Harmonics standards

Harmonic emissions are subject to various standards and regulations:

• Compatibility standards for distribution networks
• Emissions standards applying to the equipment causing harmonics
• Recommendations issued by Utilities and applicable to installations

In view of rapidly attenuating the effects of harmonics, a triple system of standards and regulations is currently in force based on the documents listed below.

Standards governing compatibility between distribution networks and products

These standards determine the necessary compatibility between distribution networks and products:

• The harmonics caused by a device must not disturb the distribution network beyond certain limits
• Each device must be capable of operating normally in the presence of disturbances up to specific levels
• Standard IEC 61000-2-2 is applicable for public low-voltage power supply systems
• Standard IEC 61000-2-4 is applicable for LV and MV industrial installations

Standards governing the quality of distribution networks

• Standard EN 50160 stipulates the characteristics of electricity supplied by public distribution networks
• Standard IEEE 519 presents a joint approach between Utilities and customers to limit the impact of non-linear loads. What is more, Utilities encourage preventive action in view of reducing the deterioration of power quality, temperature rise and the reduction of power factor. They will be increasingly inclined to charge customers for major sources of harmonics

Standards governing equipment

• Standard IEC 61000-3-2 for low-voltage equipment with rated current under 16 A
• Standard IEC 61000-3-12 for low-voltage equipment with rated current higher than 16 A and lower than 75 A

Maximum permissible harmonic levels

International studies have collected data resulting in an estimation of typical harmonic contents often encountered in electrical distribution networks. Figure M23 presents the levels that, in the opinion of many Utilities, should not be exceeded.

		LV	MV	HV
Odd harmonics non-multiple of 3	5	6	5	2
	7	5	4	2
	11	3.5	3	1.5
	13	3	2.5	1.5
	17 ≤ h ≤ 49	[math]\displaystyle{ 2.27\frac{17}{h}-0.27 }[/math]	[math]\displaystyle{ 1.9\frac{17}{h}-0.2 }[/math]	[math]\displaystyle{ 1.2\frac{17}{h} }[/math]
Odd harmonics multiple of 3	3	5	4	2
	9	1.5	1.2	1
	15	0.4	0.3	0.3
	21	0.3	0.2	0.2
	21 ≤ h ≤ 45	0.2	0.2	0.2
Even harmonics	2	2	1.8	1.4
	4	1	1	0.8
	6	0.5	0.5	0.4
	8	0.5	0.5	0.4
	10 ≤ h ≤ 50	[math]\displaystyle{ 0.25\frac{10}{h}+0.25 }[/math]	[math]\displaystyle{ 0.25\frac{10}{h}+0.22 }[/math]	[math]\displaystyle{ 0.19\frac{10}{h}+0.16 }[/math]
THDU		8	6.5	3

Fig. M23 – Maximum admissible harmonic voltages and distortion (%)