We have gone past unity, possibly leading by 10% - 20%Is there any harm in this or should we be correcting it back to 90% to100%? The plant contains mostly transformers and HID lights.There are a few VSD motor starters but a very small proportion of theload.To send me e-mail remove the sevens from my address.Chrisd

Please provide additional details such as:What leads (pun unintended :-] ) you to believe you do in fact have aleading power factor.What instrumentation was used for quantification, and who wasoperating/interpreting the resulting data?What you describe is a rather unusual situation, and with the equipmentlisted, unless there is equipment we are unaware of, the power factor shouldbe approximately what you list except lagging.Louis

What are the effects of a leading power factor?

Aug 24, 2004 44 Replies

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Don Kelly 21 years ago

--------- The demand meter that I saw (and tested once as a student 50 years ago) ) was not a modified watthour meter. It definitely did not read kVAH or kVARH. It was a Sangamo(at least I remember the name if little else) thermal demand meter which used a thermal element.There is an incomplete as to principles reference to it

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date of invention appears incorrect as they were available in Canada in the '50s. The reference above indicates one reason for their disappearance in most places although they still seem to be in the curricula in some tech schools. The other reason is that better methods are available for less money. These would used on small commercial loads.

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s falke 21 years ago

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The date of invention appears incorrect as they were available in Canada in

In the late 1980s-early 1990s, Messrs. Arseneau and Filipski of the Canadian National Research Council did original work on revenue metering to drive application of the digital *kVA-demand* function. They used field-captured V and I waveforms {up to ~48% Ithd} to extensively compare theoretical to actual measurement.

?s falke

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John Phillips 21 years ago

We used as, I recall, Sangamo thermal converters as transducers that produced a millivoltage output that was proportional to watts or vars for real time measurement or to drive strip chart recorders. Their accuracy was though much poorer than watthour meters. It is not clear if these were similar devices.

Regards,

John Phillips

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Don Kelly 21 years ago

------ Again - going by recall- the meter was fairly large- larger than a typical single phase watthour meter and with a dial which would have pointer/scale of the size of a typical switchboard meter. Output was purely visual in that a pointer drove another pointer to register the maximum visually. I really wish that I had more information but it was a long time ago and any references that I had for this have been long gone.

cheers,

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Ben Miller 21 years ago

I agree. Demand meters typically look at a 15 or 30-minute window, depending on the utility, and it takes a good portion of that time before a steady load will register 100% as the peak, although it will register some percentage for shorter periods. This is natural with the thermal delay type demand meters, but of course with solid-state meters they can program them to do whatever they want.

Ben Miller

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