What are the disadvantages of leading power factor?

Answer 1

When you have a Power Factor less than 1 the voltage and current waveforms in an AC circuit are out of phase. Therefore at any given instant of time the work being done or energy being expended is calculated by multiplying the current x voltage. This reduces the wattage at any instant of time. When the Power Factor is one the instantaneous multiplication of the current and voltage would yield the maximum value with the waveforms in phase. This is much easier to see with a picture, but imagine a square wave for both voltage and current. Say for half the cycle the current is 2A and Voltage 3V and for the second half of the cycle both are zero. So for 1/2 the cycle the watts generated are 6 watts and zero for the second half of the cycle. Now if the two waveforms were 180 degrees out of phase the voltage would be zero when the current was 2A and the current would be zero when the voltage was 3V for zero watts. In this case the Power Factor would be zero.

Answer 2

Any time the power factor is less than 1, whether it is leading or lagging, the efficiency is less than optimal. As power factor declines, more power is required to do the same amount of work. Leading or lagging simply refers to the load being more capacitive or inductive. The disadvantage of a lagging power factor is that the load is highly inductive. Where power factor declines, greater losses are registered in the generation/distribution/transmission areas.

Comment

Power factor has nothing to do with efficiency. As power factor reduces, the true power of the circuit is unaffected, while the apparent power increases. The operation of load devices, such as motors, are completely unaffected.

Answer 3

Leading power factor results in higher receiving end voltage, which again results in increased power loss in Transformers & Cables same as lagging power factor.