Harmonics Content on the Distribution System
Harmonics Content on the Distribution System
(OP)
I came across a situation during a power quality investigation on a 13.8KV, 4-wire multi-grounded, distribution feeder.
The data showed large 3rd and 5th voltage harmonic content. The current harmonics were low on the 3rd and 5th, but high on 9th and 11th. This trend was uniform across the feeder.
I am perplexed as to why the high content voltage and current harmonics components do not correlate. I have spoken with someone that, while rare he said, has seen this a couple of times in his long career, but has never found an explanation.
Has anyone seen this in the past? What might cause this?
Thank you!
The data showed large 3rd and 5th voltage harmonic content. The current harmonics were low on the 3rd and 5th, but high on 9th and 11th. This trend was uniform across the feeder.
I am perplexed as to why the high content voltage and current harmonics components do not correlate. I have spoken with someone that, while rare he said, has seen this a couple of times in his long career, but has never found an explanation.
Has anyone seen this in the past? What might cause this?
Thank you!






RE: Harmonics Content on the Distribution System
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Harmonics Content on the Distribution System
The current harmonic will be for your feeder loads.
What loads do you have that will generate 9th and 11th harmonics?
There are probably loads on the distribution system that are generating a lot of 3rd and 5th harmonics. You will not see these currents, but you will see the effect that they cause on the system voltage.
Your loads may be generating 9th and 11th, and you will see the currents but on a stiff system your harmonic currents may not be able to influence the system voltage very much.
Bill
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"Why not the best?"
Jimmy Carter
RE: Harmonics Content on the Distribution System
Is perhaps the voltage distortion being caused by adjacent feeders off the same bus, and the current harmonic content on the feeder of interest, while significant on this feeder, does not have a significant impact on the substation distribution transformer low-side bus voltage harmonic content as much as other sources? Is it possible resonance playing a role?
Pat
RE: Harmonics Content on the Distribution System
The greatest voltage drop will be in the feeders and the supply transformer. If the harmonic currents are great enough voltage drops will be created also on the distribution lines along with harmonic contribution from other users on that distribution line.
All the loads on that distribution line contribute to the harmonic voltages. Ampmeters on a feeder will see harmonic currents on that feeder only.
The source of the 9th and 11th harmonic voltages may be any of your feeders, any other loads on the distribution circuit or loads on other distribution circuits on the same power transformer at the sub station.
What are your loads?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Harmonics Content on the Distribution System
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Harmonics Content on the Distribution System
RE: Harmonics Content on the Distribution System
Pat
RE: Harmonics Content on the Distribution System
Can you measure the total substation current harmonics?