FANOX SIA-F, User Manual

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3.5. Phase CT and neutral CT selection
The following table shows a summary of phase and neutral CT combinations:
Model Phase Neutral Phase range Neutral range
SIAF55 CT 5 A Residual phase connection 0,5-150 A 0,5-150 A
SIAF11 CT 1 A Residual phase connection 0,1-30 A 0,1-30 A
SIAF51 CT 5 A CT 1 A 0,5-150 A 0,1-30 A
SIAF1B CT 1 A CT 0,2 A 0,1-30 A 0,02-6 A
SIAF5B CT 5 A CT 0,2 A 0,5-150 0,02-6 A
In order to assure a correct running of the relay, it is necessary to use the proper current transformer.
Therefore, the load of measurement circuits of the relay and the load of connection cables between
CT’s and relay must be considered.
3.5.1. External current transformers advantages
It is possible to make the connection by passing the cables through the SIAF current transformers.
This solution offers more versatility because the transformation relationship can be modified.
By means of giving turns through the four current transformers of SIAF relay, CT transformation
relationship can be modified getting an easier way of relay adaptation to the final application.
i.e.
If there is a CT with Transformation relationship RT and the secondary of the CT is /1, a relay for
measurement collecting of 1 A of nominal current must be used. However, what is the necessary
action if there is a relay of 5 A of nominal current?
It is possible to give 5 turns to the secondary of the transformers of SIAF relay. Therefore, the
measurement will be multiplied by five and it would be suitable for the 5 A relay. In this case, the new
transformation relationship would be RT/5 and the relay must be adjusted accordingly with the aim of a
correct display of line current.
PRECISION BURDEN RELAYS
5P10
5P20
5P30 0,5 VA
0,5 VA
0,5 VA SIA-F/1
SIA-F/1
SIA-F/1
5P10
5P20
5P30 1 VA
1 VA
1 VA SIA-F/5
SIA-F/5
SIA-F/5