Harmonic Limitation Standards And Requirements; Harmonic Mitigation; Mg33Bf22; Rev. 2014-04-04 All Rights Reserved - Danfoss VLT AutomationDrive FC 301 Series Design Manual

System Integration
A commonly used term for describing the impedance of a
grid is the short circuit ratio R
between the short circuit apparent power of the supply at
the PCC (S ) and the rated apparent power of the load
sc
(S ).
equ
Sce
Rsce =
Sequ
where
Ssc =
Zsupply
The negative effect of harmonics is two-fold
5 5
•
Harmonic currents contribute to system losses (in
cabling, transformer)
•
Harmonic voltage distortion causes disturbance
to other loads and increase losses in other loads
Non-linear
Current
Contribution to
system losses
Figure 5.6 Negative Effects of Harmonics
5.3.2 Harmonic Limitation Standards and
Requirements
The requirements for harmonic limitation can be
•
application specific requirements
•
standards that must be observed
The application specific requirements are related to a
specific installation where there are technical reasons for
limiting the harmonics.
Example
A 250 kVA transformer with two 110 kW motors connected
is sufficient if one of the motors is connected directly
online and the other is supplied through an adjustable
frequency drive. However, the transformer is undersized if
both motors are supplied by an adjustable frequency drive.
Using additional means of harmonic reduction within the
installation or selecting low harmonic drive variants makes
it possible for both motors to run with adjustable
frequency drives.
60
, defined as the ratio
sce
2
U
and
Sequ = U × Iequ
System
Impedance
Disturbance to
Design Guide
There are various harmonic mitigation standards,
regulations and recommendations. Different standards
apply in different geographical areas and industries. The
following standards are the most common:
•
•
•
•
•
See the AHF 005/010 Design Guide for specific details on
each standard.
In Europe, the maximum THVD is 8% if the plant is
connected via the public grid. If the plant has its own
transformer, the limit is 10% THVD. The VLT
AutomationDrive is designed to withstand 10% THVD.
Voltage

5.3.3 Harmonic Mitigation

In cases where additional harmonic suppression is
other users
required, Danfoss offers a wide range of mitigation
equipment. These are:
•
•
•
•
The choice of the right solution depends on several
factors:
•
•
•
•
Always consider harmonic mitigation if the transformer
load has a non-linear contribution of 40% or more.

5.3.4 Harmonic Calculation

Danfoss offers tools for calculation of harmonics, see
chapter 9.6.5 PC Software.

Rev. 2014-04-04 All rights reserved.

IEC61000-3-2
IEC61000-3-12
IEC61000-3-4
IEEE 519
G5/4
12-pulse drives
AHF filters
Low Harmonic Drives
Active Filters
The grid (background distortion, line power
unbalance, resonance and type of supply
(transformer/generator)
Application (load profile, number of loads and
load size)
Local/national requirements/regulations (IEEE519,
IEC, G5/4, etc.)
Total cost of ownership (initial cost, efficiency,
maintenance, etc.)
®

MG33BF22