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What is Power Factor?
Power factor is an expression of energy efficiency. It is usually expressed as a percentage and the lower the percentage, the less efficient the power usage is within an electrical system.
If a circuit were 100% efficient, demand would be equal to the power available. A power factor closer to 1 (100% - unity) is desirable with 0.99 (99%) achievable in well provisioned systems.
Why do we need to know this?
When demand is greater than the power available, a strain is placed on the utility system. Many utilities add a demand charge to the bills of large customers to offset differences between supply and demand (where supply is lower than demand).
Correcting power factor or reducing the Reactive Power means that we only need to procure “Working electricity” and thus reduce the waste and save costs.
We can better demonstrate how power factor impacts your energy distribution network using the “beer analogy”.
The Beer Analogy
Beer is active power (kW):
The useful power, or the liquid beer, is the energy that is doing work. This is the part you want.
Foam is reactive power (kVAR):
The foam is wasted power or lost power. It’s the energy being produced that isn’t doing any work, such as the production of heat or vibration.
The mug is apparent power (kVA):
The mug is the demand power, or the power being delivered by the utility.
The impact of untreated Harmonics
Under identical load conditions, cables and switchgear without power factor correction equipment, experiences increased current flow. This can lead to the risk of cable overload, subsequent overheating and ultimately electrical failure.
Poor Voltage Regulation
Voltage in the system is badly affected and voltage regulation is poor - Load end voltage variations between low load and full load is higher.
Underutilisation of Grid Capacity
Generation capacity is underutilised since generation assets are rated in total kVA capacity (kVA).
Increased Distribution Network Noise
Low power factor can exacerbate noise on thyristor circuits (Variable Speed Systems etc.) and power electronic systems - This leads to magnified harmonics contents which affects supply quality.
Increased Copper Losses
Copper losses in transformers and distribution networks increase under the same load conditions - System efficiency suffers.
Reduced Asset Life
Switching can cause high voltage surges due to reactive nature of load.
The benefits of Power Factor
With the implementation and maintenance of load appropriate PFC, one can expect:
Reduced Energy Procurement
When power factor correction (PFC) is implemented, it optimises the efficiency of electrical systems, reducing the amount of apparent power required to meet the same electrical demand.
Extended Plant
Life
Power factor correction reduces the stress on electrical equipment such as transformers, cables, and switchgear by minimizing reactive power flow. This results in less wear and tear on these components, ultimately extending their operational lifespan.
Overall Better Performing Equipment
With optimal power factor, electrical equipment operates more efficiently and reliably. This translates to improved performance across the board, including better voltage regulation, reduced overheating, and smoother operation of machinery and electronic systems.
