Answer / mark from the philippines

we can use a Transfromer Turn Ratiometer(TTR) instrument to
identify the polarity of the three phase transformer. say
for wye-delta configuration at H-X format of transformer
leads, we can read the following:

H1H0/X1X2; H2H3/X2X3; and, H3H1/X3X1.
Note that Ho stands for neutral since connection is in
Y-config.

The slash (/) indicates the test lead connections, two per
sides. Good polarity indicates a positive sign value(+),
otherwise, negative(-) which means there exists a wrong
connection.

Answer / waqas

by using of phase sequencer instrument

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