Answer / seraj

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
system responds.
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.

Answer / manjeet

KWH CONSUMPTION AND LOSSES REDUCES.

Answer / balaji

it means that the supply is connected to the resistive
load.then reactive power becomes zero thus increase in the
system efficiency

Answer / rakesh ampuri

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.

Answer / g.v.suresh kumar

SENDING END VILTAGE=RECEVINRG END VOLTAGE+POWER LOSSES
AT UNITY P.F THERE IS NO LOOSES SO
SENDING END POWER=RECEIVING END POWER

Answer / rabia

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?"

Answer / rathnam

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
generating stations)

Answer / rajendra

if sending end power at upf means only active power and reactive power is zero but at reciveing end side most are inductive load we need reactive power. so we never transmitted power at unity pf

Answer / h r jadhav

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.

Answer / karthik

i dnt think transmitting at unity pf. we can produce
voltage in that we normelly used to gen at 0.9 leading pf.
we couldnt go beyond this limit bcz of over rotor heating.
if we use this power for more number of motors and
lightings which is having low power factor the resultant
current drawn from the gen station ll be lagging only..
power factor purely depends on load only. at gen station we
can go upto alternator allowed range of leading pf..


if we consider this question as in the distribution station
if we try to deliver power at unity pf we may fail to judge
the load pf at each instant.. it may vary time to time..

even we further concentrate and done it we can minimise the
losses in line and billing of industry may reduce bcz of
UPF @ they r charged by KVAh tariffs...

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