Siemens SIPROTEC 7UT613 series Manual page 390

3 Mounting and Commissioning
Differential Protec-
tion
390
Note
The measurement accuracy to be achieved depends on the electrical data of the test
sources used. The accuracies specified in the technical specifications can be expect-
ed only if the reference conditions in accordance with VDE 0435/Part 303 or IEC
60255 are adhered to, and precision measurement instruments are used. The stated
tolerances refer to the preset data of the protective object. If the ( reference current
transformer rated current) rated current deviates greatly from the protective object, ap-
propriately high pickup tolerance has to be used.
Every side of the differential protection can be checked. This is consistent with the sim-
ulation of a single source error. If a side has several measuring locations, the not in a
test involved measured inputs remain at zero current. Checking the pickup value is
performed by slowly increasing the test current.
Caution!
Tests with currents that exceed more than 4 times the rated device current cause an
overload of the input circuits and may only be performed for a short time.
See Technical Data
Afterwards the device has to cool off!
Set pickup values refer to symmetrical three-phase currents for three-phase protected
objects. For single-phase transformers the currents are presumed at phase opposi-
tion. With single-phase busbar protection the summation transformers are to be con-
sidered, 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
in three-phase object and
for single-phase object with
S
N Obj
U
N Obj
For a winding with parameterised voltage according to Section 2.1.5 calculated
voltage is 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 con-
dition and current processing. This corresponds to conventional circuitry when current
is fed in via matching transformers.
Rated apparent power of the protective object
Rated voltage of the protected object or protected
transformer winding.
7UT613/63x Manual
C53000-G1176-C160-2