# Why is a Power Plant Capacity Rated in MW and not in MVA?

## Why is the Rating of a Power Plant Capacity Expressed in MW instead of MVA?

For the following reasons, a power plant capacity rating may be expressed in megawatts (MW) instead of megavolt-amperes (MVA).

In a generating station, the prime mover (turbine) generates only and only active power in Watts. A generator then converts the mechanical power into electrical energy i.e. Volt x Amps x Power factor which is further transmit and distribute in a typical power system scheme. That’s why we express the rating of a a power plant capacity in MW instead of MVA. It means no matter how large your generator is, but it depends on the capacity of the engine (prime mover / turbine) i.e. a 50 MW turbine connected to a 90MVA alternator (which generates both active and reactive power) in a power plant will generate only 50MW at full load.

In short, a power plant rating is specified in terms of prime mover / turbine (turbine rating may be seen by nameplate rating which is in MW or Horsepower (HP) not in MVA) and not by the alternator set coupled to it.

Another thing is that, electric power companies charge their consumer for kVA (electricity bill) while they generate kW (or MW) at the power station (power plant).They penalize their consumer for low power factor because they are not responsible for low power factor and kVA but you. Moreover, in a power plant, power factor is 1 therefore MW is equal to MVA …… (MW = MVA x P.F).

Another interesting and funny answer by one of our Facebook page fan…“Power House means house of the Power, and we know that the unit of power is Watt. That’s why we rated a power plant capacity in MW and not in MVA”.

Related Posts:

### Electrical Technology

1. Gaurav Kumar says:

sorry but MW = MWA x Cosφ(Power Factor)

1. Electrical Technology says:

Thanks for correction…!

2. TARIQ MUFTI says:

MW=MVA x power factor

2. Jugraj Singh dewda says:

sir plz sent me iti 2014 janury paper my e-mail id:jugrajsinghdewda@gmail.com

3. Jugraj Singh dewda says:

plz sent me iti janury exam paper my e-mail id:jugrajsinghdewda@gmail.com

4. Selva Kumar says:

thanks….

5. mv Waaran says:

we cant say 90MVA ALTERNATOR WITH 50 MW PRODUCES 50 MW….. Generation unit is depend on the generator construction like pole, winding and its size all of those. bcz, it only decides the induced emf. and also speed is one of the part only but not fully depend on that turbine speed. so that is not a valid point to make mw rating. Generating stations are normally rated as Mw bcz station has to give

6. jahangeer khan says:

sir plz send me. why we use scada in power houes for monitorin. what the problem in the old system

sir tell me ur electricle book name or i want to meet u

8. Omid Miakhail says:

9. MATHUKIYA DHAVAL A says:

sir,,plz give me ..name of latest @ more suitabel
SCADA software use in power house….

1. Electrical Technology says:

10. Mohammed AL-Tamimi says:

i am power electronic engineer

11. khan says:

if one power plant is 50MW, and have ONLY one step up transformer 50/60 MVA, so its is sufficient to transfer power to power purchaser ?

12. Patrin says:

If turbine does not supply any reactive power so where does reactive power com from!

13. Abhijit Maity says:

wow, informative

14. Thomas Gondo says:

What would be the total power generated by a 100 MW turbine to a 50 MWA alternator?

15. Nicholas Akpan says:

very interesting

Check Also
Close