1 2 3 4 A - SIPROTEC

Mounting and Commissioning
3.3 Commissioning
452
Figure 3-49 Triggering oscillographic recording with DIGSI — example
Oscillographic recording is immediately started. During the recording, an annunciation is output in the left area
of the status line. Bar segments additionally indicate the progress of the procedure.
The SIGRA or the Comtrade Viewer program is required to view and analyse the oscillographic data.
Such test records are especially informative on power transformers when they are triggered by the switch-on
command of the transformer. Since the inrush current may have the same effect as a single-ended infeed, but
which may not initiate tripping, the effectiveness of the inrush restraint is checked by energising the power
transformer several times.
The trip circuit should be interrupted or the differential protection should be switched to DIFF. PROT. = Block
relay (address 1201) during these tests in order to avoid tripping.
Conclusions as to the effectiveness of the inrush restraint can be drawn from the recording of the differential
currents and the harmonic contents. If necessary the inrush current restraint effect can be increased (= smaller
value of the 2nd harmonic in address 1271 2. HARMONIC) when trip occurs or when the recorded data show
that the second harmonic content does not safely exceed the restraining threshold (address 1271). A further
method to increase inrush restraint is to set the crossblock function effective or to increase the duration of the
crossblock function (address 1272 CROSSB. 2. HARM) (For further details refer to the setting information for
differential protection under „Harmonic Restraint“).
Note
Do not forget to switch on the differential protection (address 1201) after completion of the test.
SIPROTEC, 7UT6x, Manual
C53000-G1176-C230-2, Release date 06.2012