What are the negative effects of low power factor on electrical system?

Question

What are the negative effects of low power factor on electrical system?

Answer 1

Higher heat losses for any given true power transmitted.

Answer 2

The biggest downside is if your utility charges you for the bad power factor. This would, almost certainly, justify some form of power factor correction.

Besides that, it depends if you are talking about an existing system or design of a new one.

An existing system would have higher losses but maybe not significant to justify cost of power factor correction. Of course it depends how big, how bad etc.

When designing a new system, there may be savings due to high copper prices to have smaller cables and transformers but it may not be that significant.

Even a large facility with no power factor correction would not tend to have an issue with power factor. A big cause would be over sized motors which are very inefficient anyway and should be avoided. The utility will correct the power factor anyway since they will generate using synchronous machines.

Answer 3

When the power factor is 1.0, the current and voltage are perfectly in phase with each other and the electrical system is delivering the maximum power that can be delivered by a given value of voltage and current.

When the power factor is less than 1.0, the current is negative while the voltage is positive and the current is positive while the voltage is negative during parts of each cycle. That means that some energy is circulating back and forth between the electrical system and the load rather than being converted to by the load to do useful work. A higher current is required to deliver a given flow of power.

The negative effects from the point of view of the energy supplier are reduced capacity and reduced efficiency. The capacity is reduced because the generator can only supply a certain maximum current and the power lines, transformers, etc. can only carry a maximum current. If the maximum current is reached without reaching the maximum power, the supplier can not sell as much power as the system is capable of delivering. Transmission losses are proportional to current, so the losses are higher than they would be if the same power were to be delivered by supplying a lower current. That means reduced efficiency.

From the consumer’s point of view, the power distribution components owned by the consumer have a reduced capacity. That might force the consumer to add more distribution circuits. There is also a reduced efficiency, but the total losses are much smaller, because the current flows through much shorter lengths of wire and fewer transformers etc. on the consumer side of the meter. If the supplier charges extra for low power factor, that is the biggest negative effect for the consumer.

Answer 4

If an electrical system has a low power factor, the voltage and current are out of phase, meaning that the wires will have to carry a much higher peak current than is necessary to deliver the power actually used.