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The negative effect of harmonics is twofold
Harmonic currents contribute to system losses (in cabling, transformer).
Harmonic voltage distortion causes disturbance to other loads and increase losses in other loads.
N o n- l i n e a r
C u r r e n t
V o l t a g e
S y s t e m
I m p e d a n c e
D i s t u r b a n c e t o
o t h e r u s e r s
C o n t r i b u t i o n t o
s y s t e m l o s s e s
e
3
0
b
b
5
4
1
.1
0
Illustration 83: Negative Effects of Harmonics
10.17.3 IEC Harmonic Standards
In most of Europe, the basis for the objective assessment of the quality of mains power is the Electromagnetic Compatibility fo Devi-
ces Act (EMVG). Compliance with these regulations ensures that all devices and networks connected to electrical distribution sys-
tems fulfill their intended purpose without generating problems.
Table 98: EN Design Standards for Mains Power Quality
Standard
Definition
EN 61000-2-2, EN 61000-2-4, EN 50160 Define the mains voltage limits required for public and industrial power grids.
EN 61000-3-2, 61000-3-12
Regulate mains interference generated by connected devices in lower current products.
EN 61800-3
Monitors electronic equipment for use in power installations.
There are 2 European standards that address harmonics in the frequency range from 0 Hz to 9 kHz:
EN 61000-2-2 Compatibility Levels for Low-Frequency Conducted Disturbances and Signaling in Public Low-Voltage Power Sup-
ply Systems.
EN 61000-2-4 Compatibility Levels for Low-Frequency Conducted Disturbances and Signaling in Industrial Plants.
The EN 61000-2-2 standard states the requirements for compatibility levels for PCC (point of common coupling) of low voltage AC
systems on a public supply network. Limits are specified only for harmonic voltage and total harmonic distortion of the voltage. EN
61000-2-2 does not define limits for harmonic currents. In situations where the total harmonic distortion THDv=8%, PCC limits are
identical to those limits specified in the EN 61000-2-4 Class 2.
The EN 61000-2-4 standard states the requirements for compatibility levels in industrial and private networks. The standard further
defines the following 3 classes of electromagnetic environments:
Class 1 relates to compatibility levels that are less than the public supply network, which affects equipment sensitive to distur-
bances (lab equipment, some automation equipment, and certain protection devices).
Class 2 relates to compatibility levels that are equal to the public supply network. The class applies to PCCs on the public supply
network and to IPCs (internal points of coupling) on industrial or other private supply networks. Any equipment designed for
operation on a public supply network allowed in this class.
Class 3 relates to compatibility levels greater than the public supply network. This class applies only to IPCs in industrial environ-
ments. Use this class where the following equipment is found:
Large drives.
Welding machines.
Large motors starting frequently.
Loads that change quickly.
Typically, a class cannot be defined ahead of time without considering the intended equipment and processes to be used in the
environment.
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