Comment on the “Draft Guide for Harmonic Limits for Single-Phase Equipment”, P1495/D1, 01-28-00
TO: Patrick Coleman
Alabama Power
Single Phase Harmonics Task Force
IEEE PES/Transmission and Distribution Committee
7/10/00
From: Robert E. Gardinier
Member, IEEE PES
Member, U.S. Technical Advisory Group, IEC 77A
Member, IEC 77A, WG1, TF1, TF1a, TF5a, TF5b
Subject: Comments on the draft guide for harmonic limits.
Reference: “Draft Guide for Harmonic Limits for Single-Phase Equipment”, P1495/D1,
1/28/00
Patrick,
Per our email notes, please find attached comments in regard to the reference document.
My comments are intended to be constructive and to assist with the development process.
Please feel free to share these comments with anyone that has an interest in the development of
this guide.
I am looking forward to the discussion of this draft document at the PES meeting on Tuesday,
7/18/00 in Seattle.
Regards,
Bob Gardinier
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R. E. Gardinier
Comment on the “Draft Guide for Harmonic Limits for Single-Phase Equipment”, P1495/D1, 01-28-00
Overall Comments
The guide addresses products that represent future non-linear loads that will be attached
to the public low voltage network, which may cause harmonic voltage compatibility
levels to exceed some acceptable level. The object is to “arrive at a reasonable set of
limits for single-phase equipment such that the likelihood of a problem caused by
harmonics is small”. Participation by product manufacturers is essential to meeting these
objectives and to arrive at a guide that will have the right balance to achieve the lowest
cost to society at the same time it achieves the desired effect of protecting the public low
voltage network.
A rationale that justifies the need for limits at any level is currently missing from the
document. The limits proposed in Section 7.6 of a maximumTHD of 15% for all products
, with a maximum 3rd harmonic current of 10%, are totally unjustified and there is
insufficient evidence given in this document, or can be found anywhere in the current
literature, that supports such extreme limits. It would require that active power factor
correction circuitry be added to most electronic equipment manufactured today in order
to meet these limits. There is no justification for the need to impose this added cost
burden on society, or that this is the most cost effective approach to solving a potential
future problem.
An additional list of references has been added and they are referred to throughout the
comments where appropriate. Some of these references are duplications to those that are
contained within the draft guide but are included here for continuity.
Comments by Section
Overview(1.)
Before we attempt to set limits to solve a problem that has not been completely defined,
we need a better definition of the problem.This includes continues monitoring of the low
voltage network to determine the current levels of harmonic distortion and the rate of
growth of the harmonic levels over time. We also need to have a better understanding of
the combined effect of a mixture of non-linear loads and linear loads distributed within
premises, and within a network.
Scope(1.1)
The scope should be consistent with the United States National Committee Position Paper on
power line harmonics [1] and be limited to high impact products that can be identified as
having a high potential of causing problems on the low voltage network and which can
not be addressed by IEEE 519.
Not all products may need to have limits because of a combination of their power level,
market penetration, usage time, etc.. These products, that have low impact, should not
require limits. Products that have medium impact on the network should have limits that
are less restrictive than high impact products.
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R. E. Gardinier
Comment on the “Draft Guide for Harmonic Limits for Single-Phase Equipment”, P1495/D1, 01-28-00
Purpose(1.2)
If we want “To establish equipment harmonic limits, much like IEC 6100-3-2”, we
should align the effort with the IEC such that the limits that we establish can become a
subset of the IEC 61000-3-2 limits for those products that require limits. Our objective
should be “One set of Limits, One measurement method, One label” Worldwide. Product
manufacturers are already burdened with an endless list of requirements, measurement
standards, and labeling requirements. We should not be adding to this costly burden by
creating a unique set of requirements.
The existing 519 standard does provide guidelines for harmonic levels and can be used to
determine mitigation requirements at the premise level.
Loads covered in this standard(4.0)
The guide should limit its coverage to non-linear loads that use technology topologies
that have the potential to have a high impact on the network and where network field data
has demonstrated that these loads will cause an unacceptable increase in the harmonic
levels of the network.
Background(5.0)
This section presents expressions that can be used to determine the approximate amount
of harmonic current present and expressions used to determine the total harmonic
distortion in percentage. There does not appear to be need for this information in this
document.
Existing Related Industry Standards and Practices(6)
IEEE 519(6.1)
No Comments
IEC 61000-3-2 and IEC 61000-3-4(6.2)
IEC 61000-3-2 is currently undergoing a complete revision with a completion target of 2004.
