Power plants are rated in MW because this value reflects the real, useful power they produce, while MVA accounts for both real and reactive power.
The power factor plays a role in determining how much of the apparent power (MVA) can actually be used as real power (MW).
1) Real Power (MW)
Represents the actual usable power produced by the plant.
MW indicates the power that performs useful work (lighting, machinery, etc.).
This is the power consumed by end users, which is why power plants are rated in MW.
2) Reactive Power (MVAr)
Power that doesn’t perform useful work but is essential for maintaining voltage levels in the electrical system.
This is the component of power that supports the magnetic and electric fields in inductive and capacitive loads.
3) Apparent Power (MVA)
The combination of real power (MW) and reactive power (MVAr).
MVA is the total power delivered, but it doesn’t fully represent how much of it can be used for actual work.
Formula: Apparent Power (S) = √(MW² + MVAr²)
and is affected by the power factor.
4) Power Factor
Power factor (PF) is the ratio of real power (MW) to apparent power (MVA).
Formula: Power Factor (PF) = MW/MVA.
A higher power factor (closer to 1) means more of the apparent power is being used as real power.
In an ideal condition, if PF = 1, MW = MVA (no reactive power), but in reality, most systems have a power factor below 1 due to inductive loads.
Why MW Ratings consider?
Power plants are rated in MW because the purpose of the plant is to supply real power (the power that consumers can use).
Power factor impacts how efficiently the power can be utilized, but the rating in MW reflects the capacity to generate work-producing energy, which is more meaningful than the total apparent power (MVA).
MVA includes both real and reactive components, but power plants are not rated for reactive power output as their primary function.
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