When measurement scaling is made to the protected object nominal current, the object nominal
current needs also to be set into the “Nominal current In” input. The differences in the used scaling
factors can now be seen. Primary to secondary ratio is directly the ratio of the set CT ratios, CT scaling
factor to nominal is now the set CT primary to nominal current ratio, per unit scalings to primary is
changed now to nominal current and the secondary per unit factor is calculated accordingly to the
given ratio of CT primary to object nominal current.
If coarse residual current (I01) is wanted to be used for CT sum (Holmgren) input then it should be set
to phase current CT ratings 100/5A.
Figure. 5.2.1. - 6. Residual current I01 scaling to summing connection.
For the sensitive residual current (I02) measurement is set directly 10/1A rated currents.
Figure. 5.2.1. - 7. Residual current I02 scaling to ring core CT input.
If the scaling was made to CT primary or to object nominal current the measurements will look as
follows with nominal current feeding:
Figure. 5.2.1. - 8. Scalings to CT nominal.
AQ-F255
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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