wrote:
On 6 Oct, 19:52, Adrian C wrote:

Power factor of the supply? What's that then?



It's something the National Grid are obliged to keep within certain
limits: 0.85 lagging - 0.95 leading.

Well sort of...

The concept of power factor only really has any meaning when you know
the characteristics of the load. With a resistive one, the power factor
is 1 regardless of the supply.

What the grid are obliged to do is provide a stable supply, and ensure
that the required true power output of the generating plant is available
to the grid. Obviously this would not be the case if capacity on the
network is going to be absorbed by large reactive currents flowing
around it. They also need to ensure local voltage stabilisation.

The limits you specify above are limits for the *load*. i.e. they must
meet certain performance criteria when the connected load lies within
those limits. With applied loads outside of these limits they are not
required to achieve the same standards.

A distribution system itself will also have a number of reactive
components within it, like the cables (transmission line effects), and
transformers. The effects of these will also need to be compensated for.




--
Cheers,

John.

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