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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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    This is going to get very complex because you need to be sure of several different things. What exactly are your metering devices, and what is the claimed accuracy? You need to know that they really are completely power factor independent, and if so then all the numbers should be exactly equal to overall. However, no meters (even “mechanical" ones) are completely independent unless very sophisticated electronic ones which will undoubtedly give you a PF reading as well. I would not expect an accuracy of better than 0.5-1.0% for most kWh meters. The best way to measure your saving would be a KVAh meter on the PFC capacitor bank connection, or two identical kVAh meters one before and one after the PF corrector. This should give you the best measurement possible, including the metering accuracy. Measuring kWh is never going to give you the number you want with any accuracy.

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  • 0

    This is going to get very complex because you need to be sure of several different things. What exactly are your metering devices, and what is the claimed accuracy? You need to know that they really are completely power factor independent, and if so then all the numbers should be exactly equal to overall. However, no meters (even “mechanical" ones) are completely independent unless very sophisticated electronic ones which will undoubtedly give you a PF reading as well. I would not expect an accuracy of better than 0.5-1.0% for most kWh meters. The best way to measure your saving would be a KVAh meter on the PFC capacitor bank connection, or two identical kVAh meters one before and one after the PF corrector. This should give you the best measurement possible, including the metering accuracy. Measuring kWh is never going to give you the number you want with any accuracy.

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