Siemens SIPROTEC 7UT613 series Manual page 413

7UT613/63x Manual
C53000-G1176-C160-2
The voltages can be read on the display at the front, or called up in the PC via the op-
erator or service interface, and compared with the actual measured quantities as
primary or secondary values. Besides the magnitudes of the phase-to-phase and the
phase-to-earth voltages, the phase angles can be read out, thus enabling to verify the
correct phase sequence and polarity of individual voltage transformers. The voltages
can also be read out with the „Web Monitor" (see figure 3-40).
• The voltage magnitudes should be almost equal. All angles must be approximately
120° to each other in a 3-phase system.
– If the measured quantities are not plausible, the connections must be checked
and revised after switching off the measuring location. If the phase difference
angle between two voltages is 60° instead of 120°, one voltage must be polarity-
reversed. The same applies if there are phase-to-phase voltages which almost
equal the phase-to-earth voltages instead of having a value that is √3 greater.
The measurements are to be repeated after setting the connections right.
– In general, the phase rotation is a clockwise phase rotation. If the system has an
counter-clockwise phase rotation, this must have been considered when the
power system data was set (address 271 PHASE SEQ., refer to Subsection 2.1.4
under margin heading „Phase Sequence"). Wrong phase rotation is indicated
with the annunciation „Fail Ph. Seq. U" (No 176). The measured value al-
location must be checked and corrected, if required, after the measuring location
has been isolated. The phase rotation check must then be repeated.
Figure 3-40 Phasor Diagram of the Primary Measured Values — Example
3.3 Commissioning
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