Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads.
Date
2014
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Abstract
A numerical investigation on the harmonic disturbances in
low-voltage cables feeding large LED loads is reported. A
frequency domain analysis on several commercially available LEDs was performed to investigate the signature
of the harmonic current injected into the power system.
Four-core cables and four single-core cable arrangements
(three phases and neutral) of small, medium, and large
conductor cross sections, with the neutral conductor cross
section approximately equal to the half of the phase
conductors, were examined. The cables were modelled by
using electromagnetic finite-element analysis software. High
harmonic power losses (up to 2.5 times the value
corresponding to an undistorted current of the same rms
value of the first harmonic of the LED current) were found.
A generalized ampacity model was employed for re-rating
the cables. It was found that the cross section of the neutral
conductor plays an important role in the derating of the
cable ampacity due to the presence of a high-level of triplen
harmonics in the distorted current. The ampacity of the
cables should be derated by about 40 %, almost independent
of the conductor cross sections. The calculation have shown
that an incoming widespread use of LED lamps in lighting
could create significant additional harmonic losses in the
supplying low-voltage lines, and thus more severe harmonic
emission limits should be defined for LED lamps.
Description
Keywords
Low-voltage., Harmonic losses., LED lamps.
Citation
ADVANCED ELECTROMAGNETICS.
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