3. Reduction of the harmonic losses in low-voltage networks

In order to reduce the third-order harmonic currents by properly combining lamps that have an important phase difference in their corresponding harmonic currents (rather than combining lamps in a random way), the phase angle (φ3) of the third-order harmonic currents was first measured (with respect to the fundamental harmonic voltage angle of the phase 1) for the CFL and LED lamps. The results are given in Table 3.

Data in Table 3 correspond to time-averaged values over an interval of 5 minutes with a sampling rate of 1 S/s. The data were taken applying nominal voltage to the lamps once they acquired their stable working temperature. A power quality analyzer (Fluke 435-II) was used in the measurements. The experimental uncertainty (mainly due to statistical fluctuations) was within 5. In order to match the measuring range of the instrument used to the relatively small currents of the lamp combinations, the currents were measured by using low-inductance (around 0.1 mH) coils. It was verified during the measurements that the inductance introduced in the circuit by the coils does not appreciably affect the results. The uncertainty ( 2%) in the current measurement due to the position sensitivity of the used flexible current probe was accounted for. The information provided by the instrument was processed through the PowerLog 4.3.1 software.

currents for several selected combination types LED-LED and LED-CFL of the lamps used in this work. The corresponding experimental uncertainty (mainly due to statistical fluctuations)

Figure 8. Stability of the phase angle of the third-order harmonic current for several lamps used [35].

To find the level of attenuation of the third-order harmonic currents as a consequence of the combinations of lamps, it is useful to define the diversity factor for the harmonic current, as the ratio between the vector sum (as measured) and the arithmetical sum (as calculated) of the

DF<sup>3</sup> � j j vector sum of current harmonic

Note that a value of DF<sup>3</sup> ≈ 1 indicates an inadequate combination of lamps, which generates a minimum attenuation of the third-order harmonic currents, whereas DF<sup>3</sup> < < 1 implies an optimum combination, with a maximum attenuation of this harmonic current. Figure 9 shows the dependence of measured DF<sup>3</sup> for selected lamp combinations on the difference between the corresponding phase angles of the third-order harmonic currents. The solid curves represent the diversity factor calculated for limit values of the ratio between the amplitudes of the thirdorder harmonic current of each lamp of the combination (values calculated for a ratio = 1 are indicated with a blue line while for a ratio = 7 with a red line). Note that these values are close to the minimum and maximum ratios obtained in the different combinations proposed, as it

It is seen in Figure 9 that a number of combinations of LED and CFL lamps lead to a considerably decrease in the content of the third-order harmonic current. As expected, the maximum attenuation of the third harmonic amplitude is achieved with harmonic ratios close to 1 and for harmonic phase angle differences close to 180�. These results are different from those reported by other studies [33, 34] where lower-order harmonics did not exhibit a very large reduction in amplitude. However, it should be noted that in [33, 34] random combina-

Note that the results presented in Figure 9 were obtained combining two lamps; however, the same results could be obtained between two arbitrary sets of lamps, provided that each set is formed by the same number of elements. Currently, CFLs are being replaced by LEDs gradually, and in several lighting installations, the two technologies coexist. From the point of view of the reduction of the third harmonic, the combinations of lamps of different technologies are

arithmetic sum of current harmonic : (20)

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69

was within �7%.

third-order harmonic currents:

was indicated in Table 4.

tions of lamps were used.

During the measurements, the phase angles of the third-order harmonic currents were remarkably stable as shown in Figure 8. The corresponding experimental uncertainty (mainly due to statistical fluctuations) was within 5.

In order to achieve a considerable attenuation effect of the third-order harmonic currents for a given combination of lamps, they should not only fulfil with the condition that its third-order harmonic be strongly out of phase (as is the case of LED Alic 3 W and LED Philips 8 W), but also the amplitudes of each harmonic current should be similar, i.e. the ratio between the amplitudes of the third-order harmonic current of each lamp should be approximately united. Table 4 shows the results of the ratio between the amplitudes of the third-order harmonic


Table 3. Angle of the third-order harmonic current of the lamps used [35].

The Impact of the Use of Large Non-Linear Lighting Loads in Low-Voltage Networks http://dx.doi.org/10.5772/intechopen.76752 69

Figure 8. Stability of the phase angle of the third-order harmonic current for several lamps used [35].

3. Reduction of the harmonic losses in low-voltage networks

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

CFL and LED lamps. The results are given in Table 3.

PowerLog 4.3.1 software.

statistical fluctuations) was within 5.

