Siemens SIPROTEC 7UT613 series Manual page 49

7UT613/63x Manual
C53000-G1176-C160-2
single-phase overcurrent protection is an autonomous protection function without any
relation to a specific side.
Figure 2-3 shows an example of a topology which in addition to the main protected
object (the three-winding transformer) has another protected object (the neutral reac-
tor) with a three-phase measuring location and an additional 1-phase measuring lo-
cation assigned to it. While in the main protected object one side can be fed from
various measuring locations (this is the case for the high-voltage side S1 of the trans-
former, which is fed by M1 and M2), no sides are defined for the additional protected
object. Nevertheless, other protection functions (not the differential protection) can act
on it, such as the overcurrent protection (3-phase on M5), the earth overcurrent pro-
tection (1-phase on X4), or the restricted earth fault protection, which compares the
triple zero sequence current from M5 with the earth fault current of X4.
Figure 2-3 Topology of a three-winding transformer as main protected object and a neutral
reactor arranged outside of the protected zone as a further protected object;
right hand three-phase illustration of the neutral reactor
Sides:
S1 High voltage side of the main protected object (power transformer)
S2 Low voltage side of the main protected object (power transformer)
S3 Tertiary winding side of the main protected object (power transformer)
Measuring locations 3-phase, assigned:
M1 Measuring location, assigned to the main protected object, side 1
M2 Measuring location, assigned to the main protected object, side 1
M3 Measuring location, assigned to the main protected object, side 2
M4 Measuring location, assigned to the main protected object, side 3
Measuring locations 3-phase, non-assigned:
M5 Measuring location, not assigned to the main protected object, associated with the
neutral reactor
Auxiliary measuring locations, 1-phase:
X4 Measuring location, not assigned to the main protected object, associated with the
neutral reactor
2.1 General
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