8/13/2019 Three Winding Transformers and Harmonics
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THREE WINDING TRANSFORMERS AND HARMONICS
Three winding transformers wyewyede!ta with the de!ta not
"onne"ted to any !oad# the ne$tra!s of
the %wye% are gro$nded and these transformers are $sed to
s$&&!y an ind$stria!'mining fa"i!ity( I)*eheard that this
is to tra& +ero se,$en"e "$rrents in the de!ta whi"h "ome from
the se"ondary -wye.
and a*oid !etting them f!ow $&stream thro$gh the &rimary
-wye.(
My ,$estions are the fo!!owing/
0( If a wyewyede!ta transformer is $sed for %tra&&ing%
third -or other tri&!e1. harmoni" "$rrents
wo$!dn)t it 2e "hea&er to insta!! a reg$!ar twowinding
transformer with harmoni" fi!ters t$ned to
the s&e"ifi" harmoni" "$rrent3 Moreo*er4 wo$!dn)t it 2e
"hea&er to insta!! a de!tawye transformer-de!ta on the
&rimary or high*o!tage side.
5( What)s the &$r&ose of ha*ing wye gro$nded
"onfig$ration on the &rimary and the se"ondary3
In the mean time I wi!! sear"h for my o!d 2oo6s and try to
ana!y+e the &ositi*e4 negati*e and +erose,$en"e networ6s with
different transformer "onfig$rations to see if I "an get and
answer(
. Harmoni" fi!ters need to 2e t$ned to "ertain order-s. of the
harmoni"s( To maitain then is e1tra
"ost( De!tawye t1 is genera!!y at a higher "ost as the de!ta
windings need f$!! 7I8 ins$!ation designthan wye
5. Need wyewye t1 no &hase ang!e shifting( Gro$nded wye on
2oth side to ho!d &hase to
ne$tra! *o!tage in &!a"e on &rimary# &ro*ide
&ower to sing!e &hase !oad on se"ondary(
Than6s for yo$r answer 9WTRAN4
If we "onsider that the three winding transformer is
s$&&!ied 2y a 5:; or 00< 6= networ6 and these"ondary is
:>(< 6= I ha*e the fo!!owing ,$estions 2ased on 9WTRAN
res&onse/
0( In genera! a three winding transformer is "hea&er than
2$ying a reg$!ar two winding transformerwith a se&arate
harmoni" fi!ter &!$s the "ost of the swit"hgear C7 for the
fi!ter3
5( 9ro*ided that the se"ondary is :>(< 6=4 no sing!e
&hase !oads are s$&&!ied( I sti!! don)t $nderstand
the need for a &rimary and se"ondary wye gro$nded
"onne"tion( In my !mited e1&erien"e4 for
ind$stria! &$r&oses I)*e seen main transformers with a
det!awye "onfig$ration(
A!so4 I wo$!d !i6e to "onfirm my initia! statement that a three
winding transformer where the&rimary and se"ondary ha*e wye
"onfig$ration and the tertiary is de!ta is $sed to %tra&%
third
harmoni" "$rrents in the de!ta(
Is there generation on the !ow side of the transformer3
In many "ases it "an 2e !ess e1&ensi*e to 2$i!d a wyewye
with a three!egged "ore and a de!ta
tertiary than it wo$!d 2e to 2$i!d a two winding wyewye on a
fi*e!egged "ore(
I dont thin6 the sta2i!ising tertiary winding in a star'star
transformer is to %tra&% harmoni"
"$rrents(Its &$r&ose was to -0. to sta2i!ise the ne$tra!
&oint of the f$ndamenta! fre,$en"y *o!tages-5. to &rote"t
the tarnsformer and system from e1"essi*e third harmoni" *o!tages
-:. to &re*ent
te!e&hone interferen"e d$e to third harmoni" "$rrents and
*o!tages in the !ines and earth(
