Functions
2.1 General
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
56
This setting will not only have an impact on the displays of the operational measured values in per cent, but
it
must also be exactly the same for each end of the protected object
since it is the basis for the current com-
parison at the ends.
Topological Data for Transformers (optional)
The information under this margin heading only applies if the differential protection is configured as the main
function and if a transformer is located in the protected zone of the line protection system (device variant with
transformer option and address
143
TRANSFORMER
=
YES
is set, Section 2.1.1.3). Otherwise this section can
be skipped.
The topological data enable to relate all measured quantities to the nominal data of the power transformer.
With address
1103
FullScaleVolt.
you inform the device on the primary rated voltage (phase-to-phase) of
the transformer. The operational rated voltage is also needed for computing the current reference values of the
differential protection. Therefore, it is absolutely necessary to set the correct
rated voltage for each end of
the protected object
even if no voltages are applied to the device
.
In general, select the rated voltage of the transformer winding facing the device. However, if a winding has a
voltage control range,do not use the rated voltage of that winding but the voltage that corresponds to the mean
value of the currents at the ends of the control range of the tap changer. In this way the fault currents caused
by voltage control are minimised.
Calculation example:
Transformer YNd5
35 MVA
110 kV / 25 kV
Y-winding with tap changer
±
10 %
For the regulated winding (110 kV) this results in:
Maximum voltage
U
max
= 121 kV
Minimum voltage
U
min
= 99 kV
Voltage to be set (address
1103
)
The
OPERATION POWER
(address
1106
) is the direct primary rated apparent power for transformers and other
machines. For transformers with more than two windings, state the winding with the highest rated apparent
power. The
same operation power value must be set for each end of the protected object
since it is the
basis for the current comparison at the ends.
The power must always be entered as primary value, even if the device is generally configured in secondary
values. The device calculates the primary rated current of the protected device from the reference power.
The
VECTOR GROUP I
(address
1162
) is the vector group of the power transformer, always from the device's
perspective. The device which is used for the reference end of the transformer, normally the one at the high
voltage side, must keep the numerical index
0
(default setting). The relevant vector group index must be stated
for the other winding(s).
