7SG15 MicroTAPP Application Guide
9.1 Voltage Transformers
Either a 3 phase or single phase voltage transformers can be used for voltage measurement. A 3 phase VT is
preferable so that the level and voltage quality of all phases can be monitored. Figure 10 shows the relay
connections for a 3 phase VT.
Where a single phase VT is used it can be connected between phases or from phase to earth, in either case the
MicroTAPP set-up menu for the transformer allows the particular connection to be specified. Figure 11 shows the
connections for a single phase VT.
9.2 Current Transformers
Figures 10 and 11 also show the relay connections for a current transformer. The input allows for any CT nominal
secondary current up to 5 amps to be used. The MicroTAPP setup menu for the transformer allows the particular
ratio to be specified.
3 phase
VT
MicroTAPP
C25
C26
C27
C28
C23
C24
A
B
C
Figure 10
Single
phase VT
MicroTAPP
C25
C26
C27
C28
C23
C24
Figure 11
©2011 Siemens Protection Devices Limited Chapter 5 Page 15 of 21
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