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Kwh Vs Kvar In A Power Distribution System


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#1 AB2005

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Posted 28 August 2011 - 07:30 AM

Hi Friends; ;)

In our 380V power distribution system, there is an energy analyzer installed on mains incoming just after transformer. the reading of EA is as following;

1) Kwhr = 1910000
2) Kvah = 1986000
3) Kvarh = 502500

Kwhr/Kvah reveals that the average power factor remains at 0.96. But I could not understand that only 0.04 difference of power factor (between average PF and unity PF)resulted the 502543Kvarh reactive power flow from transformer. Can any body explain it?
"Don't assume any thing, always check/ask and clear yourself".

#2 marke

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Posted 28 August 2011 - 10:42 AM

Hello AB2005

Draw a right angle triangle.

Along the base line, you have the KW
The vertical is the KVAR and the hypotenuse is the KVA

At a power factor of 0.96, the angle is arcos(0.96) = 16 degrees.

The value of the KVAR is equal to the KVA times sine(16) which comes out about right.

NOTE this assumes a constant load factor.
Where the load is variable, it is possible to accumulate KVARH, KWH and KVAH that do not add up or equal to the average.

Best regards,
Mark.




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