Disadvantages of Low Power Factor: From All Angles

If you’re running an industrial or commercial facility, you’ve likely heard of “power factor” and its importance to your operations. Whether you’re a seasoned engineer or a new business owner, understanding the disadvantages of low power factor can help you improve your facility’s efficiency, reduce energy costs, and prevent equipment damage. So let’s get started!

The power factor is the percentage of electricity that is being used to do useful work. It is defined as the ratio of “active or actual power” used in the circuit measured in watts or kilowatts, to the “apparent power” expressed in volt-amperes or kilo volt-amperes.

The power factor is usually expressed as Cos Phi. (Ø) and can get values in the range from 0 to 1. The value of the power factor can never be more than 1.

Power factor can be calculated by using the below formula:

Power factor = cos ϕ = P(kW) / S(kVA)

P= Active power (kW) does the real work of running the motor.

Q= Reactive power (kvar) is the power used for magnetization, etc.

S= Apparent power (kVA) is the geometrical or vector sum of kW and kvar

Disadvantages of Low Power Factor

Disadvantages of low power factor are:

1. Large conductor cross-sections

At the low power factor, for transmitting the same quantity of useful power, a larger cross-section of the conductor is required. Because of the low power factor, more current is required to fulfill the useful power demand of consumers.

This is one of the reasons why power companies strive to maintain a high power factor in their power systems. By improving the power factor, the same amount of useful power can be delivered with less current, which reduces energy losses and improves the efficiency of the system.

2. Big equipment size

The electrical machinery (e.g., alternators, transformers, switchgear) is always rated in kVA. kVA rating of the electrical equipment increases due to the low power factor as the power factor is inversely proportional to the KVA rating of the equipment. This increases the size and cost of the equipment such as transformers, alternators, and switchgear.

For example, if a motor has a power rating of 100 kW and a power factor of 0.8, its apparent power would be 125 kVA (i.e., 100 kW/0.8 PF). However, if the power factor is reduced to 0.6, the apparent power would increase to 166.67 kVA (i.e., 100 kW/0.6 PF), which would require larger and more expensive electrical equipment to handle the increased current.

3. Copper loss

At a low power factor, the current drawn by the load is very high, which results in high copper losses. This results in poor efficiency.

When the power factor is low, the reactive power component is high, which means that the current drawn by the load is high even though the real power being used may be relatively low. This leads to higher copper losses, which reduce the efficiency of the system. To improve the power factor and reduce copper losses, various techniques such as power factor correction using capacitors can be employed.

4. Poor voltage regulation

Voltage regulation becomes poor at low power factor. Current at a low lagging power factor causes a greater voltage drop in alternators, transformers, and transmission lines causing have low power supply at the receiving end. To keep the receiving end voltage within permissible limits, extra equipment (i.e., voltage regulators) is required that increases the overall cost of the system.

5. Low handling capacity

The handling capacity of the equipment decreases because the reactive component of the current prevents the full utilization of the installed capacity. This is because the reactive component of the current creates additional strain on the system and reduces the effective power available for useful work.

6. High cost

A consumer has to pay electricity charges for his maximum demand in KVA plus the units consumed. If the consumer does not improve the power factor, then there is an increase in the maximum KVA demand and consequently, there will be an annual loss due to demand charges.

To avoid this increase in demand charges, consumers need to improve their power factor by using power factor correction techniques, such as installing capacitors or other power factor correction equipment. By improving the power factor, consumers can reduce their apparent power demand and consequently, their maximum KVA demand which leads to lower electricity charges and annual savings.

7. Capacity reduction in the power station

A generating station is as concerned with power factor improvement as the consumer. The generators in a power station are rated in KVA but the useful output is depending upon KW output. As station output is:

𝐾𝑊 = 𝐾𝑉𝐴 × 𝐶𝑂𝑆∅

Therefore, the number of units supplied by it depends upon the power factor. The greater the power factor of the generating station, the higher the KWh it delivers to the system. This leads to the conclusion that the low power factor decreases the earning capacity of the power station.

8. Negative effect on equipment

If the power factor of a system is low, it uses more power than it needs to do the work. This can result in:

• Excessive heat is generated, which can damage or shorten the life of the equipment.
• Extra maintenance costs.
• Power loss.
• The potential for fires in extreme situations.

Low voltage conditions result in:

– Sluggish motor operation.

– Dim lights (and the resulting quality and safety problems).

All this leads to high and periodic maintenance costs.

9. Negative effect on the environment

The generation and transfer of electrical energy can severely degrade the environment. Low power factor causes electromagnetic pollution and air pollution due to the inefficiency of low power factor systems.

Improving power factor and overall electrical system efficiency can help reduce energy waste and the associated environmental impacts. This can be achieved through the use of more efficient equipment and technologies, as well as through better design and maintenance of electrical systems.

In conclusion, low power factor can lead to many disadvantages such as large conductor cross-sections, big equipment size, copper loss, poor voltage regulation, low handling capacity, high cost, capacity reduction in the power station and negative effects on equipment. Understanding the concept of power factor and its disadvantages can help industrial and commercial facility managers to improve their facility’s efficiency, reduce energy costs and prevent equipment damage. Improving power factor can lead to lower energy losses, reduced equipment size, and better voltage regulation, ultimately increasing the earning capacity of the power station and improving the overall efficiency of the system.

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