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Functions
2.5 Power System Data 1
In this context, U
displacement voltage applied to the device. If a voltage divider is used, its division ratio also influences this
factor. The following equation results for the example in Section 2.1 Figure 2-1 „Unit connection", with the power
system data selected there and an 1:5 voltage divider ratio
Adjustment Factor Uph/Udelta
The address 225 serves to communicate the adaptation factor between the phase voltage and the displace-
ment voltage to the device. This information is relevant for measured quantity monitoring.
If the voltage transformer set has open delta windings and if these windings are connected to the device (U
input), this must be specified accordingly in address 223 (see above). Since the transformation between
voltage transformers usually is as follows:
the factor Uph/Udelta (secondary voltage, address 225 Uph / Udelta) in relation to 3/√3 = √3 = 1.73 must
be used if the Udelta voltage is connected. For other transformation ratios, i.e. the formation of the displace-
ment voltage via an interconnected transformer set, the factor must be corrected accordingly.
Protected Object: Transformer
If a transformer was specified as the protected object during differential protection configuration, the parameter
241 UN-PRI SIDE 1 appears in the Power System Data 1. It specifies the nominal primary voltage of side 1
of the protected object (transformer).
At address 242 STARPNT SIDE 1 you specify how the starpoint (Solid Earthed; Isolated) of side 1 is
treated. This setting has an influence on the measured value monitoring (summation current monitoring); in
transformer differential protection it is also important for vector group correction and the treatment of the zero
sequence current.
The setting Isolated can be chosen if the starpoint has no earthing. If the transformer starpoint is connected
to a Petersen coil or a surge voltage arrester, choose the setting Solid Earthed. The same applies to low-
ohmic or solid starpoint earthing.
The parameters 243 UN-PRI SIDE 2 and 244 STARPNT SIDE 2 determine respectively the rated primary
voltage and the starpoint of side 2 of the transformer.
Parameter 246 VECTOR GRP S2 is used to specify the vector group numeral referred to side 1 of the trans-
former. It is not necessary to specify whether the connection is delta, wye or zigzag.
At address 249 SN TRANSFORMER the rated apparent power is entered. From this the rated currents for sides
1 and 2 are calculated as follows:
These nominal currents are only considered for differential protection and can differ from the generator nominal
ratings.
56
is the primary voltage (generally phase-ground voltage) and U
VT, prim
is the secondary
E, sec
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
E
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