C.T. should be connected with S1 and S2 to P3 and P4 on the summation C.T. It is important that all CTs
monitor current in the same direction.
When a summation C.T. is used or the CT monitors only part load (i.e. two cables per phase with the C.T.
on one cable only) the total system current that gives 5A in the relay current coil is used to calculate relay
setting.