Acknowledgements

the above calculated cable losses with the losses produced in an identical cable but carrying an undistorted electric current of the same RMS value as the first harmonic current of the

ð Þ1 Racð Þþ 1 IRMS N

(the first-order harmonic current in the neutral conductor is due to small asymmetries in the single-phase loads) was calculated on the basis of the measured data by neglecting the influence of the harmonic frequency on the resistance of the conductors (i.e. the conductor radius is small compared to the characteristic skin penetration length, and the distances of the nearby conductors are large compared to the conductor radius [29]). For a neutral conductor having a cross section equal to half of the phase conductor section [38], it results in a value of 9.6, 3.3 and 2.8 for the individual lamps LED Sica 9 W and LED Lumenac 8 W and for the combination, respectively, thus showing that the tested lamp combination leads to a significant decrease in the power harmonic losses. A similar result can be obtained for other lamp combination provided that the diversity factor for the third-order harmonic current of the arrangement is small enough.

Note that in lighting loads of substantial power demand such as those considered in this work, it would be convenient from the point of view of the reduction of the power losses to connect the LED lamps between lines (rather than between a line and the neutral conductor). In such case, the third-order harmonic currents (and their multiples) cannot flow through the network since the return path through the neutral conductor does not exist. This suggests the convenience of having LED lamps including ac/dc converters designed to operate as two-phase loads. As quoted before, a large number of the existing low-voltage installations present a neutral conductor with a reduced section (about half of the phase conductor) [38]. These installations when feeding LED loads could present more than twice the losses corresponding to a current without distortion of the same rms as the value of the first harmonic current of the lamps [13]; thus, a marked reduction (over ~ 50%) in the overall harmonic power losses can be expected if the LED lamps (having ac/dc converters designed to operate as two-phase loads)

Calculation of harmonic disturbances in low-voltage network installations having the neutral cross section approximately equal to half of the phase conductors when used for feeding large LED lighting loads was reported. The cables were modeled by using electromagnetic finite element analysis software. Four-core cables and four single-core cable arrangements (three phases and neutral conductor) of small, medium and large conductor cross sections were

1. The cross section of the neutral conductor plays an important role in the harmonic losses and thus in the derating of the cable ampacity, due to the presence of a high level of triplen

2

ð Þ<sup>1</sup> Rac Nð Þ<sup>1</sup> , (21)

distorted current. To do this, the cable loss ratio defined as

are connected between lines instead as single-phase loads.

4. Conclusions

examined. This study has shown that:

harmonics in the distorted current.

<sup>ξ</sup> � Ploss 3IRMS 2

72 Light-Emitting Diode - An Outlook On the Empirical Features and Its Recent Technological Advancements

N. M. and L. P. acknowledge financial support by the National Technological University (PID 3568). L. P. and M. A. L. are members of the CONICET. We have reused our own original work published in Advanced Electromagnetic Journal to write part of the presented chapter.
