Figure 3.6. Ct Connection And Release Contact; Figure 3.7. Multi Ratio Ct; Figure 3.8. Summation Ct - ABB APC Series Installation, Operation And Maintenance Instructions

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
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
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.
16

Figure 3.6. CT connection and release contact

l
. The C.T. ratio should be selected as near as possible to suit the supply loading.

Figure 3.7. Multi ratio CT

Figure 3.8. Summation CT

Gray jumper to short-circuit the
CT secondary winding
Power release contact
remote control
k l
and respectively as before.
APC - Chapter 3. Installation
for