Ampcontrol Pty Ltd
– ABN 28 000 915 542
IPM V2 USER MANUAL
IPM2B003 Revision 15
– MAY/18
Uncontrolled Copy - Refer to Ampcontrol Website for Latest Version
Page 22 of 83
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4.4.2 Phase Current Transformers (Terminals 9, 10, 11 & 12)
Figure 4.8: IPM Relay Electrical Connections: Phase Current Transformers
The IPM relay measures the individual phase currents of the outlet, using current transformers, to
provide input for a number of its protection functions. Current transformers should be wired to the IPM
in twisted pairs with an overall screen.
Current transformers are not ideal devices and if correct procedures are not followed during installation,
nuisance tripping can result. An ideal CT would have all the flux from the wire contained in the core and
so would accurately detect any change in current. A real CT
has “leakage fluxes”. That is, a very small
proportion of the total flux is not contained in the core, but in the space outside it and as result reduces
sensitivity of the CT. The positioning of the cables also plays a part in this effect.
The size of the error will vary from CT to CT, even those of the same type and size because of slight
differences in the core and symmetry of the windings.
To avoid nuisance tripping and false readings, consider the following during installation:
1. Keep cables as close to the centre of the toroid as possible. Do not tie them to one side of the
toroid. Remember to aim at symmetry.
2. Do not bring the cables back past the toroid within one diameter of the CT, trying to cram cables
into a small space reduces symmetry and may lead to problems, which are difficult to solve.
3. Avoid placing the CT near any device, which produces magnetic fields - whether it is a
transformer or other cables. Try to maintain several CT diameters clearance.
4. Many small cables tend to be worse than say three large ones. Try to position the CT in the
circuit with this in mind.
5. Select the smallest internal diameter CT to suit the cable size.
NOTE
The two CT-COM terminals (12 & 13) are internally connected and are
joined to earth.
A
B
C
Phase Conductors
Current TXF
1000/1 or
500/5
Current TXF
1000/1 or
500/5
IPM
Relay
CT-B
10
CT-A
9
S1
S2
P1
P2
S1
S2
P1
P2
CT-C
Current TXF
1000/1 or
500/5
11
12
S1
S2
P1
P2
Internally
Earthed
CT-COM