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Now the calculation of the maximum differential current in the Turnpoint 2 includes before calculated
correction factors for HV and LV side CTs.
Also is needed the corrected transformation ratio effect due to the tap changer position on maximum
voltage position (usually this generates the highest differential current).
Now to get the HV volts minimum means that the calculation needs to be applied on situation when the
tap changer on secondary side is at maximum output voltage and the output is nominal. In this
example we had maximum of +12.5% increasing effect for the tap changer, and the result will be:
Next is calculated the currents flowing in this situation at HV and LV sides, when the loading of the
transformer is e.g. 1.5 times its rated power.
For LV side currents will be
And for HV side currents will be
By calculating this way these currents now present the worst possible case caused by tap changer
effect into the differential relay measured currents.
AQ-T216
Instruction manual
Version: 2.00
135
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