when ac power supply is done with unity pf then line loss
can be eleminated volage profile of recieving end become
flate there would not be need compensesion . proper
utilization ele. power can be improved ele. m/c performence
would b increase efficiency would also increase.
IF WE TAKE UNITY POWER FACTOR IN TRANSMISSION
WE KNOW THAT POWER FACTOR ARE INVERSELY PROPORTIONAL TO CURRENT
MEANS SO MANY LOOSES OCCUR AND ALSO SIZE OF CONDUCTOR
INCREASE, CAPITOL CAST INCREASE
POWER TRANSMISSION MAY BE COSTLY
As we know transmission lines are having high X/R ratio ,
nearly 13 for 400kv line and below that for low voltage
levels and more for high voltage levels, so even if we
transmit power at UPF at the sending end, we receive power
at lagging power factor (at high loads) and leading power
factor (at low or no load condition).
But it is possible to send power at unity power factor (at
If it is made possible to deliver AC power with unity power
factor, it would be most economical for the company as
there would be minimum line losses. Total current would be
active only contributing for watts.
The system stability will however be poor, as there will be
no cussion for variation in load. Be disconnection of a
large load, the system will go over voltage and over
frequency before the mechanical system of the connected
generators respond to decrease the load of the turbines.
similarly if a large load is at once connected to the
system, there will be instantaneous mismatch between inflow
and outflow of power. This will cause the system to go
under voltage and under frequency before the mechanical
If power factor is less than unity, in both of the above
cases, the surge will be absorbed by the inductive cussion
(just like a flywheel in mechanical system) and the sytem
would be more stable.
So we can say power factor adjustment is a compromise
between economy and the stability of the system.
when we transmitte bulk power,from sending end to receiving
end ,the system naturaly demand potetial difference. there
shall be some what reactive power in grid otherwise grid
will be colapsed.so it seems imaginary.
I consider the answer posted by Seraj to be correct. Most
of the other answers are also partially correct like the
ones posted by Manjeet and Rakesh Rampuri; one can not mark
them incorrect. But these answers do not address the
question "What happens". I suppose the question has been
asked with the thinking in mind that if unity power factor
is the ideal condition having minimum line losses; then why
is it not recommended to keep power factor exactly or very
close to unity?
We should not ask the opinion for the answer simply correct
or incorrect. We should rather ask "Is this a correct and
complete reply to the question?"
We are using 3core 11KV HT cable for same phase for
generator outgoing, the cable leakage current is high and
cable heated overly what is the remidy, if we use the 3core
cable for 3phases the problem is solved are not?
On monitor it is written that current rating is 2.2 Amps.
Is it a monitor current drawing capacity or CPU & monitor.
If it is only monitor rating, what will be the rating of
only CPU and what will be the power consumption rating of
PC, Monitor & Scanner?
In net, I learnt that computer consumes only 200-300W while
running. With the current rating of 2.2 Amps, how it could
be 200-300Watts. Please explain?