High THD impact on XLPE and EPR conductor insulations

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josefbartos

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Please, is there any record/literature that would address high Total Harmonic Distortion (THD) on conductor XLPE and EPR insulation such as reduced life-cycle? I contacted several major USA cable manufacturers; however, they do not have such information available. Also, NFPA 70-2011 National Electrical Code seems to be missing this potentially safety issue.
 
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josefbartos

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Thank you for the very informative posting.
When it comes to the Cross-Linked PolyEthylene, XLPE, conductor insulation and water trees (even small ones), the voltage high harmonic content tends to enable the harmonic current flow through the XLPE insulation and dries the water trees. This leaves the XLPE insulation structurally weakened. The Ethylene Propylene Rubber (EPR) insulation does not have significant water trees; therefore, current with the high harmonic content seems to be less harmful to the EPR insulation.
Please, would there be any test results comparing these two types of conductor insulations available in terms of the voltage or current high harmonic content in conductors with such insulations?
 
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josefbartos said:
Thank you for the very informative posting.
When it comes to the Cross-Linked PolyEthylene, XLPE, conductor insulation and water trees (even small ones), the voltage high harmonic content tends to enable the harmonic current flow through the XLPE insulation and dries the water trees. This leaves the XLPE insulation structurally weakened. The Ethylene Propylene Rubber (EPR) insulation does not have significant water trees; therefore, current with the high harmonic content seems to be less harmful to the EPR insulation.
Please, would there be any test results comparing these two types of conductor insulations available in terms of the voltage or current high harmonic content in conductors with such insulations?
Click to expand...
How is the harmful effect related to the harmonic frequency? Is there a significant effect from just third harmonic components (i.e. 150 or 180 Hz) or is actual insulation damage primarily the result of higher harmonics (such as those from phase controlled switching transients and VFD output circuits)?
Your description above also seems to confuse the effects of voltage harmonics with the effects of current harmonics. I do not see any reason to expect that current harmonics alone would have any effect at all on insulation performance.

The effect of voltage harmonics on the insulation appears to be related to electric field induced (capacitive) currents within the insulation, totally unrelated to harmonic current flow in the wire itself.

(You may be perfectly aware of the distinction, but the wording used may not convey that same information to the casual reader.)
 
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GoldDigger

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josefbartos

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The conductor voltage with harmonic content and conductor current with harmonic content impact the conductor insulation. The conductor insulation has parasitic capacitances and insulation resistances through those harmonic loss current flows. My posting is concerned with the harmonic loss current that flows from the conductor through the conductor parasitic capacitances and insulation resistances, which both can include water trees (white and blue). The attachment in paragraph 2.3.2 on page 12 also adds explanation of harmonic current caused by water trees. This loss current is normally small portion of current that flows through the insulated conductor.
The condensed paragraph 2.3.2:
Water trees introduce higher harmonics into the insulation loss current waveform. The harmonic distortion of the loss current can be correlated with the length of the water trees. Current waveforms for insulation free of water trees or insulation, in which the water trees were completely dried out, show negligible harmonic distortion. Insulation with partially dried water trees maintains significant harmonic distortion of the loss current. Harmonic components arise as a result of the nonlinear voltage-current characteristic of the water treed insulation. Water treeing causes reduced residual ac breakdown strength and high and nonlinearly increasing low-frequency dielectric loss.
However, the intent of my posting is to find out whether or not there are any test results available that would compare life-cycles or losses of frequently used conductors with EPR and XLPE (or TR-XLPE) insulations in terms of applied voltage and current with harmonic contents that exceeds the standard limit of 5% THD and may be as high as 20% THD (for example for LED light loads).
 

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weressl

weressl

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josefbartos said:
The conductor voltage with harmonic content and conductor current with harmonic content impact the conductor insulation. The conductor insulation has parasitic capacitances and insulation resistances through those harmonic loss current flows. My posting is concerned with the harmonic loss current that flows from the conductor through the conductor parasitic capacitances and insulation resistances, which both can include water trees (white and blue). The attachment in paragraph 2.3.2 on page 12 also adds explanation of harmonic current caused by water trees. This loss current is normally small portion of current that flows through the insulated conductor.
The condensed paragraph 2.3.2:
Water trees introduce higher harmonics into the insulation loss current waveform. The harmonic distortion of the loss current can be correlated with the length of the water trees. Current waveforms for insulation free of water trees or insulation, in which the water trees were completely dried out, show negligible harmonic distortion. Insulation with partially dried water trees maintains significant harmonic distortion of the loss current. Harmonic components arise as a result of the nonlinear voltage-current characteristic of the water treed insulation. Water treeing causes reduced residual ac breakdown strength and high and nonlinearly increasing low-frequency dielectric loss.
However, the intent of my posting is to find out whether or not there are any test results available that would compare life-cycles or losses of frequently used conductors with EPR and XLPE (or TR-XLPE) insulations in terms of applied voltage and current with harmonic contents that exceeds the standard limit of 5% THD and may be as high as 20% THD (for example for LED light loads).
Click to expand...

Can you provide accreditation yo your cited dcoument? Author, Publisher, year, etc. Is that document publicly available?
 
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