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#50224 03/27/05 01:17 PM
Joined: Dec 2004
Posts: 1,064
D
Member
I would be intersted in started a thread that dealt with harmonics in a system.

I don't fully understand the in's and outs of why they are harmful, other than the eddy currents flowing in the transformer core causing excessive heat loss.

Is there anything out there that would show me waveforms to look for, how to take measurements and how to decifer readings.

The only way I know how to compensate for it is the use of a K-factor transformer.

I am "green" in this area, so anything would help.

Dnk....

#50225 03/27/05 01:55 PM
Joined: Oct 2000
Posts: 2,749
Member


Joe Tedesco, NEC Consultant
#50226 03/27/05 02:19 PM
Joined: May 2003
Posts: 2,876
E
e57 Offline
Member
Dnkldorf,

Me too!

I know Scott35 has had some things on this in the therory forums, and a quick search in that area brings up some recent questions [Linked Image]


Mark Heller
"Well - I oughta....." -Jackie Gleason
#50227 03/27/05 06:11 PM
Joined: May 2004
Posts: 50
F
Member
I hope they use more than copper to correct harmonics on your side of the pond Guys..we use 90% copper in the UK, and there are still harmonics.

They get introduced to systems by machinery, bad installation design, faulty equipment and a raft of other problems.

Copper handles them better, but it is not a panacea...

#50228 03/27/05 10:00 PM
Joined: Oct 2000
Posts: 2,721
Broom Pusher and
Member
Good idea for a discussion thread, regarding Harmonics/Results of it.

As "E57" mentioned, there have been some threads in the "Electrical Theory and Applications" area, regarding Harmonics. Been discussed in other areas of ECN too.

In a Nutshell, Harmonics are Reflected Currents from certain Equipment connected to an AC source.
They are reflected back into the System at multiples of the Fundamental Frequency - such as if the Fundamental Frequency is 60 Hz, the "Orders" are 120 Hz, 180 Hz, 240 Hz, etc.

In Electrical Circuitry/Power, the ODD order Harmonics (such as the 3rd, 5th, 7th, etc.) are the ones that normally become "Zero Sequenced" - and tend to create issues, such as the issues dealing with "Triple-N" Currents flowing on a Common Grounded Conductor of a 4 Wire Wye System.
These "Triple-N" Currents are additive levels of the 3rd order Harmonic Frequencies (3rd, 9th, etc.) adding up from loads connected between Phase Lines "A"-"N", "B"-"N", and "C"-"N".

The EVEN Order Harmonics in an AC Power System are either Positive Sequenced, or Negative Sequenced, and tend to be of low effect to the System's performance.

These Harmonics can be dealt with in different ways: Filters, Circuitry, "K" Rating of Transformers, Equipment Design, and such.

On the flip side of the coin, there are Harmonics in Audio (Sound), which attribute to the complete percieved "Voice" heard.
(there are others which contribute - such as "Envelope", Attack", "Fundamental(s)", "Delay/Decay", and such).

Harmonics in normal Audible propagnation (typically sound transmitted through the surrunding air), will have the EVEN Orders of the Fundamental(s) causing the most effects - or in the idea of AC Power Systems, they are "Zero-Sequenced"; whereas the ODD Orders will have less effects.
They are opposite of AC Power Systems.

BTW, the Harmonic Distortion of an Acoustical Waveform puts the "Fuzz" sound into an Electric Guitar's distortion sound output.

Just some mini bits of information to ponder!
Hope it's enlightening (sp???).

Feel free to respond and for others to continue this discussion - or best (maybe) to take this to the "Electrical Theory and Applications" area.

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#50229 03/28/05 02:12 PM
Joined: Mar 2005
Posts: 1,803
Member
A long long time ago, far away in another galaxy, I remenber as an apprentice building an amplifier with our Apprentice Master, Mr. James Plaster (ex Sgt. REME) of sacred memory, whom I truly feared. He was a fierce, red faced man, much given to explosions of anger: "Drilled a bleedin' hole through your hand, boy? You won't be doing that again in a hurry!". He departed this life over 45 years ago. We had trouble with harmonics of unknown origin creating noise, which spoiled the performance. The Master said we could filter out the harmonics and we built a device with a shunt coil in series ( ? I think?) with some condensers. If I remember it right, this had to be 'tuned' so as the impedance of the unit was zero at the ripple frequency of the harmonic, and this would 'short out' the high frequency volts. I think we put it across the supply. Mr. P worked out the number of turns with log tables. I only remember the incident because some cretin electrocuted me with with one of the 500v paper condensers wired to my locker as a 'joke'. I literally 'flew' across the shop like Peter Pan. The amp used thermionic-valves of course, none of them useless, new-fangled transistors for Mr.P! The harmonic was measured by the electronics guy at, I'm sure it was, 6 times 50hz = 300hz and there were others far higher than that but faint. Anyway, I moved on to the machine shop soon after, and Mr. P threw one too many wobblies and 'popped his clogs' with a H.A. I'd forgotten it all until the 'harmonic' post appeared. Feel free to shoot me down if I remembered it all wrong.

Alan


Wood work but can't!
#50230 03/28/05 03:23 PM
Joined: Dec 2004
Posts: 1,064
D
Member
Joe, thanks for the site.

Scott, thanks for the info. I did a search for this and didn't find any real answers on the "Theory and Applications" thread so I thought I would post something here to try to get some input. "mostly because I thought harmonics wasn't an application also".

However, I don't think I can move this, maybe Bill can then.

I'll try to start one there, but the guitar thing and the voice thing will confuse farther.

Can we stick to power for the discussion first, as so I can understand that, and then move to the accustical side.


Anyone else want to throw some experience or thoughts down this road?


Dnk..

#50231 03/28/05 09:29 PM
Joined: Oct 2000
Posts: 2,721
Broom Pusher and
Member
Alan;

Love the story!
The description of the Harmonic Filter (Low Pass Filter) is a good starting point for Dnkldorf to grasp the basic Fundamentals of Frequencies / Harmonics.

Dnkldorf;

I'll add more information to the newly started thread at the Theory & Applications area ASAP.
Will keep the data within the basic Electrical scope, then move towards more advanced areas afterwards.

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#50232 03/29/05 01:01 PM
Joined: Mar 2005
Posts: 2
K
Junior Member
A lot of utility companies who are facing harmonics issues generated by customers are taking a new approach.

They install protective relays that measure the harmonics and have penalties in their service contracts. I've heard of some that disconnect a customer who is contirbuting high levels of harmonics, and others that charge them fines whent hey cross certain thresholds.

Devices that can measure this are now quite inexpensive, and it seems a reasonable way to go.

#50233 03/29/05 01:26 PM
Joined: Dec 2004
Posts: 1,064
D
Member
kworkman,

If you can, can you pls post any links to the info you provided here?

I would love to read this about the power companys tariffs reagrding the harmonics.

Is there a cheaper alternative to the Fluke 434 series that would do all the functions of testing and anylizing and trending?

I have researched some, but I am worried about the functionality and versatlity of such equipment.

What do some of you use "test equipment" for this.


Thanks,
Dnk.......


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