Harmonic affects

[PowerQualityDoctor]

Personally you have been coming across as disingenuous with your claims you have nothing to sell.

I did not say that I have nothing to sell. I said that I do not sell harmonic filtration solution, services or even consulting.

Accuracy is probably characteristic of engineers.

 

[mivey]

I live with my eyes open and am not blinded by a few letters at the end of a persons name.

Unless those letters happen to match your last name (wife, children, etc). Love is blind, right? :grin:

 

[don_resqcapt19]

... and have a lot of experience in seeing such places...

If you are in the power quality business, I would expect that you would see a number of problems...you would not normally see a job site unless they were experiencing problems of some sort, however as a percentage of the total number of electrical installations, the ones with harmonic problems would be very small.

As far as my mistrust of the industry "sales" engineers, a very large part of it can be traced to the extreme amount of misinformation that was provided on the part of the breaker companies to get the AFCIs in to the code. Some of what they said in the original ROPs and ROCs were outright lies. As a result of this I no longer trust any information from anyone who tells me I have a problem and I can sell you something to fix that problem. Almost all of the information about harmonic issues falls into this category.

 

[Besoeker]

My understanding is that one thing we won't see on a single phase system is the overloaded neutral conductors as a result of the harmonic currents that are additive in 3 phase systems.

I agree.
.....

 

[mivey]

If you are in the power quality business, I would expect that you would see a number of problems...you would not normally see a job site unless they were experiencing problems of some sort, however as a percentage of the total number of electrical installations, the ones with harmonic problems would be very small.

As far as my mistrust of the industry "sales" engineers, a very large part of it can be traced to the extreme amount of misinformation that was provided on the part of the breaker companies to get the AFCIs in to the code. Some of what they said in the original ROPs and ROCs were outright lies. As a result of this I no longer trust any information from anyone who tells me I have a problem and I can sell you something to fix that problem. Almost all of the information about harmonic issues falls into this category.

But no need to stay dog-bit. I agree we see a lot of unscrupulous goings-on but we should still try to search for the true value in people. At least when it is just postings here, we are not at immediate risk. We can afford to be a little more patient here until we can get enough info to start making judgments. I'm not really sure that in this type of forum if we could ever get all the details. Even in life, isn't there a saying about if we had all the information we needed to make a decision that it would not be a decision but a forgone conclusion?

Naturally, you have to be more defensive on the job and can't afford to be so open. Here we can judge what is currently posted, and try not to be biased by those that have come before. I'm not pontificating as I face the same things myself and often forget.

Anyway, back to our regularly-scheduled programming.

 

[Besoeker]

Almost all of the information about harmonic issues falls into this category.

Maybe from some sources.
I need to be pragmatic about harmonics, in fact engineering generally.
You may already know that my background is power electronics. This has been mainly, but not exclusively, in the field of variable speed drives.
Even from the early drive days, post Ward-Leonard, harmonics has always been a known concern - I have a copy of a 1948 paper that deals with the subject in considerable detail and the mathematical derivations are still relevant.

Thus, for me, harmonic issues started out as a consequence of what I was doing in my field. I have to provide information on harmonics even at the bid stage to show that what we are offering complied with requirements. Sometimes this means including harmonic mitigation measures and/or hardware in order to meet those requirements. It is not in my interests to make the harmonic issues worse than they are. That would result in higher costs and put us at something of a disadvantage against competitors.

So, you see, not everyone with an interest in harmonics wants to peddle the excrement of Taurus.

 

[don_resqcapt19]

I looking at the total number of electrical installations, what percentage actually have problems that are caused by harmonics?

Yes the math and the theory say we should have problems caused by harmonics, but how often do we really have such problems. I do a lot of work at an industrial facility with a load of about 10 megawatts. There are a couple of hundred drives ranging from 1 hp to 1750 hp. About 15 of these drives are for motors 500 hp and larger. In addition most of the lighting is HID. Should we expect problems here?

The company had a power quality study done just to see if there were hidden issues....none were found.

 

[StephenSDH]

There are a couple of hundred drives ranging from 1 hp to 1750 hp. About 15 of these drives are for motors 500 hp and larger. In addition most of the lighting is HID. Should we expect problems here?

I bet alot of care was given to selecting the front end of those drives. Alot of material and engineering went into producing low THD lighting so you don't have issues. The harmonics are there. I think it is important to understand, but alot of the preventative work has already been done at the manufacturing stage.

 

[__dan]

Trolling

Trolling

It's very easy to be insulted by reading both something intended and something that is not there.

If I pour water into your hands, can you squeeze the water ???

...

Now, if I give you water and the equipment of your choosing, can you compress the water?

Did you give different answers to the two questions and why ???

Were you insulted by the questions, did I imply a lack of subject matter knowledge ?

There is no right or wrong answer to the questions. What I am looking for is a simple the test, conditioning and type of mind. Does the subject matter interest you sufficiently that you have an existing quantitative knowledge, is your interest such that you immediately googled the properties of water ???

If I draw for you a low pass filter, a high pass filter, can you identify them on sight ? Is there an intended insult in the question ? Please display for me your type of mind, that is my inquiry.

 

[don_resqcapt19]

I bet alot of care was given to selecting the front end of those drives. Alot of material and engineering went into producing low THD lighting so you don't have issues. The harmonics are there. I think it is important to understand, but alot of the preventative work has already been done at the manufacturing stage.

They are nothing more than standard parts...the same ones that many people claim to be the cause of these "problems". With very few exceptions these drives do not have line or load side reactors or anything else to limit the "problems".

