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Analyzing Harmonics Data on a Power System

Analyzing Harmonics Data on a Power System

Analyzing Harmonics Data on a Power System

(OP)
We are replacing two large induction furnace power supplies. They are fed from a 2500kVA, 15kV-480V transformer, Delta-Wye. The existing units are 800kW, the new ones are 1000kw. They are identical. The power system only feeds these two supplies.

These power supplies work sort of like a VFD, in that they convert to DC then invert the signal so that it operates at 700Hz or so at the induction furnace itself.

I know that this chopping up of the input sine wave creates harmonics. I requested the info from the vendor, which is attached.

My question is...now what to do with the info? My concern has been about the adequacy of this transformer, even though it appears that adding this load will be ok at first glance,  I wonder if the harmonics are increasing the normal current draw and that is something to be concerned with?

And also I know these harmonics reflect back through the power system. Do they need to be filtered?

RE: Analyzing Harmonics Data on a Power System

bdn2004, that file will not come up for me.

RE: Analyzing Harmonics Data on a Power System

ditto

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Analyzing Harmonics Data on a Power System

(OP)
"Explanation: The request timed out before the page could be retrieved. "

I think there may be some technical difficulties with this site....as I get this message above. I also posted a pdf on the paralleling transformer thread a few days ago and I know that worked - but it doesn't now.

Please try again later. If it continues I'll type out some of the info on the report.

RE: Analyzing Harmonics Data on a Power System

Utility will usually ask for some compliance with emission standards.
In US you usually have to show that your installation complies with IEEE 519. If not, you have to install filters to meet the emission levels.

 

RE: Analyzing Harmonics Data on a Power System

(OP)
I just tried the link to the file - it works.  

RE: Analyzing Harmonics Data on a Power System

Works now.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Analyzing Harmonics Data on a Power System

IEEE C57.110 provides calculation examples to evaluate the harmonic heating effects on transformers.

RE: Analyzing Harmonics Data on a Power System

Having a quick look at the file included it looks like you have a current source inverter with a standard 6 pulse rectifier on the input, with a total THDi of 25%.

I'm not sure that I'm reading this correctly as it appears that they're claiming that you have a voltage distortion of 6.9% at the input of the rectifier but at the input to the rectifier transformer they have a voltage distortion of 0.4%. Is this rectifier transformer your on-site 2.5 MVA transformer?

Were these figures taken during commissioning testing or were they an off-site factory test?

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