Protection Engineering Basics and Schemes Protection Engineering | Page 24

Now just see one wrong CT connection will result in
existing of zero sequence current, positive and negative
sequence current which means system remains no more
balance.
So it is necessary to connect CT with correct polarity and
for that we need to test CT polarity.
Now there are two methods to test any CT’s Polarity.
 Flick method
 Primary Current Injection method
Flick method is used for wound and Ring type CTs mostly,
primary current injection method is mostly used to test
polarity of outdoor CT or we say Bar type CTs.
Circuit Diagram (Flick Method)
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