51N
Three phase CT
summated
WYE/DELTA, DELTA/WYE or
WYE/WYE transformer
en05000491_ansi.vsd
ANSI05000491 V1 EN-US
Figure 272:
Residual overcurrent protection application on an isolated transformer
winding
In the calculation of the fault current fed to the protection, at different ground faults,
are highly dependent on the positive and zero sequence source impedances, as well as
the division of residual current in the network. Ground-fault current calculations are
necessary for the setting.
Setting of step 1
SEMOD55591-35 v5
One requirement is that ground faults at the busbar, where the transformer winding is
connected, shall be detected. Therefore a fault calculation as shown in Figure
made.
Section 9
1MRK 504 163-UUS A
Current protection
546
Transformer protection RET670 2.2 ANSI
Application manual
Summary of Contents for RELION RET670
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