Phase CT scaling
Next, to scale the current to per-unit values, we have to select whether the basis of the phase CT
scaling is the protected object's nominal current or the CT primary value.
If the CT values are chosen to be the basis for the per-unit scaling, the option "CT nom. p.u." is
selected for the "Scale meas to In" setting (see the image below).
Figure. 5.2.1. - 32. Setting the phase current transformer scalings to CT nominal.
Once the setting have been sent to the device, AQtivate calculates the scaling factors and displayes
them for the user. The "CT scaling factor P/S" describes the ratio between the primary current and the
secondary current. The per-unit scaling factors ("Ipu scaling") for both primary and secondary
values are also displayed (in this case they are the set primary and secondary currents of the CT).
If the protected object's nominal current is chosen to be the basis for the per-unit scaling, the option
"Object in p.u." is selected for the "Scale meas to In" setting (see the image below).
Figure. 5.2.1. - 33. Setting the phase current transformer scalings to the protected object's nominal current.
AQ-E215
Instruction manual
Version: 2.01
35
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