i have 28/32 MVA power transformer with 11/6.6 KC voltage
rating and 12%impedance.it have star connection at both
side.but it have another thied winding tertiary
winding.what is used of this winding.

pl tell me

Answer Posted / ajay patel

How your tertiary Winding is connected? what is the rating?
If all three phase terminals are bruoght out then it can be
used as additional seondary winding. But If this tertiary
is connected in Open Delta & 2 termianls of open delta
brought our for Earthing. That means this is installed for
Harmonic purpose. If you have rectifier, Big VFDs or such
load which can generate Theird Harmonic in big amount then
these third harmonic can be reflected in entire Grid, if
your transformer is Star - Star. Which is may damage other
equipments / consumers also who are connected with same
supply. Hence it is necessory to control 3rd harmonics in
grid. For this you can provide Delta Primary for
Transformer. But you dont have delta in primay tehn you
have to provide Tertiary winding with open Delta. This Open
delta is closed out side of Transformer & Complete Delta is
formed. This Delta winding should be earthed to minimise
harmonic disturbance in the system. Please check, do you
have earthed tertiary? Is it in Delta?

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