LED Sica 13 W 129

Table 3. Angle of the third-order harmonic current of the lamps used [35].

In order to reduce the third-order harmonic currents by properly combining lamps that have an important phase difference in their corresponding harmonic currents (rather than combining lamps in a random way), the phase angle (φ3) of the third-order harmonic currents was first measured (with respect to the fundamental harmonic voltage angle of the phase 1) for the

Data in Table 3 correspond to time-averaged values over an interval of 5 minutes with a sampling rate of 1 S/s. The data were taken applying nominal voltage to the lamps once they acquired their stable working temperature. A power quality analyzer (Fluke 435-II) was used in the measurements. The experimental uncertainty (mainly due to statistical fluctuations) was within 5. In order to match the measuring range of the instrument used to the relatively small currents of the lamp combinations, the currents were measured by using low-inductance (around 0.1 mH) coils. It was verified during the measurements that the inductance introduced in the circuit by the coils does not appreciably affect the results. The uncertainty ( 2%) in the current measurement due to the position sensitivity of the used flexible current probe was accounted for. The information provided by the instrument was processed through the

During the measurements, the phase angles of the third-order harmonic currents were remarkably stable as shown in Figure 8. The corresponding experimental uncertainty (mainly due to

In order to achieve a considerable attenuation effect of the third-order harmonic currents for a given combination of lamps, they should not only fulfil with the condition that its third-order harmonic be strongly out of phase (as is the case of LED Alic 3 W and LED Philips 8 W), but also the amplitudes of each harmonic current should be similar, i.e. the ratio between the amplitudes of the third-order harmonic current of each lamp should be approximately united. Table 4 shows the results of the ratio between the amplitudes of the third-order harmonic

Lamp type φ<sup>3</sup> (degrees) Lamp type φ<sup>3</sup> (degrees)

LED Alic 3 W 95 LED Philips 14 W 33 LED Sylvania 5.5 W 112 LED TBC in 14 W 126 LED Osram 8 W 126 LED Sica 15 W 130 LED Philips 8 W 77 LED Philips 18 W 125 LED Lumenac 8 W 9 CFL Sica 11 W 114 LED Sica 9 W 153 CFL Osram 13 W 111 LED Philips 9 W 9 CFL Philips 15 W 111 LED GE 10 W 49 CFL Sylvania 20 W 119 LED Philips 13 W 2 CFL Philips 23 W 108 currents for several selected combination types LED-LED and LED-CFL of the lamps used in this work. The corresponding experimental uncertainty (mainly due to statistical fluctuations) was within �7%.

To find the level of attenuation of the third-order harmonic currents as a consequence of the combinations of lamps, it is useful to define the diversity factor for the harmonic current, as the ratio between the vector sum (as measured) and the arithmetical sum (as calculated) of the third-order harmonic currents:

$$DF\_3 \equiv \frac{|\text{vector sum of current harmonic}|}{\text{arithmetic sum of current harmonic}}.\tag{20}$$

Note that a value of DF<sup>3</sup> ≈ 1 indicates an inadequate combination of lamps, which generates a minimum attenuation of the third-order harmonic currents, whereas DF<sup>3</sup> < < 1 implies an optimum combination, with a maximum attenuation of this harmonic current. Figure 9 shows the dependence of measured DF<sup>3</sup> for selected lamp combinations on the difference between the corresponding phase angles of the third-order harmonic currents. The solid curves represent the diversity factor calculated for limit values of the ratio between the amplitudes of the thirdorder harmonic current of each lamp of the combination (values calculated for a ratio = 1 are indicated with a blue line while for a ratio = 7 with a red line). Note that these values are close to the minimum and maximum ratios obtained in the different combinations proposed, as it was indicated in Table 4.

It is seen in Figure 9 that a number of combinations of LED and CFL lamps lead to a considerably decrease in the content of the third-order harmonic current. As expected, the maximum attenuation of the third harmonic amplitude is achieved with harmonic ratios close to 1 and for harmonic phase angle differences close to 180�. These results are different from those reported by other studies [33, 34] where lower-order harmonics did not exhibit a very large reduction in amplitude. However, it should be noted that in [33, 34] random combinations of lamps were used.

