Ι
L1 M1
current in phase L1 at the measuring location M1.
The following procedure applies to a three-phase protected object for measuring location M1 against meas-
uring location M2. For transformers it is assumed that measuring location 1 is assigned to side 1, and this is
the high-voltage side of the transformer. The other possible current paths are tested in an analogous way.
•
Switch on the test current or start up the generator and bring it to nominal speed and excite it to the
required test current. None of the measurement monitoring functions in the 7UT6x must respond. If
there was a fault annunciation, however, the operational annunciations or spontaneous annunciations
could be checked to investigate the reason for it (refer also to /1/ SIPROTEC 4 System Manual).
– At the indication of imbalance there might actually be asymmetries of the primary system. If they
are part of normal operation, the corresponding monitoring function is set less sensitive (see
Section 2.19.1 Measurement Supervision, under margin heading “Measured Value Supervision”).
– In general, the phase rotation is a clockwise phase rotation. If the system has an anti-clockwise
phase rotation, this must have been considered when the power system data was set (address 271
PHASE SEQ., refer to Section 2.1.4 Power System Data 1 under margin heading “Phase
Sequence”). Wrong phase rotation is indicated with the annunciation
Fail Ph. Seq. I
(No 175).
The measuring location with wrong phase rotation is also stated. The phase allocation of the meas-
ured value inputs must be checked and corrected, if required, after the measuring location has been
isolated. The phase rotation check must then be repeated.
•
Amplitude measurement with switched on test current:
Compare the indicated current magnitudes under Measurement → Secondary → Operational meas-
ured values secondary with the actually flowing values:
This applies for all measuring locations included in the test.
Note: The WEB Monitor provides comfortable read-out possibilities for all measured values with visualisa-
tion using phasor diagrams (2.22.9.1 Web-Monitor).
If deviations occur that cannot be explained by measuring tolerances, either a connection or the test
setup is wrong:
– Switch off the test source and the protected object (shut down the generator) and earth it,
– Re-check the assignment or the tested measuring location (Section 2.1.4 Power System Data 1
under margin heading “Assignment of 3-phase measuring locations”).
– Re-check the settings for the magnitude matching (Section 2.1.4 Power System Data 1 under
margin heading “Current Transformer Data for 3-phase Measuring Locations”).
– Re-check the plant connections to the device and the test arrangement and correct them.
If a substantial zero sequence current 3Ι0 occurs one or two of the currents of the corresponding
side must have a reversed polarity:
3Ι0 ≈ phase current → one or two phase currents are missing;
3Ι0 ≈ double phase current → one or two phase currents with reversed polarity
– Repeat test and re-check the current magnitudes.
Mounting and Commissioning
3.3 Commissioning
374 SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
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