Analog dynamic range, accuracy and number of bits

The point is that the harmonics can dominate the power. Trig doesn't help except for waveforms that are adequately close to sinusoidal, because all the harmonics will in general have different phases.

Cheers

Phil Hobbs

Sure. All of my meters can measure both directions, and some have separate KWH registers for the two directions. But in most applications, power only flows one way, and negative means the CT is backwards from the installation drawing.

If you want to do that, nobody's going to arrest you.

There seem to be (at least) two industry conventions for signed PF. See the GE link I posted recently.

There is widespread disagreement on what PF means in the four quadrants. Some eminent sources declare it to be undefined for negative power, or for asymmetric phases, or for nonsinusoidal waveforms. If you sell an instrument, you should state your definitions in the manual.

The voltage and current waveforms are the whole story. The confusion is turning them into words.

If the line voltage stays sinusoidal, there is no true power in the current harmonics. But lots of wire losses, which will annoy the power company.

There have been office fires from all those old non-PFC PCs frying the neutral wires in partition wiring. The wiring was sized assuming that phase currents in neutral would mostly balance, but they don't for the spikes from switching power supplies.

You miss the point. As long as P is less than VA you can calculate phi. It may not relate two sine waves, but it will represent the same information as P/VA.

Rick

So then you are agreeing that power can be negative. The fact that your meters are incapable of representing this as a negative value is of no consequence to the concept of power.

The definition of PF = P/VA seems pretty clear to me. The IEEE quote says power factor is only defined when power flows to the load.

Rick

All the meters that I've done can measure positive and negative power; it's actually harder not to. Some, like apartment submeters, can only accumulate positive KWHs. To my knowledge, no apartments at Battery Park City sell power back to the utility.

Whether power is + or - depends on where you are standing and what direction you are facing. You declare your convention and direction, then you measure.

Sometimes people have to go ahead and define it the other way. Or just redefine who is the generator and who is the load.

That sounds circular to me. Do it if you need to.

the power supply frequency is not fixed, but varies, doing the sampling at a matching variable rate would complicate the arithmetic for no benefit that I can see.

That's what it says,

It's possible tm misremembered or miswrote

what if the current is neither leading nor lagging?

say, a bridge rectifier driving a resistor in series with a zener diode. (or a long series chain of LEDs)

really, you measured using a scale where 0.9 is closer to -0.9 than

would't it make more sense to measure VAR ?

Is that current leading voltage, or voltage leading current?

If you have a non-sinusoidal current that is time symmetric about the voltage peak, you can have a PF below 1 but have no reason to call it leading or lagging. Another dilemma of words but not of waveforms. Maybe that's another reason that some people state that PF is undefined for non-sine loads.

Bottom line, there's too little information in one number and a few words to define two waveforms.

An inductive load is considered to have a positive PF by most people who use the sign convention. The current waveform lags, namely peaks later than voltage in time.

don't

customers

correctors

bigger

loop

Aw poor JL; doesn't like the fact that there are such a thing as standards. You would self-destruct in a highly regulated environment.

?-)

anything

in

that

systems,

more

and

Normal electricians do not work on 12.47 kV equipment, nor do they specify them. That you seem to be missing that is telling. I specify such equipment and work with the electric service provider to integrate my systems with theirs properly.

YMMV

?-)

You

Remote turn-on / turn-off. Time of usage rate billing. Undoubtedly more.

?-)

So, a leading current is considered positive. I don't want to know about the sign convention (positive/negative), tell me about the leading/lagging convention.

Repeating: Is that current leading voltage, or voltage leading current?

To clarify further, is current leading voltage considered leading PF? Or... ?