Siemens SIPROTEC 4 7UT6 Series Manual page 42

Functions
2.1 General
[beispiel-begriffe-fuer-topologie-270503-st, 1, en_GB]
Figure 2-2
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 Z3 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 formation 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 ΙX4 to the single-phase overcurrent protection
used for tank leakage protection. Although tank leakage protection is in a broader sense part of the trans-
former protection, X4 is not assigned to the main protection function because 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 reactor) with a three-phase measuring location and an
additional 1- phase measuring location assigned to it. While in the main protected object one side can be fed
42
Example for the terminology of a topology
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016