Siemens SIPROTEC 7SD80 Manual page 276

Mounting and Commissioning
3.3 Commissioning
I from Own Line
4
To generate a delta voltage, the broken delta winding of one phase in the voltage transformer set (e.g. A) is
bypassed (refer to Figure 3-31). If no connection on the g–n windings of the voltage transformer is available,
the corresponding phase is open circuited on the secondary side. Via the current path only the current from the
current transformer in the phase from which the voltage in the voltage path is missing, is connected; the other
CTs are short-circuited. If the line carries resistive-inductive load, the protection is in principle subjected to the
same conditions that exist during a ground fault in the direction of the line.
The voltages can be read 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 as primary or secondary values. The absolute values as
well as the phase differences of the voltages are indicated so that the correct phase sequence and polarity of
individual transformers can also be seen.
The same manipulation is carried out with the current and voltage transformers at the other end.
Figure 3-31 Polarity check for I
If the current flows towards the protected object according to the circuit in Figure 3-31, the currents I
are virtually zero. A ground current 3I
V is missing and a zero sequence voltage 3V
AGnd
In the event of a polarity fault, 3I
two voltages to a voltage star. Open the circuit breakers, short-circuit current transformers and set current and
voltage transformer connections right and repeat the test.
Note
If parameters were changed for this test, they must be returned to their original state after completion of the
test !
276
, Example for a current transformer set in Holmgreen configuration
4
of the approximately same level as I
0
appears.
0
is in opposite phase with I
0 A
occurs. Accordingly, the voltage
A
or the zero voltage 3V supplements the other
0
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
and I
B C