Figure 558: Functional module diagram
9.5.4.1
Voltage and current measurements
The measured voltage must be a phase-to-phase voltage from the regulated
side. Typically, it is the phase-to-phase voltage U_AB from the secondary side of
the power transformer. If the phase voltages are measured, the voltage U_AB is
calculated internally in the IED.
Currents from the secondary side of the power transformer (I_A – I_C) have several
uses.
• The highest phase current value is used for overcurrent blocking.
• The currents from the secondary side of the power transformer are used for line
drop compensation (average of the connected inputs).
1MRS757644 H
Control functions
620 series
Technical Manual
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