Reactive power loss

[mivey]

And thus not reactive losses as you stated.
QED.

QED over there perhaps, not here.

 

[Besoeker]

Not just through "a" resistive element but through resistive elements (plural), including the transformer R1, feeder R, and source R.

Yes it is part of the current flowing through those other elements but it is the only current flowing through the resistive element representing the core. Call it Rm, since that's term usually used on the induction motor equivalent circuit which is very similar. Core loss then becomes Ic^2*Rm.

 

[Besoeker]

QED over there perhaps, not here.

The physics is universal. Contradictory statements like this do you no favors:

Your post #3 - In delivering reactive power and receiving reactive power, this extra "I" running back and forth heats up the wire and creates real losses. That is reactive losses.

My post #15 - doesn't make those I^2*R being anything other than resistive.

Your post #36 - Of course they are resistive.

 

[mivey]

The physics is universal. Contradictory statements like this do you no favors:

Your post #3 - In delivering reactive power and receiving reactive power, this extra "I" running back and forth heats up the wire and creates real losses. That is reactive losses.

My post #15 - doesn't make those I^2*R being anything other than resistive.

Your post #36 - Of course they are resistive.

I will concede that it is my use of loose terminology at best. To be precise, "reactive power loss" is the difference in var delivered vs var received. I'm trying to parse out the consumption of real energy due to the delivery of reactive power, specifically the energy consumption that can be reduced by corrective measures. Perhaps there is no short-hand way of saying it and I have no doubt that my use of terminology has been tainted by years of working with slang, etc.

 

[mivey]

Yes it is part of the current flowing through those other elements but it is the only current flowing through the resistive element representing the core. Call it Rm, since that's term usually used on the induction motor equivalent circuit which is very similar. Core loss then becomes Ic^2*Rm.

And if I am looking at system losses for a collection of transformers, I will reduce my system losses by more than just the loss reduction in the core. As far as the system is concerned, installing more efficient transformers brings me more value than that noted at the "core terminals" (Ic^2 * Rm).

Same goes for reducing other reactive loads out on the system. I am grouping that energy savings in with reactive load control. That is different than energy savings I might get through what we just call plain-old "load control" (an actual reduction in energy consumption by the end-user). Find whatever term/phrase makes you happy when separating these two types of energy savings.

 

[WastefulMiser]

So in conclusion I was correct in questioning the misnomer "reactive power loss".

 

[mivey]

So in conclusion I was correct in questioning the misnomer "reactive power loss".

It is certainly worth clarifying what is meant. In the precise use of the term, it is not talking about a loss of consumption but is comparing the var delivered vs the var received.

On the other hand, if you mean the consumption loss caused by reactive loads, then it a resistive loss caused by the extra current needed by reactive loads.

Which one did you mean?

 

[WastefulMiser]

It is certainly worth clarifying what is meant. In the precise use of the term, it is not talking about a loss of consumption but is comparing the var delivered vs the var received.

On the other hand, if you mean the consumption loss caused by reactive loads, then it a resistive loss caused by the extra current needed by reactive loads.

Which one did you mean?

Hmm. The formatter or possibly the latormer.

Actually, I was just wondering how reactive power was lost.

 

[mivey]

Hmm. The formatter or possibly the latormer.

Actually, I was just wondering how reactive power was lost.

Former: It is not "lost" in the same sense as we have heat dissipated by resistive losses. At the source, the generator delivers a certain amount of vars. At the load, the system line inductance, capacitance, and other parasitic var loads have accounted for some of the vars from the generator and the load only needs a portion of the vars generated. So the vars generated is different from vars at the load. That is the classic meaning of "reactive power losses". In a perfect delivery system, this power is not actually "lost" but is temporarily stored in the reactive parts of the system until it is returned 1/2 cycle later.

Latter: The vars that are moved up and down the line generate extra heat because the current associated with it must be pushed through the line resistance and results in heat being dissipated. So, the reactive load causes real losses.

Real load: The generator also delivers W. The current associated with the load W must also be pushed through the line resistance and results in heat being dissipated. This is real losses associated with real load.

So the generator delivers vars:
delivered vars = vars for the metered load + vars for the parasitic loads
and the "reactive power losses" = vars for the parasitic loads

The generator also delivers watts:
delivered watts = watts consumed by load + watt losses associated with real power delivery + watt losses associated with reactive power delivery/receipt

and you will sometimes hear the "watt losses associated with reactive power delivery/receipt" called "reactive losses"

 

[Besoeker]

To be precise, "reactive power loss" is the difference in var delivered vs var received.

Then perhaps you could clarify precisely what you consider to be the difference between delivered and received?
When our stores receives goods in, they are usually accompanied by a delivery note. The point to which to goods are delivered is the point at which they are received.

 

[mivey]

Then perhaps you could clarify precisely what you consider to be the difference between delivered and received?
When our stores receives goods in, they are usually accompanied by a delivery note. The point to which to goods are delivered is the point at which they are received.

Then consider what would happen if the delivery route went through an area controlled by the mob where everybody wants their "cut". The power system takes a "cut" out of the vars that were delivered and what is sent on one end is not the same as what is received on the other. In other words, the instantaneous vars on the sending end of a circuit (delivered) is different from the instantaneous vars on the receiving end of a circuit (received).

The instantaneous power on either end is given by the voltage and current at the ends and is p = v*i = Vm*Im*cos(ωt)*cos(ωt−θ). Thus, the instantaneous real power is 0.5*Vm*Im*cos(θ)*(1+cos(2ωt)) and the instantaneous reactive power is 0.5*Vm*Im*sin(θ)*sin(2ωt). We can see by these expressions that the real power is centered around some average value (a consumption loss) and the reactive power is centered around zero (not a consumption loss like in the real power case).

For a power system, we define the reactive power in terms of the bus voltage. Using a Pi bus model with a series resistance and inductance connecting two voltages with parallel capacitances, we can use the sending and receiving end voltage phasors and current phasors to find our sending end (delivered) and receiving end (received) reactive powers.

We use the voltage times the complex conjugate of current to get the following (neglecting the resistance for this calculation because of the relatively small impact) in terms of the sending end (delivered) voltage and the receiving end voltage (using phasors Vs and Vr):
Sending End (Delivered) Reactive Power = (Vs^2-Vs*Vr*cos(θ))/X_ind - (Vs^2)/X_cap
Receiving End Reactive Power = (-Vr^2+Vs*Vr*cos(θ))/X_ind + (Vr^2)/X_cap

Using these two equations in a power system we find the reactive power loss is the difference in the delivered (sent) vs received reactive power.

This is not the same as the energy loss caused by the transmission and storage of the reactive power. As I said, call that whatever makes you happy.