Question { 3663 }

what is the maximum load sutiable from earth to phase
and what is the max voltage earth to phase suitable

Answer

Please be specific in asking your question.

max load in the sense, the max load is defined to a
particular cable that is operating at a particular voltage.

and max voltage from earth to phase means...... how can you
decide that.

a 3-ph 415V supply has a earth to phase volate of 230V,
which is the one we have in our house.

Same way a 11KV line has an earth to phase violtage of
6.3kV. and so on we go upto 800KV.

Question { 5908 }

Technical requirement of Copper earthing over GI earthing.

Answer

There arent much technical things between the two. the
current carrying capacity of the copper is more than GI.
Iron is prone to rusting after a certain time it completely
stops conducting to ground.

Question { 3934 }

why the electrical insulators suspention breakdowen

Answer

The suspension type insulator which hanges from the tower
to carry the LINE at the other end has a potential gradient
of its own. since the tower is the earth terminal, the
insulator acts as a capacitance between the line and the
earth. this also has a threshold value. so during fault
condition when high currents flow through the transmission
line the potential gradient in the insulator reaches a
saturated value and eventually breaksdown.

then the flashover between line and the tower will occur.

Question { APC, 23502 }

Why -48V dc power supply using in telecom field?

Answer

Basically for any electronic device it needs a DC supply as
a source power the different components inside it.
everybody knew that the telephone in our houe will not
contain any supply line (speaking about basic model) other
than the one that comes from the exchange. but how is the
Electronic board inside the telephone is working?

this line carries a DC voltage of 48V (42V to $8V approx).
this voltage supplies power to the components inside the
telephone as well as carries the voice signals from
exchange to our phone and vice versa.