Answer / sriram

the transmission of electrical energy have some losses. if
we step down directly from 33kv to 415v. the resulting
voltage may only an under voltage. in order to avoid that
we have some restrictions.

Answer / anonymous

11kv is basically for primary distribution say to a large
factory. so at a substation, stepping down to 11kv for such
use and further stepping down to 415V for residential areas.

Answer / kiran

It is not advisable to step down directly for following
reasons.
a) If insulation between 33kV and 415V winding fails, then
before triping, for a fraction of second 33kV high voltage
will get connected to 415V system, on which vast users &
equipments are connected.
b) Fault level on 33 kV is more, hence if fault occures on
415V bus side, heavy kA fault current will flow as compared
to 11kV/415V transformer.


But nowadays, 33kV/415V transformers are widely used to
avoid double transformers

Answer / nikul polara

when we use this type of system we provide in cable
insulation level is very high and we dont use 11kv in
industrial area.

Answer / lee onn

It is cause the wagamama theory. 1+1 =3

Answer / sunil walia

In the past the Electricity take over points were at 11 KV
and feeders used to be 11 KV feeders. Stepping down to 415 V
was done for individual pockets. Subsequently State
electricity boards mandated that electric supply will be
given at 33 KV or above depending on load. Hence, takeover
was converted to 33KV, However the old 11KV feeders were not
replaced. So stepping down was done in two stages ie
33KV/11KV and 11KV/415V. Now in some all new townships
33KV/415V is being with feeders at 33KV. However, this is
limited because of the ambient quality and cost of 33KV
cables, switch gear etc. Considering the industrial quality
and output 33KV/11KV and 11KV/415V circuits shall be used.

Answer / raviteja nowduru

a)in a 33/11 kv transformer has more current on secondary.if
it is 33/.415 kv much more current in secondary .so
conductors on secondary should be designed to 415v ,and for
a large current.
But if it is 33/11kv transformer they will be distributed
to various 11/.415 kv transformers.so current capacity of
conductors are decreased.

Answer / hosam

33kv to 11kv 20MvA 2TX 415v 16MW & 33kv to .433v pole mounted or Ground mounted tx 1000kva/.433 voltage increased between 33kv to 11kv that why use tx 33kv11kv we can use also 66kv to 33kv and 6.6kv with 33kv to 6.6kv cable connection 3Cx300mm.sq for 33kv and 11kv use to connection 3Cx240mm.sq.

Answer / gulshan goyal(knit->iitk)

distribution transformer energised 24 hours hence there
are continious core losses which in turn depends on
voltage.Hence to reduce core losses transformer is
energised 24 hours at lower(11kv) voltage.

Answer / rakesh singh

The fault level of 33 KV/.415KV transformer is less as
compaired to the 11KV/.415KV.So during the faulty
conditions the fault current will be high in the first case
and for the lighting circuit we will have to put lighting
transformers to reduce the fault level up to the fault with
stand capacity of lighting switch gears which are available
up to 10 KA only.
But for the power circuit i.e for MCC and PMCC for whitch
switch gear of 35 KA and 50 KA are available we can use 33
KV/.415KV transformer loking to our total load and
availabilty of supply at 33 KV volatage level.

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