As far as the design of the equipment limiting the problem, that is how it should be. The manufacturers should be responsible to prevent the problem from leaving their equipment, and if it does, they should be responsible for the changes to the electrical system that may be required to protect the electrical system from the equipment.

 

[brian john]

Brian, I don't have much of a life. :grin::grin::grin:

Roger

I'll bet on the big brain also

 

[StephenSDH]

With very few exceptions these drives do not have line or load side reactors or anything else to limit the "problems".

Most double digit HP drives that I have seen has a DC Link Choke. As far as harmonics are concerned it is no different then having line reactors external to the drive. We usually add external line reactors anyways to protect the drive from transients, plus it further reduces harmonics/noise. As a system integrator we can't risk having issues and being called back, so we usually add line reactors preventively. Allen Bradley strongly recommends them for their Kinetix Servo Drives.

As far as the design of the equipment limiting the problem, that is how it should be. The manufacturers should be responsible to prevent the problem from leaving their equipment, and if it does, they should be responsible for the changes to the electrical system that may be required to protect the electrical system from the equipment.

I agree, but manufactures don't care. They don't know where their equipment is being installed or what other equipment is at the plant. They advertise it in their spec sheets and it is your job to do your due diligence before ordering.

This is why for Besoeker, harmonics are make/break. He needs to provide custom equipment for a customer that will operate with-in specifications so the customer doesn't have long term issues.

As far as additive current on the neutral, I haven't seen it as an issue, and don't think I ever will. If anything it makes that lazy neutral do a little work instead of just watching the phase conductors carry the load. Overloading the neutral isn't the only place harmonics can cause issues. Harmonics show up on audio speakers, analog io, capacitor banks, high speed counters, telephone, communications lines, efficiency losses in transformers. If you build custom equipment you have to be concerned about it.

 

[PowerQualityDoctor]

My non scientific statistics shows that the forum moderators has one opinion, while all other posts have the opposite opinion.

What does it mean? Is it due to their experience with discussions with sales people, or maybe the forum selects its moderator according to their approach?

 

[Besoeker]

I looking at the total number of electrical installations, what percentage actually have problems that are caused by harmonics?

I don't know. Let me reiterate what I said in a number of posts:

Post #21
Except where there is a fairly immediate and dramatic effect, I think that the deleterious effects of harmonics are likely to go under recorded.

Yes the math and the theory say we should have problems caused by harmonics,

Two different issues there. Mathematics gives us the means of calculating the magnitudes of the harmonics. It is an engineering call as to whether these are, or could be, a problem. Not should be.

And there are two different disciplines.
Much of engineering requires mathematics to solve problems but is is just a tool and only part of the solution.

One lecturer I had explained it as three steps.
Express the problem in mathematics.
Solve the mathematics problem
Interpret the result.

Very important, that third step.

I do a lot of work at an industrial facility with a load of about 10 megawatts. There are a couple of hundred drives ranging from 1 hp to 1750 hp. About 15 of these drives are for motors 500 hp and larger. In addition most of the lighting is HID. Should we expect problems here?

The company had a power quality study done just to see if there were hidden issues....none were found.

Excellent result.

 

[don_resqcapt19]

...

Excellent result.

But my point is based on what you read in the trade publications and in manufacturer's information, the plant that I described should have lots of problems and it doesn't.

 

[Besoeker]

But my point is based on what you read in the trade publications and in manufacturer's information, the plant that I described should have lots of problems and it doesn't.

Without a detailed analysis, you simply cannot make that assumption.

 

[iwire]

Without a detailed analysis, you simply cannot make that assumption.

Actually we can, if it is working fine why would we search for a problem in need of a fix?

 

[iwire]

My non scientific statistics shows that the forum moderators has one opinion, while all other posts have the opposite opinion.

What does it mean? Is it due to their experience with discussions with sales people, or maybe the forum selects its moderator according to their approach?

It tells me you cannot count very well, there are many moderators that have not joined in.

How about you explain how you came up with this statement?

Harmonics are the most important issue in today electrical network - it is the most significant reason for fire, failures and losses.

I sure would like to see you back up the above statement of yours as IMHO it is far from accurate. I asked you before for some statistics to back that up and you said you had none.

Then there is this one, lets clear up exactly what you mean.

A word on losses - harmonics can increase the losses to levels of over 30%. If I take 30% of your salary, would you still say it doesn't bother you?

Are you saying reducing harmonics will reduce my utility payment by 30% regardless if the utility penalizes me for it or not?

Considering you brought up reducing my salary by 30% I have to assume you are saying you could reduce a utility bill by 30%.

 

[dbuckley]

Harmonics makes the cables coming into a building smoke as they are a bit hot.

Harmonics make vertical busbars melt.

Harmonics cause terminations to melt and fail.

All seen 1st hand.

I have a second hand story from a reliable source of a dry transformer that failed impressively due to harmonics.

Ok, lots of times harmonics cause no actual problems, but thats not to say they never cause problems. If you fool around with significant non-linear loads at somewhere near the rated capacity of the distribution system, be prepared to see harmonics be an issue.

 

[iwire]

but thats not to say they never cause problems.

I do not think anyone in this thread has said they never cause problems, I know I have not.

My opinion is the issue gets overblown by those with something to sell.

If you fool around with significant non-linear loads at somewhere near the rated capacity of the distribution system, be prepared to see harmonics be an issue.

Bingo!

Design a robust distribution system and you should not need to take 'special' measures to counter harmonic currents.