Dirty power Are you in the dark about Harmonics? - Schneider Electric

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Schneider Electric
The Newsletter of
Schneider Electric
New Zealand
March 2012
Dirty power
Are you in the dark
about Harmonics?
IN THIS ISSUE
> > New Schneider Electric residential
sensors range
> > EcoStruxure ® arrives at Highbrook
> > Get amongst it with the Crusaders

Cover Story
Effects of
harmonic
distortion:
> > Increased thermal
losses
> > Increased
equipment failures
> > Reduced
productivity
> > Reduced device
lifetime
> > Reduced energy
efficiency
Towards cleaner power
Emerging regulations may see large electricity users come under increasing
pressure to install specialised filtering equipment aimed at improving the
quality of electricity in New Zealand, says Marc Marchal, a clean power specialist
at Schneider Electric.
As with any other country, New Zealand’s
electricity network is “contaminated” by many of
the devices using the power. Such devices, often
called “non-linear loads”, draw current from the
mains with a waveform that contains frequencies
higher than the 50Hz standard. “Increasing levels
of these frequencies actually compromises the
quality of the electricity network”, says Marc,
“contributing to transmission losses. It also
negatively affects the performance of many other
devices or appliances connected to that network.”
The formal name for the polluting phenomenon
is harmonic distortion, and network operators,
understandably, are concerned about it. “It’s
a quirk of electricity and it’s nothing new – it’s
been around since electricity was discovered.
The problem is most acute with large users
of electricity – typically in the industrial and
agricultural sectors which are operating significant
non-linear loads. But it’s also prevalent in large
commercial buildings, which have powerful
heating and ventilation systems and extensive
fluorescent lighting and computer networks.”
Electricity network operators worldwide tackle the
problem by insisting that customers install filtering
technology to eliminate harmonic distortion. Such
filters ensure that the electricity being fed back
into the network remains at 50Hz.
Legislation
As in other countries, says Marc, “New Zealand
has legislation – such as ECP36 – to address
harmonic distortion. But it’s a little dated
and because we have a number of network
operators, a variety of different standards are
being employed. It’s all become impractical
and difficult to implement and enforce.”
That may all be about to change, however,
with the Electricity Engineers Association of
New Zealand (EEA) having had a workgroup
looking into the harmonic distortion issue for
many months and developing new guidelines.
It is encouraging its members (the Utilities and
network operators) to adopt these new guidelines.
“A national set of regulations will significantly
advance the country’s ability to use its energy
more efficiently,” says Marc, “as well as offer
enormous performance benefits to electricity
users.
“Unfortunately there isn't a silver bullet for
mitigating harmonics. The best results are
obtained by careful engineering ensuring
compliance is achieved, while balancing the
cost of the initial investment against ongoing
operational expenditure for the overall solution.”
HV / MV
Industrial
customers
Other industrial
customers
PCC
Public MV Network
(IEC 61000-3-6)
MV / LV
Marc Marchal is a
Systems and Architecture
Engineer at Schneider
Electric. He has worked in
the industry for 25 years
(locally and overseas) and
is recognized as an expert
in AC motor control and
clean power.
Residential
IEC 61000-3-2 /-3-12
MV / LV
Commercial &
Light industries
PCC
IEC 61000-3-12
IEEE 519 - ER G5/4-1
National regulations
Public LV Network
(future IEC 61000-3-14)
Buildings
HVAC
The international landscape for network and product harmonic standards is complex.
Lift
IEC 61000-3-12 EN 12015
Private
LV Network
Equipment
Equipment
Machine 1
Machine 2
(i.e. IEC 61800-3 as guidance)
Schneider Electric News March 2012 3