Note that the results presented in Figure 9 were obtained combining two lamps; however, the same results could be obtained between two arbitrary sets of lamps, provided that each set is formed by the same number of elements. Currently, CFLs are being replaced by LEDs gradually, and in several lighting installations, the two technologies coexist. From the point of view of the reduction of the third harmonic, the combinations of lamps of different technologies are usually convenient. For the lamps evaluated, the change of technology (CFL to LED) not only improves the level of illumination and reduces the content of third harmonic but also decreases the active power demanded by the installation, reducing also the environmental impact.

one phase and in the neutral conductor of a four-core cable, feeding balanced single-phase loads formed by selected LED-LED combination is shown in Figures 10(a) and (b), respectively. The corresponding spectrums for the individual lamps are also shown. Harmonic currents up to the order h = 19 were measured. In addition, the rms value of the total current

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It is seen in Figure 10 that the selected LED combination leads to a significant decrease in the third-order harmonic content of the line current. Notice also that the RMS value of the total current of the combination is considerable lower than the corresponding value of the individual lamp having the higher harmonic content of the combination (LED Sica 9 W), being similar

As it can be seen in Figure 10, the RMS value of the total current of the combination is strongly reduced with respect to that of the LED Sica 9 W, mostly due to a decrease in the content of the third-order harmonic current, although some reduction is also observed for the high-order harmonics. It is important to note that the current of the LED Sica 9 W has a strong component of the third-order harmonic (exceeding the emission limit imposed by IEC as quoted in Section 1) and also of high-order harmonics (h = 9 and 15). As the overall harmonic power losses in the neutral conductor depend on the RMS value of the total current, a marked reduction in the harmonic losses with respect to that of the LED Sica 9 W (and even with respect to the LED

Notice also the negligible small value of the first-order harmonic current in the neutral conductor due to the balanced loading of the cable. The small residuals observed are due in part to small asymmetries attributable to the constructive differences between the lamps tested.

The cable harmonic power losses can be approximately calculated by Eq. (18). To quantify the reduction in the harmonic power losses due to the lamp combination, it is useful to compare

Figure 10. Harmonic current content in one phase (a) and in the neutral conductor (b) of a four-core cable for a selected

in both conductors is presented in Figures 10(a) and (b).

Lumenac 8 W) is expected for the tested lamp combination.

to that of the LED Lumenac 8 W.

LED-LED combination.

In order to better show the contribution of the proposed solution, the measured spectrum of the harmonic currents (expressed in per unit of the fundamental harmonic current), both in


Table 4. Tested combinations of lamps [35].

Figure 9. Attenuation of the third harmonic by combination of lamps [35].

one phase and in the neutral conductor of a four-core cable, feeding balanced single-phase loads formed by selected LED-LED combination is shown in Figures 10(a) and (b), respectively. The corresponding spectrums for the individual lamps are also shown. Harmonic currents up to the order h = 19 were measured. In addition, the rms value of the total current in both conductors is presented in Figures 10(a) and (b).

usually convenient. For the lamps evaluated, the change of technology (CFL to LED) not only improves the level of illumination and reduces the content of third harmonic but also decreases the active power demanded by the installation, reducing also the environmental impact.

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

In order to better show the contribution of the proposed solution, the measured spectrum of the harmonic currents (expressed in per unit of the fundamental harmonic current), both in

Lamp combination Ratio between the amplitudes (rms) of the third-order

CFL Philips 23 W-LED Philips 18 W 1.1 CFL Philips 15 W-LED Philips 13 W 1.8 LED Lumenac 8 W-LED Sica 9 W 1.9 LED Philips 13 W-LED Sica 13 W 1.9 LED Osram 8 W-LED Lumenac 8 W 2.3 CFL Sica 11 W-LED Philips 9 W 2.6 LED Sica 9 W-LED Philips 9 W 2.8 CFL Sica 11 W-LED Osram 8 W 4.6 CFL Philips 15 W-LED Philips 14 W 4.7 LED Philips 14 W-LED TBC in 14 W 114 W 4.7 CFL Sica 11 W-LED GE 10 W 6.7 CFL Sylvania 20 W-LED Philips 14 W 6.8

Table 4. Tested combinations of lamps [35].

Figure 9. Attenuation of the third harmonic by combination of lamps [35].

harmonic current of each lamp of the combination

It is seen in Figure 10 that the selected LED combination leads to a significant decrease in the third-order harmonic content of the line current. Notice also that the RMS value of the total current of the combination is considerable lower than the corresponding value of the individual lamp having the higher harmonic content of the combination (LED Sica 9 W), being similar to that of the LED Lumenac 8 W.

