Question { 5925 }

For which purpose the temp. rise test of transformer is
conducted?

Answer

You see, when the current in a transformer increases, the
losses inturen increase because losses= I*I*R.

The Losses in a transformer is dissipated in the form of
heat. This is nothing but temperature rise. Hence, a
temperature rise test is conducted in order to maintain the
temperature of the windings and core within limits, and to
check the losses.

Hope that answers.

Question { 11134 }

what is meant by substation?

Answer

when a generating station produces power, the voltage is
around 11kv... This voltage is stepped up to 220kv for
transmission purpose and then at a receiving station it is
stepped down to 66kv and then transmitted to a substation
where the voltage is further droppped to around 6.6kv for
distribution purpose. So a substation is a place where
power is transmitted from receiving station and stepped
down.

hope that answers

Question { Citec, 23649 }

single phase 230v three phase voltage 415volt why we aren't
used line voltage 690v?

Answer

When you use the word three phase, it does not mean you are
connecting the voltmeter across all the three phases
(R,Y,B). The voltmeter is connected just across 2 phases,
so the line voltage across it is 440 or 415 volt. Hope that
answers