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System Benefits of Power Factor Improvement

What is the significance of power factor improvement in power systems?
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Answer & Explanation
Correct AnswerD. It minimizes the reactive power burden on generators and transmission equipment.

Quick Explanation

D — It minimizes the reactive power burden on generators and transmission equipment. Local compensation reduces the reactive current carried upstream.

Formula / Key Relation

S = P/cos φ
IL = P/(√3 VLcos φ)
Qcomp = P(tan φ1 − tan φ2)

Detailed Explanation

Correct answer: D — It minimizes the reactive power burden on generators and transmission equipment.

Why low power factor burdens the network

An inductive load draws active power P to perform useful work and reactive power Q to maintain its electromagnetic fields. The supply equipment must carry the resulting apparent power S, even though reactive power does not represent net energy converted into useful work over a full AC cycle.

S = √(P² + Q²)
Power factor = P/S

Power-factor improvement supplies part of the reactive requirement locally, for example through a capacitor bank. This reduces the net reactive power demanded from the upstream network while the useful active-power requirement can remain unchanged.

Effect on current and equipment capacity

IL = P/(√3 VLcos φ)

At fixed active power and voltage, a higher power factor means a smaller line current. The lower current reduces I²R losses, reduces the current-related voltage drop and releases some of the kVA capacity of generators, transformers and lines.

For illustration, a 100 kW load requires 125 kVA at 0.8 power factor but only about 105.3 kVA at 0.95 power factor. Its active-power requirement remains 100 kW; the supply carries less apparent power because the reactive component is smaller. This is the meaning of reducing the reactive-power burden in option D. Compensation should match the load rather than create unnecessary leading VARs.

Quick Trick

PF ↑ → current ↓ → losses and kVA burden ↓.

Why Other Options Are Wrong

A transients are not the purpose. B power-factor improvement increases usable system capacity rather than decreasing it. C it tends to reduce, not increase, transmission cost for a required power transfer. D correctly states the reactive-burden benefit.

Common Mistake

Saying power-factor correction reduces the load’s real kW demand. It mainly reduces reactive demand and line current for the same useful real power.

Exam Tip

Fixed kW: current is inversely proportional to power factor.

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