• Technology

Power Quality / IEC 61000 

In the IEC 61000-series block, there is a mix of standards with varying requirements. In Europe, the predominant standards are IEC 61000-2-2 which covers low frequency disturbances in public networks and IEC 61000-2-4 that covers low frequency disturbances in industrial and non-public networks. Note the term “low-frequency”; in this context, low frequency is up to 9 kHz, or the equivalent of the 180th harmonic in a 50 Hz grid. 

IEC61000

IEC 61000-2-2 requires a maximum voltage distortion of 8 %, and IEC 61000-2-4 requires a maximum voltage distortion of 5 % (in class 1, protected supplies), 8 % (in class 2, industrial networks) and 10 % (in class 3, dedicated or heavy industry networks). The levels below are compatibility levels meaning that they cannot directly or easily be translated to acceptable emission levels. In other words, it is difficult to apply this standard to an installation or a piece of equipment in order to make sure if the machine or equipment will comply with regulation; rather, the limits will tell if an installation as a whole is compliant or not.

IEC 61000-2-2:2002

Odd harmonics 
non-multiple of 3
Odd harmonics
multiple of 3
Even harmonics
Harmonic
Order
h
Harmonic
Voltage
%
Harmonic
Order
h
Harmonic
Voltage
%
Harmonic
Order
h
Harmonic
Voltage
%
5 6 3 5 2 2
6 5 9 1.5 4 1
11 3.5 15 0.4 6 0.5
13 3 21 0.3 8 0.5
17 ≤ h ≤ 37 2.27 x (17/h) – 0.27  21 < h ≤ 39 0.2 10 ≤ h ≤ 40 0.25 x (10/h) + 0.25 

IEC 61000-2-4:2002

Harmonic Order
h
Class 1 
Harmonic Voltage 
%
Class 2 
Harmonic Voltage 
Class 3 
Harmonic Voltage 
5 3 6 8
7 3 5 7
11 3 3.5 5
13 3 3 4.5
17 2 2 4
17 < h ≤ 49 2.27 x (17/h) – 0.27 2.27 x (17/h) – 0.27 4.5 x (17/h) – 0.5 
Harmonic Order
h
Class 1 
Harmonic Voltage 
%
Class 2 
Harmonic Voltage 
Class 3 
Harmonic Voltage 
3 3 5 6
9 1.5 1.5 2.5
15 0.3 0.4 2
21 0.2 0.3 1.75 
21 < h ≤ 45  0.2 0.2 1
Harmonic Order
h
Class 1 
Harmonic Voltage 
%
Class 2 
Harmonic Voltage 
Class 3 
Harmonic Voltage 
2 2 2 3
4 1 1 1.5
6 0.5 0.5 1
8 0.5 0.5 1
10 0.5 0.5 1
10 < h ≤ 50  0.25 x (10/h) – 0.25 0.25 x (10/h) – 0.25 1

Additional standards cover regulation of individual pieces of equipment, such as IEC 61000-3-2 or IEC 61000-3-12. The latter cover limit for harmonic currents produced by equipment connected to public low voltage systems with more than 16 A but less or equal than 75 A per phase.

Table 3 – Current emission limits for balanced three-phase equipment (IEC 61000-3-12 (2011), pg. 15)

Minimum Rsce Admissible individual harmonic current Ih/Iref a 
(%) 
Admissible harmonic parameters (%) 
I5 I7 I11 I13 THC/Iref PWHC/Iref
33 10.7 7.2  3.1 2 13 22
66 14 9 5 3 16 25
120 19 12 7 4 22 28
250 31 20 12 7 37 38
350  40 25 15 10 48 46
The relative values of even harmonics up to order 12 shall not exceed 16/h %. Even harmonics above order 12 are taken into account into THC and PWHC in the same way as odd order harmonics. Linear interpolation between successive Rsce values is permitted.
a Iref = reference current; Ih = harmonic current component

As can be seen, like in IEEE 519, an increased Rsce (which is equivalent to Isc/IL) allows for higher current harmonics. (As a reminder, for a discussion on how current harmonics are converted into voltage harmonics, see Appendix C.) Again, this is reasonable and understandable in a system standard, however very confusing in a product standard. For a user of the product, it might be impossible to know the relevant limits – since interpolation is allowed, the exact limits must be calculated! From a testing standpoint, the requirements on the same product will vary wildly depending on where it is installed. To complicate things further, there are several tables outlining the harmonic requirements, and there is even a flowchart to determine which table to use. Below is table 5 from IEC 61000-3-12: 

Table 5 – Current emission limits for balanced three-phase equipment under specified conditions (d, e, f) (IEC 61000-3-12 (2011), pg. 16)

Minimum
Rsce
Admissible individual harmonic current Ih/Iref a 
(%) 
Admissible harmonic parameters (%)
I5 I7 I11 I13 I17 I19 I23 I25 I29 I31 I35 I37 THC / Iref  PWHC / Iref
33  10.7 7.2 3.1 2 2 1.5 1.5 1.5 1 1 1 1 13 22
≥250 25 17.3 12.1 10.7 8.4 7.8 6.8 6.5 5.4 5.2 4.9 4.7 35 70
For Rsce equal to 33, the relative values of even harmonics up to order 12 shall not exceed 16/h %. The relative values of all harmonics from I14 to I40 not listed above shall not exceed 1% of Iref. For Rsce ≥250, the relative values of even harmonics up to order 12 shall not exceed 16/h %. The relative values of all harmonics from I14 to I40 not listed above shall not exceed 3% of Iref. Linear interpolation between successive Rsce values is permitted.
a Iref = reference current; Ih = harmonic current component

As can be seen, the table only specifies minimum and maximum levels, and the reader must interpolate to find the relevant level. In defense of the standard, it is stated that the Rsce = 33 level must be selected for full product compliance. However, since voltage limits are not defined in the same standard, there is no guarantee that the emission levels are compatible with the required harmonic distortion levels in other IEC 61000 standards!

It can be discussed whether the various IEC standards always fill the gap between compatibility levels and emission levels; this is beyond the scope of this text.

IMPORTANT INFORMATION! By sharing personal information on this website you also agree to the use of this information by Comsys AB in accordance with the General Data Protection Regulation (GDPR). If you have any questions regarding the General Data Protection Regulation you can contact Comsys AB at or read more at https://www.datainspektionen.se/dataskyddsreformen (in Swedish) or https://www.eugdpr.org (in English) By continuing you agree to the use of personal information in accordance with GDPR.

NOTE! This site uses cookies and similar technologies. Unless you change browser settings, you agree to it.

© Comsys AB 2020 All rights reserved
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.