Cover Story
Cleaning up electrical pollution
A Christchurch City Council pump station has become a showcase model for
tackling a rapidly growing problem in New Zealand – harmonic distortion of the
electricity supply. Schneider Electric’s harmonic filtering technology is a key part
of the solution.
Harmonic
distortion
contributes
to significant
transmission
losses,
compromising the
quality of supply
as well as the
performance and
efficiency of other
equipment on the
same network.
Industry experts often refer to harmonic distortion
as “electrical pollution,” and it has multiple
sources. While it isn’t a new phenomenon,
harmonic distortion has become more prevalent
in the last few years with the rapid growth in the
use of variable speed drives (VSD). VSDs offer
users significant performance and energy benefits,
but they are notoriously enthusiastic generators of
harmonic distortion.
Eliminating the distortion requires the installation
of a “filter” to ensure that the current flowing back
into the network remains at 50Hz. Unfiltered
current presents in many different frequencies,
but engineers say the “fifth harmonic” (250Hz) is
the worst, with the highest transmission losses.
The problem exists throughout the country but
has spiked in rural parts of the South Island
with the growing use of VSDs in the booming
agricultural sector, where the drives control large
motors connected to irrigation pumps. Network
operators are understandably concerned about
the ever increasing impact of harmonics on power
quality. Christchurch-based Orion NZ is one
network operator now demanding the introduction
of harmonic distortion filtering technology –
particularly with customers drawing loads larger
than 22kW. Many agricultural operations fall into
that bracket – as do many of the Christchurch City
Council’s 370 pump stations.
Sockburn Pump Station
Sockburn is one of the Council’s oldest and largest
pump stations and it’s just been upgraded as part
of an overall asset maintenance programme.
Christchurch’s Powell Fenwick Consultants Ltd
designed the new electrical system. The new
technology – including a Schneider Electric
Accusine harmonic filter – allowed extensive
rationalisation. Two switchboards and two
transformers have been replaced with a single
switchboard and a single 750 KVA transformer.
The upgrade also saw the introduction of highefficiency
250kW motors for two of the main
pumps, with two of Schneider Electric’s 250kW
Altivar 61 VSDs to control them. Two other, smaller
pumps are each controlled by 37kW Altivar drives.
An older, direct current motor (with a 164kW thirdparty
DC drive) was retained for the third main
pump.
Standard drives, says Powell Fenwick engineer,
Tim Hughes, “can generate harmonic distortion
levels higher than 30% – and to meet Orion’s
stipulated Total Harmonic Distortion threshold
(THDi) of 9.2%, we opted to install a 300A
Accusine Active filter.”
He goes on to say, “A key advantage of Accusine’s
Active design is its ability to filter all the harmonic
loads in the plant – in this case the AC as well as
the DC drives – collectively, by installing it at the
switchboard. Alternative technologies often require
a filter for each individual drive.
“Furthermore, the Accusine has a built-in power
factor correction capability, allowing us to remove
the power factor correction on the old DC drive, with
the filter keeping the power factor up above 0.95.”
Schneider Electric, he says, offers an excellent
turnkey solution for the installation of the filtering
The Accusine active filter has been installed at the switchboard, providing
harmonic mitigation for the entire plant including two 250kW and two 37kW
Altivar 61 VSDs, and a 164kW DC drive.
Mark Johnson, Controls and SCADA engineering for Christchurch
City Council monitors the Accusine filter performance from the
built-in touch screen HMI.
4 Schneider Electric News March 2012

Cover Story
How do Accusine Active harmonic filters work?
Accusine Active Harmonic filters continuously monitor the harmonic current spectrum on the
electrical network. By dynamically injecting current at opposite phase to the harmonic frequencies,
the filter leaves a near perfect 50Hz sine wave at the supply transformer.
Harmonic
generators
Active Filter
Result
MV
A knowledge of
Accusine’s active
design is its ability
to filter all the
harmonic loads.
2
1,5
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0
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-1,5
-2
+ =
-2
2
2
1,5
0,5 1
1,5
0,5 1
0
0
-0,5 -0,5
-1
-1
-1,5
-1,5
-2
Harmonics
2
1,5
0,5 1
0
-0,5
-1
-1,5
-2
0
2
Harmonic
generators
M
1,5
0,5 1
-0,5
-1
-1,5
-2
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1,5
0,5 1
0
-0,5
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-2
= =
Active
Filter
technology. “We provide the parameters and
specifications for the drives, and their engineers
identify the appropriate filter, install it and
commission it.”
Some 20 pump stations have been upgraded
so far – and many more are earmarked in the
Christchurch City Council’s asset maintenance
programme. Mark Johnson, its Controls & SCADA
Systems engineer, says the organisation has
chosen to standardise on Altivar drives.
“We particularly like the drives’ programmable
pump controller cards. They give operators a far
higher degree of control over the pumps – we can
fine-tune the duty-cycles more precisely, resulting
in greater energy efficiency.”
Filtering technology, he points out, can also
provide advantages for major electricity users
setting up new facilities, “If your new plant has a
1MW load, you’d think a 1MVA transformer would
do the trick. However, to account for the additional
burden and losses caused by harmonic distortion,
electrical design engineers often over-size the
expensive supply transformer and electrical
network infrastructure. With filtering technology,
the bigger transformer might not be required.”
Harmonic mitigation
Solution Handbook
Other distortion sources
Stephen Hirsch, senior engineer at Orion says
that while VSDs generate high levels of harmonic
distortion, they are not the only source of the
problem. “Major office blocks – which typically
have extensive heating and ventilation systems,
fluorescent lighting infrastructures and computer
networks – are equally problematic.”
Such buildings, he says, should also be fitted
with filtering technology – ideally at the main
switchboard – and it will be up to country’s
individual network operators to stipulate and
enforce its introduction.
“Harmonic filtering technology is obviously an
additional cost for users, but it’s important to
understand that left unchecked, the distortion
problem will only get worse and ultimately
compromise the quality of the electricity supply,
network performance and its reliability.”
Do you want to know more?
Download our Harmonic
Solution Brochure today!
Visit SEReply.com and enter
the keycode 44365Y
Schneider Electric News March 2012 5