Figure. 5.2.2. - 13. Example connections for voltage line to line measurement. Three line- to line voltages on the left and two on
the right.
In case only two line to line voltages are measured the third one is calculated based on U12 and U23
vectors. When measuring line to line voltages the line to neutral voltages can be calculated if U0 is
measured and known.
Voltage measurement channel U4 can always be used for either zero sequence voltage U0 or side 2
voltage measurement (Synchro-check). In case 2LL+U3+U4 mode is selected the third channel U3
can be used to similar purpose. Be noticed that U0 can be measured only by using one channel.
Figure. 5.2.2. - 14. Two line to line measurements with zero sequence voltage and voltage from side 2 for Synchro-check
2LL+U0+SS. Line to neutral voltages can be calculated since U0 is available.
In the next gure is presented relay behavior when nominal voltage is injected to the relay and the IED
is measuring line to neutral voltages. Part of the available information from the IED is presented as well:
AQ-T257
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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