How does power factor affect power transmission line?

A poor power factor (less than 1) has two undesirable effects on an AC power transmission line :

1. It reduces the maximum useful power which can be transmitted along the line. The power which can be transmitted is proportional to the power factor.
2. It increases the percentage of losses along the line by a factor of 1/PF21/PF2 where PF is the power factor.

We know from the definition of Power that p=ivcos(). so i=p/vcos(). so there exist inverse relation between current and power factor so as the power factor decreases the losses in the transmission line increases and vice versa.

Loss in transmission line for low power factor

1. With low power factor we need higher rating transmission line. Plus as current transmission associated with joule loss. The more current means more joule loss. As also the reactive current travel from source to load and load end to source end too.

2. Unbalanced voltage. To maintain the voltage we need minimum amount of reactive power. But too much reactive power will make over voltage situation.

Loss in consumer side due to low power factor

1. High rating switchgear-With low power factor we will have to deal with high apparent power. Thus the switchgear like transformer, wiring, circuit breaker and other components will be of higher ratings.

2. High energy bill- The energy bill calculated on the basis of apparent power. With low power factor the apparent power is high with same active power. Thus consumer has to pay high energy bill.