In addition, key amendments[13} are being voted on at this time that enhance the measurement
method and modify the classification of products that are subject to proportional limits when this
standard goes into effect on 1/1/2001.
This standard is an example of what can happen when manufacturers are not involved and the
concerns of manufacturers are not properly taken into consideration throughout the development
of the standard. Any standard that sets requirements for the product manufacturers must have
participation by the manufacturers.
The measurement detail required by these standards is also unacceptable. Individual harmonic
current levels are required up through the 39th harmonic. The approach suggested in this draft
guide is to use the total harmonic distortion(THD) as a limit method. This has merit and should be
considered. It allows for more flexibility in individual harmonic levels, which will allow
manufacturers more design freedom in meeting the limits. Individual harmonic limits may be
required in some unique situations.
Recommended Distortion Limits(7)
Although there have been studies done on specific load types, there has not been a significant
number of studies done that use a diverse set of loads that might represent typical loads on a low
voltage network when servicing residential, commercial, or industrial installations.
The impact factors of all the loads on a given network including power level, harmonic content,,
usage (time of day, hours per day, etc.), market penetration and the respective interaction of the
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R. E. Gardinier
Comment on the “Draft Guide for Harmonic Limits for Single-Phase Equipment”, P1495/D1, 01-28-00
loads must be considered when setting limits. This includes attenuation, cancellation, current
division, and diversity.
Differences in Distribution Design(7.1)
Definition of the equivalent impedance of the U.S. power distribution network is important to
setting harmonic limits. Task Force 5b of TC77A/WG1 has been given the responsibility of
defining the network impedance in North America(U.S., Canada, Mexico) and Japan. The findings
to date indicate that the impedance(Z) relationship between locations has the following
relationship: ZEurope>ZJapan>ZNorth America at the point of common coupling(PCC). These findings are
in disagreement with what is stated in this draft. This area obiviously needs further study and
definition to make certain that we are all reading from the same page.
The findings of TF5b also indicate that the network impedance is primarily a function of the
network architecture and system design strategy. The U.S. and Canadian networks appear to be
more robust in general and therefore will have a lower impedance which will make them less
susceptible to harmonic loads. This is also in disagreement with statements made in this section
of the draft.
Consideration of Multiple Nonlinear Loads(7.2)
The considerations outlined in this section are a good starting point for determining what products
may warrant no limits, medium limits, or more severe limits. All of the effects of multiple non-linear
loads combined with linear loads must be considered when establishing limits. The draft has
outlined some of these effects. In addition to diversity effects[3] and cancellation effects[2,6,10],
current division effects[10] and attenuation effects[2,3,4,7,11] most be considered.
Diversity Effects(7.3)
Agree/No Comments
Cancellation Effects(7.4)
Agree/No Comments
Load Levels and Harmonics(7.5)
Agree. Fluctuating loads can have a large dynamic power level and diverse harmonic current
content. The measurement procedure contained within the original draft of IEC 61000-3-2 was
inadequate to handle these types of loads. A major improvement has been defined and is
included in the current amendments[13] to IEC 61000-3-2.
Limits(7.6)
Before limits can be established we must establish network compatibility levels/network
susceptibility levels, current network distortion levels and trends, mitigation alternatives in the
network that may be more cost effective, as well as a network model that considers all of the
network effects. There is absolutely no justification given in this draft document for the
maximum recommended distortion levels given in Table 7-1. These levels are extremely
low and can not be justified from either a technical need or the overall cost to society[1].
Testing Requirements(8.0)
The measurement of harmonic voltages and currents can become very complex when
considering all of the possible load characteristics from quasi-steady state to fluctuating loads.
Sophisticated, and expense, instrumentation is required to make many of these measurements.
Our goal should be to establish measurement parameters that will provide the required level of
control of the harmonic distortion needed to protect the network and which can be measured
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R. E. Gardinier
Comment on the “Draft Guide for Harmonic Limits for Single-Phase Equipment”, P1495/D1, 01-28-00
most economically. The consideration of using THD is a step in this direction and should be
explored further.
Background(8.1)
The product information that is required is provided by product manufacturers. Today, worldwide
regulations require an almost endless list of information and labeling of products. We need to be
careful not to ask for more unique regulations and information than is absolutely needed in order
to connect a given product to the public low voltage network.
Most manufacturers do have information on the non-linear characteristics of their products. This
information may not have been taken from a statistically valid sample size, or production level
products, and therefore should not be used as a public statement of the product’s characteristics.
