Siemens SIPROTEC 4 7UT6 Series Manual page 46

Functions
2.1 General
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
A further tap of the winding can also be used as the third side. Be aware that the numbering sequence always
starts with the auto-connected winding: full winding, taps, and then accessible delta winding if required.
Auto-Transformer Banks
If three single-phase auto-transformers are arranged as a power transformer bank, the connections of the star-
point leads of the auto-windings are accessible and often provided with current transformers. During configu-
ration of the functional scope in Section
protection must be realised via the entire transformer bank, or whether you prefer a current comparison via
the winding of each phase by means of current law.
Differential protection over the entire power transformer bank:
Regarding the first case,
sides and 3 assigned three-phase measuring locations. The auto-connected winding terminals form the sides
S1 (full winding) and S2 (tap) with the assigned 3-phase measuring locations M1 and M2. As the delta
winding functions both as the tertiary winding and the compensation winding, it is the third side S3 with
measuring location M3.
The currents measured in the starpoint connections are not immediately required. However, you can assign it
to a further three-phase measuring location. The device then calculates the current sum as earth current, if
this had been set accordingly in the differential protection (see Section
The sum of the three currents measured in the starpoint leads can be connected to an auxiliary 1-phase
current input of the device (illustrated dotted) in order to use it for restricted earth fault protection and/or time
overcurrent protection. This auxiliary measuring location X3 is then assigned to both sides S1 and S2, since
the current entering the protected object at X3 must be compared with the sum of the currents at both sides.
More details with regard to the assignment are discussed later.
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2.1.3 Functional Scope
Figure 2-6 gives an example of a 3-phase presentation. In this example we have 3
you have decided whether a differential
2.2.7 Setting Notes).
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016