As it can be seen in Figure 10, the RMS value of the total current of the combination is strongly reduced with respect to that of the LED Sica 9 W, mostly due to a decrease in the content of the third-order harmonic current, although some reduction is also observed for the high-order harmonics. It is important to note that the current of the LED Sica 9 W has a strong component of the third-order harmonic (exceeding the emission limit imposed by IEC as quoted in Section 1) and also of high-order harmonics (h = 9 and 15). As the overall harmonic power losses in the neutral conductor depend on the RMS value of the total current, a marked reduction in the harmonic losses with respect to that of the LED Sica 9 W (and even with respect to the LED Lumenac 8 W) is expected for the tested lamp combination.

Notice also the negligible small value of the first-order harmonic current in the neutral conductor due to the balanced loading of the cable. The small residuals observed are due in part to small asymmetries attributable to the constructive differences between the lamps tested.

The cable harmonic power losses can be approximately calculated by Eq. (18). To quantify the reduction in the harmonic power losses due to the lamp combination, it is useful to compare

Figure 10. Harmonic current content in one phase (a) and in the neutral conductor (b) of a four-core cable for a selected LED-LED combination.

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

$$\xi \equiv \frac{P\_{\rm loss}}{\Im I\_{\rm RMS}^2(1)\,\mathrm{R}\_{\rm ac}(1) + \,\,\,I\_{\rm RMS}\,\mathrm{N}^2(1)\,\mathrm{R}\_{\rm ac}(1)},\tag{21}$$

2. An incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severely harmonic

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In order to reduce the third-order harmonic currents in the neutral conductor, an experimental investigation of diversity factors for LED in combination with CFL and LED lamps was also performed. An experimental investigation of diversity factors for LED (light emitting diode) in combination with CFL (compact fluorescent lamps) and LED lamps with nominal powers <25 W was presented. In contrast to other works, attention was paid to the reduction of low-order harmonics, especially the third one, which is mainly responsible for the strong increase in power losses in the neutral conductor of the low-voltage installations. The results showed that a number of selected combinations of LED and CFL lamps lead to a considerable decrease in the content of the third-order harmonic current. These results are different from those reported by other studies where lower-order harmonics did not exhibit a very large reduction in amplitude. However, it should be noted that in those studies random combinations of lamps were used. The convenience of having LED lamps designed to operate as two-phase loads is suggested for certain applications of significant power

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

1 Electrical Discharge Group, Department of Electromechanical Engineering, Venado Tuerto Regional Faculty, National Technological University, Venado Tuerto (Santa Fe), Argentina

2 Electrical Discharge Group, Department of Electromechanical Engineering, Venado Tuerto Regional Faculty, National Technological University, CONICET, Venado Tuerto (Santa Fe),

3 Master in Energy for Sustainable Development, Faculty of Exact Science, Eng. and

4 Faculty of Exact Science, Eng. and Surveying, Rosario National University, Rosario

Surveying, Rosario National University, Rosario (Santa Fe), Argentina

, Miguel A. Lara<sup>3</sup> and Diego Milardovich<sup>4</sup>

published in Advanced Electromagnetic Journal to write part of the presented chapter.

\*, Leandro Prevosto2

\*Address all correspondence to: njmilardovich@gmail.com

emission limits should be defined for LED lamps.

demand.

Acknowledgements

Author details

Argentina

Natalio Milardovich<sup>1</sup>

(Santa Fe), Argentina

(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) are connected between lines instead as single-phase loads.

### 4. Conclusions

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 examined. This study has shown that:

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 harmonics in the distorted current.

2. An incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severely harmonic emission limits should be defined for LED lamps.

In order to reduce the third-order harmonic currents in the neutral conductor, an experimental investigation of diversity factors for LED in combination with CFL and LED lamps was also performed. An experimental investigation of diversity factors for LED (light emitting diode) in combination with CFL (compact fluorescent lamps) and LED lamps with nominal powers <25 W was presented. In contrast to other works, attention was paid to the reduction of low-order harmonics, especially the third one, which is mainly responsible for the strong increase in power losses in the neutral conductor of the low-voltage installations. The results showed that a number of selected combinations of LED and CFL lamps lead to a considerable decrease in the content of the third-order harmonic current. These results are different from those reported by other studies where lower-order harmonics did not exhibit a very large reduction in amplitude. However, it should be noted that in those studies random combinations of lamps were used. The convenience of having LED lamps designed to operate as two-phase loads is suggested for certain applications of significant power demand.
