Message Board Thread - "Harmonics on Electrical System"

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Harmonics on Electrical System Laland 7/9/2005
Can somebody comment on the effects of harmonics on electrical system? Do harmonics have a great effect on hotspots?
 
Re:Harmonics on Electrical System Bob Berry 7/9/2005
Based on my own experiance harmonics in themselves will not cause hot spots except in extreme cases. They can have an effect on neutral load and can lead to hot neutral conductors, this is more common when a half sized neutral conductor has been used as in some older installations. Generally the biggest problem areas for harmonics is in the Power Factor Correction equipment, due to an effect of the capacitors. This can be eliminated by fitting blocking banks in line with the capacitors. If these have not been fitted there can be an increase in True RMS Load, and this load increase will lead to an increase in hot spot temperature. Although generally the harmonics will in itself not be the cause of the hotspot.

Hope this helps a little.

Check out these links for some more specific information about harmonics
http://www.schneider-electric.ca/www/fr/techpaper/html/actharctrl.htm
http://www.csgnetwork.com/harmonicscalc.html
http://www.essexpower.ca/systemreliability/harmonics.cfm
http://www.ecmweb.com/mag/electric_effects_harmonics_power/
http://www.poweredgetech.com/HarmonicsFrame1Source1.htm
http://www.isdesignet.com/Magazine/Mar'95/ElectMltDwn.html
http://www.ece.umr.edu/links/power/Energy_Course/energy/Pow_quality/ieee_std.htm
 
Re:Harmonics on Electrical System Joe G 10/20/2005
Current harmonics on a system have a direct effect on heating of conductors and components die to the higher frequencies they are present at. They will not create a "hot spot" but a uniform heating throughout not only neutral conductors, but phase conductors as well.

One must understand that there is a distinction to single phase and three phase harmonics in characteristic, frequencies produces, symptoms, and effects.

Single phase harmonics are produced by switch-mode power supplies common in desktop PC's laptops, and electronic lighting ballasts. These devices create triplen harmonics (Multiples of the 3rd order harmonic) that collect and accumulate on common neutrals on a system.

Three phase devices travel back on phase conductors and are produced by such devices as UPS Systems, Variable Frequency Drives, and Inverters. The technology used in these devices will determine which frequencies are produced and what type of effect it can have on components in a system.

Either single or three phase harmonics are certain to be present on most systems today. Most times due to education, engineering and design controls they do not become problematic. However, where the problems due arise is where a facility will introduce newer types of loads onto an older infrastructure that was not intended to handle the higher frequency elements and that is where problematic heating may occur.

Hope this helps.
 
Re:Harmonics on Electrical System jimmyc 10/29/2005
Question?
Would it be possible for harmonics to cause a hot spot on a single neutral connection?
 


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