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Importance of reactive power
Questions on the importance of reactive power?

We read a lot of things in our schools for reactive power which is useless power and to compensate this power there are lot of methods.
When i came in actual work in industry, i came to know from our seniors and manuals that reactive power is not fully useless. We need reactive power in system. Is it true ?

When we talk about var compensator what are they doing ?

my third question is, when the var compensator is not connected to system, why the line voltage drops?

What is the acceptable range of voltage drop in primary of the transformer when the load on the secondary side changes from no load to full load?

These are some of the questions roaming around in my mind..please help...

Ask yourself this question? If it's "useless" power, why does it have to be compensated for, or for that matter, why does it even have to be monitored?

Some people say it's like foam on beer: it's just there but it doesn't do anything.

A former colleague used to say that the foam on a glass of beer (the "head") does indeed tell you something. It tells you the beer is not flat, and flat beer is not good! Of course, we don't want too much foam on our beer, but we would like to know that the beer is not flat either, so some small amount of foam (head) is desirable.

The *effect* of reactive current is to shift the voltage- and current sine waves out of phase with each other, which can have very serious consequences for AC systems if left unchecked. So, induction motors and flourescent lighting (the two biggest causes for reactive current flow and its effects) must be "countered", as it were, to keep the voltage- and current sine waves closer to being in phase with each other, which is the ideal way for an AC system to be operated (most efficient). That's why there are various methods for compensating for reactive current.

It's also generally not good mechanically for generators to have high reactive currents (we have to watch how we describe this phenomenon lest we encur wrath; "reactive power" is a no-no around here).

My reaction to your last statement/question would be that a properly monitored and controlled system would not see very much change in transformer voltages (primary or secondary) if the reactive current is being properly controlled or maintained at a fairly stable level. Now, creating reactive current with a generator does reduce, somewhat, it's ability to produce real power (watts), but there's no such thing as a free lunch, mate!

1 out of 1 members thought this post was helpful...

CSA... Drill certainly does not have to be concerned about enduring (my) wrath but, instead should fear your ignorance about the term "reactive power!"

Drill, just contact me for my paper, "The Physics of... Armature Reaction"! CSA hasn't read it yet, so I'm still puzzled about why he shuns such enlightenment!

Regards, Phil Corso (cepsicon [at] aol [dot] com)

0 out of 1 members thought this post was helpful...


I purposely didn't respond to this thread immediately because I was hoping you would. The fact that you immediately responded after I did speaks volumes about your agenda on this forum. You rose to the bait exactly as expected.

I have read many texts and Internet citations that refer to reactive power, and certainly every power plant discussion I have ever had about VArs and power factor had someone using the term reactive power. I believe the reactive capability curves provided by most generator manufacturers plot real power (watts) against reactive power (VArs).

I have given your position on reactive power a great deal of consideration over the years. I have obtained a copy of your paper and read through it, several times. I don't believe it really made a case for or against the use of the term reactive power, nor did it really address the issue of armature reaction by clearly explaining the phenomenon.

Yours is the only explanation of or admonition against the use of the term reactive power I have ever heard, in more than 30 years. When people talk about current flow in a wire, there is conventional flow and electron flow, which are mutually exclusive yet people still use the two terms to successfully describe what's happening or to analyze circuits.

So, you seem to be on a personal, one-man crusade against the use of the term reactive power. I would like to understand even if the term is incorrect in the strict physical sense what you hope people will learn or gain by understanding that it's not a physically correct description?

What term will you have the world use to describe the losses associated with VArs?

1 out of 1 members thought this post was helpful...

CSA... thank you for your kind words.

Now, for all to see, attached are two paragraphs
from the paper that clearly present my position, which is, "reactive power", an oxy-moron (see List Topic, # 1026236550, "The Physics of... Electric Power") shouldn't be used, but instead, kVAr, should:

This paper has four goals:

(a) Describe Armature-Reaction more clearly than hath been presented heretofore (I love lawyer-speak.)

(b) Dispel doubt, misinformation, and misunderstanding that have cropped up in related A-List topics.

(c) Reduce animosity (just kidding) about questionable or ambiguous jargon.

(d) Eliminate myths, misnomers, and omissions.
Adjectives describing Armature-Reaction are plentiful, some even inventive, but most miss the point! Here are some pairs that were culled from A-List and Off-List responses: adds-subtracts; additive-subtractive; augments-negates; crowded-expanded; decreases-increases; fights-gives up; overcomes-replaces; overtakes-replenishes; magnetize-demagnetize; support-oppose; strengthen-weaken; and swell-shrink. There have been and certainly will be others! Thus far, no-one has used adjectives such as: encourage; discourage; thwart; or tweak! I hope this paper will curtail (hmm, a synonym I hadn't noticed earlier) the seemingly growing list of adjectives."

"In my opinion a synchronous generator does not absorb, or consume, or import, or receive, or take-in, or produce, reactive power. Then, for consistency, the author suggests that the terms listed above, as well as reactive power, be eliminated. Instead, the expression that the generator delivers or exports lagging or leading kVAr, should be substituted! (NOTE: this recommendation does not preclude anyone from using terms with which they are familiar!)"

Lighten up, CSA!

Please to have you as a penpan, Phil

PS: Yes, I admit to having an "agenda!" Simply put, this forum should used to inform, not confuse participants.


Quoting here:

"...In my [your] opinion a synchronous generator does not absorb, or consume, or ..."

Quoting again:

"...(NOTE: this recommendation does not preclude anyone from using terms with which they are familiar!)..."

Those are your words, Phil. Why didn't you correct the originator of this post for using 'reactive power' if that's the way you feel? Why didn't you respond to his question with your admonishment not to use the term, but rather to use kVAr?

My response specifically did not use the term reactive power, and I mentioned that the use might be frowned upon.

Was there anything in my response that was not technically correct or was misleading? (I specifically changed every initial usage of 'reactive power' to 'reactive current'.) I didn't talk at all about producing or consuming, abosrbing or generating, reactive power. I referred to the effects of reactive current on an AC system and that when countered the AC system runs more efficiently. Was that incorrect or misleading in any way?

I stick by my original statement: You are the only person I have ever heard decry the use of the term 'reactive power'. It's an accepted industry term, used in most texts and handbooks, and as such should be "allowed" to be used here on by anyone.

You still have not answered the question of what you hope for people to gain from not using the term. Is there some principle that you want people to learn that will make the whole subject clearer? Something that will cause a sudden understanding that was just beyond grasp, an "Ah, hah!" moment?

If you're not going to ask or criticize others for using the term, and you're going to wait to pounce on one person for doing so in response to someone's initial use of the term, please just refrain from posting altogether.

Isn't use of the word 'ignorance' a little heavy? (Not to mention all those aggressive exclamation points.) If you can find fault with my explanation, please articulate the errors; I'm always interested in learning anything from anyone I can.

However, if you can't, an apology is in order for using 'ignorance' when referring to the response.

Penpan? I can't find that in my Oxford's Dictionary.