Answer / ram

if star connected -- two phases will work(two PTs will work)
if delta connected -- only one phase will work(refer to
single phasing problem)

Answer / ved prakash

This is in order to compensate for phase shift due to Star/Delt or Delta/Star connections of primary and secondary windings. Becuase if the phase shift is not compensated, differential protection will operate.

last week we did the REF relay test by closing single pole (R phase) of CB and apply 380V at the primary of delta transformer. we get 33A at the primary of the R phase star end. but we get 380A at both R an B in delta side. how and why?

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