EXAMPLE 1:
[dw_bsp1uwdl_anpassfaktor, 2, en_US]
Figure 5-2 3-Phase Voltage Transformer: Connection = 3 Phase-to-Ground Voltage + VN
If the connection type of the voltage transformer is 3 ph-to-gnd volt. + VN (parameter: VT connec-
tion ) and the voltage input V4 is connected to the broken-delta winding of the voltage transformer (da/dn),
the Matching ratio Vph / VN is as follows:
When changing the neutral point according to Figure 5-2, this results in the following values:
•
The calculated secondary zero-sequence voltage V
0 sec
is equal to the secondary phase-to-ground voltage.
Expressed as secondary transformer rated voltage, then V
rated sec
/√3.
•
The measured residual voltage on the broken-delta winding is the sum of the voltage drops on the 3
sides. Expressed with the side ratio, the result is V
N, sec
= 3 V
rated,sec
/3.
Calculate the Matching ratio Vph / VN parameter as follows:
[fo_bsp1, 2, en_US]
Set Matching ratio Vph / VN = 1.73.
In example 1 V
rated sec
, the phase-to-ground voltage and the secondary voltage on the broken-delta winding
were identical. If these voltages are different, use the actual numerical values in the calculation.
EXAMPLE 2:
Phase-to-ground voltage V
rated sec
= 100 V
Broken-delta winding (for
example, grounding trans-
former in generator protection)
V
rated sec
= 500 V
The voltage input of the device is designed for a continuous operation,
using 230 V max. Therefore, the voltage on the broken-delta winding (500
V) is reduced to a 5:2 ratio, using an Ohmic divider. In order to calculate the
matching factor, the secondary voltage of 200 V will be applied.
Calculate the Matching ratio Vph / VN parameter as follows:
Function-Group Types
5.1 Power-System Data
184 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017
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