wrote:

I'm clearly trying to discover whether the power factor I measure is
affected in any way by the electricity network. If you put a purely

IIUC, it is not effected by the network as such, although it may be
affected by other users of it.

resistive load across the supply coming into your house, are you
guaranteed to measure no phase difference between the voltage and the
current? If the phase difference is zero, then the power factor of
your supply is 1.

With purely resistive loads then it is not an issue. For loads with a
reactive component then the reactive component will typically be the
major influence on the power factor. However the quality of the waveform
that you are supplied with can further influence it.

There's a whole load of stuff on the web about the lengths the
National Grid go to power factor correct their supply. Perhaps you
should ring them to tell them they are wasting their time?

They go to some effort to mitigate the effects their users have on the
supply. A big industrial user (or the cumulative effect of many smaller
ones) pulling large currents from the supply that are not phase aligned
with the voltage, can end up distorting the supply waveform. This leaves
the waveform non sinusoidal and hence introduces other frequency
components into it. These will interact with the reactive elements of
any load differently than would a plain 50Hz supply.


--
Cheers,

John.

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