Siemens SIPROTEC 7UT613 series Manual page 54

2 Functions
54
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 mea-
suring 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.
Figure 2-6 Topology of a transformer bank consisting of 3 single-phase auto-transformers
with compensation winding dimensioned as accessible tertiary winding
Sides:
S1 High voltage side of the auto-connected winding of the main protected object
S2 Low voltage side (tap) of the auto-connected winding of the main protected object
S3 Tertiary winding side (accessible compensation winding) of the main protected object
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 2
M3 Measuring location, assigned to the main protected object, side 3
Auxiliary measuring locations, 1-phase, assigned to the main object (current sum of the
CT set):
X3 Measuring location, assigned to the main protected object, side 1 and 2
7UT613/63x Manual
C53000-G1176-C160-2