Mounting and Commissioning
3.3 Commissioning
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
273
• Close the VT mcb again: The above indication appears in the spontaneous indications as „OFF“, i.e.
„>FAIL:Feeder VT“ „OFF“.
– If one of the indications does not appear, check the connection and routing of these signals.
– If the „ON“ state and the „OFF“ state are swapped, the contact type (H-active or L-active) must be
checked and corrected.
• The protected object is switched off again.
• This check must be performed at both ends.
Current Test
The connections of the current transformers are tested with primary values. A load current of at least 5% of the
rated operational current is required. Any direction is possible.
This test cannot replace visual inspection of the correct current transformer connections. Therefore, the inspec-
tion according to Section „Checking the System Connections“ is a prerequisite.
• After closing the circuit breakers, none of the measured value monitoring functions in the 7SD80 must re-
spond. If there was a fault indication, however, the Event Log or spontaneous indications could be checked
to investigate the reason for it.
– If current summation errors occur, check the matching factors (see Section 2.1.3 at margin heading „Con-
nection of the Currents“).
– At the indication of balance monitoring 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
2.14.1 under margin heading „Symmetry Monitoring“).
The currents can be read as primary and secondary values on the display at the front, or called up in the PC
via the operator or service interface, and compared with the actual measured quantities. The absolute
values as well as the phase differences of the currents are indicated so that the correct phase sequence and
polarity of individual transformers can also be seen.
• The current amplitudes must be approximately the same. All three angles ϕ (I
Lx
–I
Ly
) must be approximately
120°.
– If the measured values are not plausible, the connections must be checked and corrected after switching
off the protected object and short-circuiting the current transformers. If, for example, the phase difference
between two currents is 60° instead of 120°, one of the currents must have a reversed polarity. The same
is the case if a substantial ground current 3I
0
occurs:
3 I0 ≈ phase current → one or two phase currents are missing;
3 I0 ≈ twice the phase current → one or two phase currents have a reversed polarity.
• The measurements are to be repeated after correcting the connections.
To Next Page
Loading...
Need help?
General
