Siemens SIPROTEC 7UT613 series Manual page 125

Phase Dedicated
Connection
Connection via
Summation CT
7UT613/63x Manual
C53000-G1176-C160-2
For each of the phases, a 7UT613/63x is used in case of single-phase connection. The
fault current sensitivity is equal for all types of faults. 7UT613 and 7UT633 are suitable
for up to 9, 7UT635 for up to 12 feeders.
The differential protection feature of the 7UT613/63x refers all currents to the rated
current of the protective object. Therefore, a common rated current must be defined
for the entire busbar even if the feeder CTs have different rated currents. This common
rated current has been set in address 371 I PRIMARY OP.. It is the maximum of the
rated currents of all feeders set in the device in the data of the protected object. Mea-
sured value matching in the device is thus limited to current quantity factors. No exter-
nal matching devices are necessary even if the feeders and/or the current transformer
sets at the ends of the protected zone have different primary currents.
Figure 2-42 Single-phase busbar protection, illustrated L1
One single device 7UT613/63xis sufficient for a busbar with up to 7 feeders if the
device is connected via summation current transformers. The phase currents of each
feeder are converted into single-phase current by means of the summation CTs.
Current summation is asymmetrical; a different sensitivity is thus valid for different
fault types. 7UT613 and 7UT633 are suitable for 9, 7UT635 for 12 feeders.
A common nominal current must be defined for the entire busbar. Matching of the cur-
rents can be performed in the summation transformer connections if the feeder CTs
have different nominal currents. The output of the summation transformers is normally
designed for IM = 100 mA at symmetrical rated busbar current. The nominal current
at the device input I
N Obj
= 100 mA is applicable.
2.2 Differential Protection
125