Mounting and Commissioning
3.3 Commissioning
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
315
DANGER!
Hazardous voltages during interruptions in secondary circuits of current transformers
Non-observance of the following measure will result in death, severe personal injury or substantial property
damage.
Short-circuit the current transformer secondary circuits before current connections to the device are opened.
I
4
from Own Line
To generate a displacement voltage, the e-n winding of one phase in the voltage transformer set (e.g. L1) is
bypassed (refer to Figure 3-27). If no connection to the e-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 subject to the
same conditions that exist during an earth 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 voltages can also be read out with the Web-Monitor.
The same manipulation is carried out with the current and voltage transformers at the other end.
Figure 3-27 Polarity check for I
4
, example with current transformer configured in a Holmgreen connection
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