However, to require manufacturers to provide such information would add another set of
measurement sampling plans, which would add significant manufacturing cost to a product. It
should be sufficient to state that a product meets a given limit, if a limit is required. There may be
a need to have more detailed information for high power loads that represent a very large point
source but not for low power consumer products.
The voltage supply & Harmonic Analyzer(8.2 & 8.3)
It is important to control the source impedance(reference impedance) and the linearity of
the voltage supply when making harmonic voltage and current measurements.
Most product manufacturers have such sources and analyzers available to do harmonic
testing as well as other required test. Considerable work has been done by IEC
committees in regard to harmonic test requirements measurement techniques[14]. This
work should be consulted as a starting point.
Transducers(8.4-8.4.4)
No Comments
Suggested Protocol(8,5)
No Comments / Suggest that reference [14] be used as a starting point.
Respectfully submitted,
R. E. Gardinier, 7/10/00
References:
1. United States National Committee- Power Line Harmonics Position Paper
USCCEMC 99-01 ( May 19, 1999)
2. “Analysis of Compensation Factors Influencing the Net Harmonic Current Produced
by Single-Phase Non-Linear Loads”, International Conference on Harmonics and
Quality of Power(ICHQP) ’98, October 14-16, 1998, A. Mansoor, W. M. Grady
3. “An Investigation of Harmonics Attenuation and Diversity Among Distributed
Single-Phase Power Electronic Loads”, IEEE Transactions on Power Delivery, Vol.
10, No. 1, January 1995, A. Mansoor, W. M. Grady, A. H. Chowdhury, M. J.
Samotyjbb
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R. E. Gardinier
Comment on the “Draft Guide for Harmonic Limits for Single-Phase Equipment”, P1495/D1, 01-28-00
4. “Predicting the Net Harmonic Currents Produced by Large Numbers of Distributed
Single-Phase Computer Loads”, IEEE Transactions on Power Delivery, Vol. 10, No.
4, October 1995, A. Mansoor, W. M. Grady, P. T. Staats, R. S. Thallam, M. T. Doyle,
M. J. Samotyj
5. “A Statistical Analysis of the Effect of Electric Vehicle Battery Charging on
Distribution System Harmonic Voltages”, IEEE Transactions on Power Delivery,
November 25, 1996, P. T. Staats, W. M. Grady, A. Arapostathis, R. S. Thallan.
6. “Harmonic Cancellation by Mixing Non-Linear Single-phase and Three-phase
Loads”, IEEE Transactions on Power Delivery, January , 1998, S. Hansen, P. Nielsen,
F. Blaabjerg; Danfoss Drives/Denmark
7. “Mains Harmonics Analysis of the contribution of TV Receivers”, European
Association of Consumer
Electronics Manufacturers(EACEM), EACEM
Technical Report No. 20, October, 1996
8. “Light Dimming Controls – Justification Supporting Continued Exemption from
Harmonic Limits in IEC 61000-3-2”, Lutron Electronics Co., Inc, 17 September,
1999, D. G. Luchaco, R. S. Spehalski
9. “An Evaluation of Energy Storage Techniques for Improving Ride-Through
Capability for Sensitive Customers on Underground Networks”, IEEE Transactions
on Industry Applications, Vol. 33, No. 4, July/August, 1997, C. J. Melhorn, A. Braz,
P. Hofmann, R. J. Mauro
10. “An Examination of the Rationale for Limiting Harmonic Emissions from LowVoltage Equipment”, IEEE Symposium, 1999, A. Mansoor, J. McKim
11. “Analysis of Harmonic Distortion Levels in Commercial Buildings”, Proceedings of
the First International Conference on Power Quality, PQA, 1991, R. Zavadil, G.
Hensley, K. Johnson.
12. “THOMSON MultiMedia Input – A Collection of Comments, Data Reports,
Memorandums, and Analysis on Harmonics and the Cancellation effects of TV
receivers.”, Harald Grellmann, 1996
13. “Electromagnetic Compatibility(EMC)-Part 3-2: Limits – Limits for harmonic current
emissions(equipment input current up to and including 16A per phase”, EN 61000-32 : 1995/prA14:2000
14. “Testing and measurement techniques – Section 7: General guide on harmonics and
inter-harmonics measurements and instrumentation, for power supply systems and
equipment connected thereto”, EN 61000-4-7 : 1993
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R. E. Gardinier