Siemens SIPROTEC 7UT613 series Manual page 48

2 Functions
48
Figure 2-2 Example for the terminology of a topology
Sides:
S1 High voltage side of the main protected object (power transformer)
S2 Low voltage 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 2
Measuring locations 3-phase, non-assigned:
M5 Measuring location, not assigned to the main protected object
Auxiliary measuring locations, 1-phase:
X3 Measuring location, assigned to the main protected object, side 1
X4 Measuring location, not assigned to the main protected object
The auxiliary measuring location X3 provides the starpoint current of the transformer.
It is assigned to side 1 of the main protected object as an assigned measuring location.
This measuring location can be used by the differential protection function for the for-
mation of the differential current. For the restricted earth fault protection operating at
the higher voltage winding, it can supply the starpoint current of side 1.
The auxiliary measuring location X4 is not assigned to the main protected object,
because it is not required by the differential protection. It is a non-assigned measuring
location which is used to detect the tank earth fault current and to feed it via the single-
phase measuring input IX4 to the single-phase overcurrent protection used for tank
leakage protection. Although tank leakage protection is in a broader sense part of the
transformer protection, X4 is not assigned to the main protection function because
7UT613/63x Manual
C53000-G1176-C160-2