Low power factor effect in transmission and consumer electrical system

Low power factor effect has some adverse impact on both the transmission line and also in the consumer electrical system. To cope up the adverse effect better understanding of low power factor is needed.

Power factor varies from 0 to 1.

Low power factor means the reactive power is higher than the active power, as power factor is the ratio of active power to reactive power. So with a low power factor we got to deal with high amount of reactive power. Thus low power factor disadvantage is actually the disadvantage of excessive reactive power. 

In power system we need reactive power only to maintain the generate and maintain voltage. Reactive power is needed in the machine and equipment which use magnetic flux like transformer, induction motor. Also it has use transmission line to maintain the voltage.

Adverse effect of too much reactive power that is low power factor

We need active power and a little amount of reactive power. However, with low power factor the reactive power is higher than we need.

Say we need 8KW active power, with 0.80 power factor the active power is 8KW and reactive power 2kvar. So the apparent power is 10KVA. But with .60 power factor, 10KVA apparent power has only 6KW of active power.

So with low power factor the amount of apparent power is increase though the work power KW is same. This associates some significant losses both in the transmission line and in the consumer side.

1. Loss in transmission line for low power factor

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.

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

2. Loss in consumer side due to low power factor

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.

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

                              Fig: Pole mounted capacitor bank to cope up with low power factor