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A
lthough the IEEE 519 [1] is not a mandatory standard, its rec-
ommendations are being used as a reference to specify the
harmonic distortion limits allowed by the utility companies
and in the design of industrial power systems.
ANSI/IEEE Standard 519 [1] was published in 1981. It recommend-
ed maximum levels of Total-Harmonic-Voltage-Distortion (THDV) at
the point that the utility connects to different types of users (Point of
Common Coupling (PCC) (see
Figure 1a
)). Different maximum levels
were provided for different types of buildings (see
Figure 1b
).
Figure 1a: PCC.
Figure 1b: THD levels.
IEEE 519 was revised in 1992 to provide recommendations on maxi-
mum allowable levels of harmonic current distortion (see
Figure 2
).
The new standard also defined themaximum recommended contribu-
tion of individual current harmonic orders. The amount of allowable
distortion is based on a ratio of the short circuit current available to
the distribution system (ISC – maximum short circuit current avail-
able at point of common coupling), and the maximum load current
recognised by the distribution system (Il – the maximum load current
of user at the point of common coupling). The larger the user’s load
in relation to the utility transformer supplying that user, the greater
that user’s contribution to the overall harmonic distortion will be.
Hence, stringency of the limits is increased with decreasing Isc/IL ratio.
Figure 2:
• Maximum harmonic current distortion in percent of IL
• Isc - maximum short-circuit current at PCC
• IL - maximum demand load current (fundamental frequency compo-
nent) at PCC
Importantly PCC is the electrical connection point between the util-
ity distribution system and the user's electrical distribution system.
The distortion at the PCC can be evaluated by the current TDD and
the voltage THD, as well as the individual order current harmonics
according to the table.
Often, the limits defined in IEEE 519 [1] have been applied by
engineers to individual equipment instead of the system as a whole,
at the intended PCC. While this approach could well be effective, it
is a misapplication of the standard and can result in unnecessary
use of costly and energy consuming reactors, passive filters, multi-
pulse drives and active filters. It is important to understand the intent
and purpose of this standard and implement it accordingly. Modern
reputable VSD products share a common build typology (VSD design)
This is an extensive subject and as such the points below are intended as an introduction to highlight relevant portions of the IEEE 519 [1]
and to encourage further discussion and analysis.
Glen Ward, ZEST WEG Group
DRIVES, MOTORS + SWITCHGEAR
Points to Consider
to Ensure VSD
Installations Meet IEEE 519
THDV Level
Applications
3%
Airports, Hospitals, Telecommunication Companies
THDV Level
General Applications
5%
Office Buildings, Schools
THDV Level
Dedicated Systems
10%
Factories
Isc / IL
< 11 11
≤
n < 17
17
≤
n < 35
23
≤
n < 35
35
≤
n
TDD (%)
< 20
4
2
1,5
0,6
0,3
5
20 < 50
7
3,5
2,5
1
0,5
8
50 < 100
10
4,5
4
1,5
0,7
12
100 < 1000
12
5,5
5
2
1
15
> 1000
15
7
6
2,5
1,4
20
Electricity+Control
January ‘17
12