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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
²
opened.
from own Line
Ι
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
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.
[polaritaetspruefung-i4-holmgreen-101010, 1, en_US]
Figure 3-31
If the current flows towards the protected object according to the circuit in
are virtually zero. A ground current 3Ι
V
is missing and a zero sequence voltage 3V
AGnd
In the event of a polarity fault, 3Ι
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.
SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
Figure
3-31). If no connection on the g–n windings of the voltage transformer is available,
Polarity check for Ι
, Example for a current transformer set in Holmgreen configuration
4
of the approximately same level as Ι
0
is in opposite phase with Ι
0
appears.
0
or the zero voltage 3V
A
Mounting and Commissioning
3.3 Commissioning
Figure
3-31, the currents Ι
B
occurs. Accordingly, the voltage
A
supplements the other
0
and Ι
C
243
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