Siemens SIPROTEC 4 7UT6 Series Manual page 366

Mounting and Commissioning
3.3 Commissioning
Set pickup values refer to symmetrical three-phase currents for three-phase protected objects. For singlephase
transformers the currents are presumed at phase opposition. With single-phase busbar protection the summa-
tion transformers are to be considered, if applicable. The rated currents of the measured current inputs are
important, if the device is connected via a summation transformer is generally 0.1 A.
When testing with the operational parameters, it should be noted that the setting value for the differential
protection refers to the rated current of the transformer, i.e. to the primary current which results from
[dreiphasenobjekt-inobj, 1, en_GB]
in 3-phase object and
[einphasenobjekt-inobj, 1, en_GB]
for 1-phase object with
S
N Obj
U
N Obj
For a winding with parameterised voltage according to Section
valid.
For transformers the actual pickup values for single or two-phase tests depend on the vector group of the
transformer; single-phase tests also depend on the starpoint condition and current processing. This corre-
sponds to conventional circuitry when current is fed in via matching transformers.
To obtain the actual pickup value, the set value has to be multiplied with the vector group factor kVG and the
following equation:
[faktor-ksg-3phasentr, 1, en_GB]
The following table shows these changes as a factor k
for three-phase transformers.
Table 3-31
Type of Fault
3-phase
2-phase
1-phase
with Ι -elimination
0
1-phase
without Ι -elimina-
0
tion
Example:
3-phase transformer
Vector Group
Rated voltage (high-voltage winding)
Current Transformer
366
Rated apparent power of the protective object
Rated voltage of the protected object or protected transformer winding.
Correction Factor k depending on vector group and fault type
VG
Reference Winding
(high voltage)
1
1
3/2 = 1,5
1
2.1.5 Setting Groups
depending on the vector group and the type of fault,
VG
even VG numeral uneven VG numeral
(0, 2, 4, 6, 8, 10) (1, 3, 5, 7, 9, 11)
1
1
3/2 = 1,5
1
S = 57 MVA
N
Yd5
U = 110 kV
Nom
300 A/1 A
calculated voltage is
1
√3/2 ≈ 0,866
√3 ≈ 1,73
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016