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Power factor (again)

Johno12345

Sorry for yet another question on this topic.

 

I have got sub metering installed on all outgoing submains, I also have a meter on the incoming main

 

Between the main meter and sub meters, I have my power factor correction

 

over a week, I'm getting about 1,500kWh of difference, the sub meters total being higher by that amount compared to the incomer meter.

 

I'd like to say that the power factor correction has effectively saved that number of kWh, is that correct?

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    Hmm possibly. I presume this is a fraction of the total - it sounds like a lot, but I do know you have a big site.

    Depends how the sub-metering is working.

    If it is measuring KVA, yes,  if KW no.

    Most official power meters are more or less power factor agnostic - that is to say the reading does not take RMS amps and multiplicity by RMS volts, (that would be kVA) but also allows for the phase slip type of power factor. (kW)

    This is done in electronics these days, where the spot current is multiplied by the spot voltage at perhaps a couple of  hundred sample points  spread more or less uniformly over the main cycle, and then an average deduced. For part of the cycle this has a positive voltage multiplied by a negative current and that is the power returned due to the phase shifts.

    In the older units it was a mechanical thing where the forces on the counter were the product of a magnetic field generated proportional to the current and another electromagnet proportional to the voltage. The effect for nice clean sinewaves is the same, some noisy switching waveforms can confuse the sampler kind.

     

    Mike

     

     

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  • 0

    Hmm possibly. I presume this is a fraction of the total - it sounds like a lot, but I do know you have a big site.

    Depends how the sub-metering is working.

    If it is measuring KVA, yes,  if KW no.

    Most official power meters are more or less power factor agnostic - that is to say the reading does not take RMS amps and multiplicity by RMS volts, (that would be kVA) but also allows for the phase slip type of power factor. (kW)

    This is done in electronics these days, where the spot current is multiplied by the spot voltage at perhaps a couple of  hundred sample points  spread more or less uniformly over the main cycle, and then an average deduced. For part of the cycle this has a positive voltage multiplied by a negative current and that is the power returned due to the phase shifts.

    In the older units it was a mechanical thing where the forces on the counter were the product of a magnetic field generated proportional to the current and another electromagnet proportional to the voltage. The effect for nice clean sinewaves is the same, some noisy switching waveforms can confuse the sampler kind.

     

    Mike

     

     

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