Siemens SIPROTEC 7UT613 series Manual page 399

Implementation of
Symmetrical
Current Tests
7UT613/63x Manual
C53000-G1176-C160-2
formed for each possible current path (e.g. feeder 1 against feeder 2, feeder 1 against
feeder 3, etc.) Please first read the notes contained in the section „Current Testing for
Busbar Protection".
Before beginning with the first current test, check the correct polarity setting for mea-
suring location 1 on the basis of address 511 STRPNT->OBJ M1and compare it with
the actual current connections. Refer to Section 2.1.4 under margin heading „Current
Transformer Data for Three-phase Measuring Locations" for more details. This check
is also important for devices with voltage inputs as all further wrong polarities will not
be recognised because the protection functions may operate even correctly if all po-
larities are wrong. Only during power check would the errors be recognised.
For these commissioning tests the test current must be at least 2 % of the rated relay
current for each phase.
These tests cannot replace visual inspection of the correct current transformer con-
nections. Therefore, a prerequisite for this test is that the system connections have
been completely checked.
The operational measured values supplied by the 7UT613/63x allow fast commission-
ing without external instruments. The following indices are used for the display of mea-
sured values:
The equation symbol for current (I, ϕ) is following by the phase identifier L1 and by a
number that identifies the side (e.g. the transformer winding) or the measuring loca-
tion, example:
I
current in phase L1 on side S1,
L1 S1
I
current in phase L1 at the measuring location M1.
L1 M1
The following procedure applies to a three-phase protected object for measuring loca-
tion M1 against measuring 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 func-
tions in the 7UT613/63x 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 the SIPROTEC 4 System Description /1/ ).
– At the indication of imbalance there might actually be asymmetries of the primary
system. If they are part of normal operation, the corresponding monitoring func-
tion is set less sensitive (see Section 2.19.1, 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 Subsection 2.1.4 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 measured value
inputs must be checked and corrected, if required, after the measuring location
has been isolated. The phase rotation check must then be repeated.
3.3 Commissioning
399