Electromagnetic compatibility (EMC) - Part 3-6: Limits - Assessment of emission limits for the connection of distorting installations to MV, HV and EHV power systems
This Technical Report, which is informative in its nature, provides guidance on principles
which can be used as the basis for determining the requirements for the connection of
distorting installations to MV, HV and EHV public power systems (LV installations are covered
in other IEC documents). For the purposes of this report, a distorting installation means an
installation (which may be a load or a generator) that produces harmonics and/or
interharmonics. The primary objective is to provide guidance to system operators or owners
on engineering practices, which will facilitate the provision of adequate service quality for all
connected customers. In addressing installations, this document is not intended to replace
equipment standards for emission limits.
The report addresses the allocation of the capacity of the system to absorb disturbances. It
does not address how to mitigate disturbances, nor does it address how the capacity of the
system can be increased.
Since the guidelines outlined in this report are necessarily based on certain simplifying
assumptions, there is no guarantee that this approach will always provide the optimum
solution for all harmonic situations. The recommended approach should be used with
flexibility and judgment as far as engineering is concerned, when applying the given
assessment procedures in full or in part.
The system operator or owner is responsible for specifying requirements for the connection of
distorting installations to the system. The distorting installation is to be understood as the
customer’s complete installation (i.e. including distorting and non-distorting parts).
Problems related to harmonics fall into two basic categories.
• Harmonic currents that are injected into the supply system by converters and harmonic
sources, giving rise to harmonic voltages in the system. Both harmonic currents and
resulting voltages can be considered as conducted phenomena.
• Harmonic currents that induce interference into communication systems. This
phenomenon is more pronounced at higher order harmonic frequencies because of
increased coupling between the circuits and because of the higher sensitivity of the
communication circuits in the audible range.
This report gives guidance for the co-ordination of the harmonic voltages between different
voltage levels in order to meet the compatibility levels at the point of utilisation. The
recommendations in this report do not address harmonic interference phenomena in
communication circuits (i.e. only the first of the above categories is addressed). These
disturbances need to be addressed in terms of international directives concerning the
Protection of Telecommunication Lines against Harmful Effects from Electric Power and
Electrified Railway Lines, International Telecommunication Union, ITU-T Directives [1]2 or in
terms of locally applicable standards such as [2], [3] or [4].
NOTE The boundaries between the various voltage levels may be different for different countries (see
IEV 601-01-28 [32]). This report uses the following terms for system voltages:
– low voltage (LV) refers to Un ≤ 1 kV;
– medium voltage (MV) refers to 1 kV < Un ≤ 35 kV;
– high voltage (HV) refers to 35 kV < Un ≤ 230 kV;
– extra high voltage (EHV) refers to 230 kV < Un.
In the context of this report, the function of the system is more important than its nominal voltage. For example, a
HV system used for distribution may be given a "planning level" which is situated between those of MV and HV
systems.