ringing SmartGrid on the Factory and Automation Floor
A. MCEACHERN1, Power Standards Lab (US), alex@powerstandards.com
A. EBERHARD, Power Standards Lab (US), aeberhard@powerstandards.com
Abstract
This paper introduces a new application for Power Quality and Energy Monitoring:
embedding power quality monitors inside sensitive industrial, commercial, automation,
manufacturing and medical equipment – and bringing SmartGrid to the factory and
automation floor.oor. Using power quality monitors to solve intermittent problems has also been
limited by the cost of monitors. In this case, the monitors are generally installed at the
equipment terminals. So the monitors can either directly interface with the load, or they can
interface via e-mail or WebServer with a remotely connected user. In addition the new
technology also combines a high accuracy energy monitor that can precisely control loads
based on the load profile.
It also introduces IEC 61000-4-30 which is an excellent standard that ensures that all
compliant power quality instruments, regardless of manufacturer, will produce the same
results when connected to the same signal. However, instruments that comply with the Class
A requirements of this standard have, until now, been too expensive for common use. Now a
new set of technologies developed by an American company, in cooperation with a
Japanese company, demonstrate that it is possible to manufacture three-phase power quality
instruments that are fully compliant with the Class A requirements of IEC 61000-4-30, and to
do so at ultra-low-cost, allowing these monitoring devices to be used even at entry levels of
individual loads.
Keywords
Power Quality, Instrument, SmartGrid, New Measurement Technology, Meter, Low Cost,
Monitoring, PQube, IEC 61000-4-30
1. INTRODUCTION
Traditionally, power quality instruments have been complex and expensive – often several
thousand Euro.
The cost of power quality instruments is driven by five factors:
1. The cost of developing the instruments
2. The quantity of instruments produced – the more instruments that are produced, the
lower the development cost in each instrument
3. The cost of manufacturing the instruments
4. The cost of installation, especially the cost of the communication infrastructure
5. The cost of supporting the instruments, especially the cost of supporting special-
purpose software, throughout the life of the instruments.
Remarkably, in the last few years, all of these costs have been driven down simultaneously.
This paper describes the technologies in a new, ultra-low-cost power quality instrument, and
explains why the costs are so low.
2. REDUCTION IN DEVELOPMENT COSTS
Traditional power quality instruments were developed, from the start, as special purpose
instruments. Hardware, firmware, and software were all developed specifically for that instrument.
However, several developments in other, unrelated industries have made that approach unnecessary.
First, the wide-spread development of digital audio (mobile phones, mobile music players,
digital television, etc.) has led to rapid developments in the DSP (digital signal processor)
field. New DSP chips are inexpensive, use minimal power, and have built-in analog-to-digital
and digital-to-analog conversion. Best of all, they are optimized for processing multiple
channels of 20 Hz to 20 kHz signals. By coincidence, power quality measurements are
generally made between 50 Hz and 3 kHz – right in the middle of the optimum band. The
popularity of the iPod® has resulted in cheaper, better power quality monitors.
Second, the development of relatively complex portable devices (PDAs, mobile phones that
also have computer functions, digital cameras, etc.) means those extremely tiny, highly
reliable electronic devices are now readily available: connectors with large numbers of pins,
tiny op amps, and passive components like resistors and capacitors. Tiny means cheap, in
general, if the manufacturing is completely automatic.
Figure 1: Reduction in component size. Smaller components reduce
costs in several ways: smaller printed wiring boards, smaller plastic
packages, even smaller power supply requirements. The packages
shown are, from left: through-hole DIP, surface mount, and BGA, or
ball-grid-array.
Third, the availability of high-voltage (1kV), low-current op amps, which
are generally used for driving submarine sonar transducers, means
that automatic test equipment for power quality instruments can be
developed far more cheaply now.
Finally, software standards for file structures – as in digital cameras – mean that power
quality instrument developers no longer need to define and support their own file structures.
In fact, Windows® text files and web-based graphic file formats have become virtually
universal.
Of course, some very difficult problems must still be solved by the instrument engineer. How
should one deal with a 6kV lightning impulse in such a tiny package? How can one meet the
creepage and clearance requirements in the safety standards? Most important of all, a
power quality instrument must, by definition, work when the power is bad, and other
electronic devices are failing. How can an engineer design an instrument that survives
conditions that other instruments can’t? But all of these difficult challenges can be met.
3. INCREASE IN THE QUANTITY OF POWER QUALITY INSTRUMENTS
Traditionally, each country defined its own power quality instrument requirements. This
meant that an instrument optimized for France, for example, was unlikely to find acceptance
in Brazil, for example. Sometimes the situation was even worse: each electric power
company would define its own requirements for power quality measurements.
As a result, the production quantity for each instrument design was small, and the fraction of
the development cost carried in each instrument was large. A rough example: If developing
an instrument costs 1.5 million Euros, and the total expected market is 2000 instruments,
each instrument must carry 750 Euros of development costs – a significant but not
uncommon burden. Recent IEC standards [1][2][3][4] have solved this problem.
IEC 61000-4-30[1][2], in particular, has defined power quality measurement methods. Class
A in this standard ensures that any two instruments, when connected to the same signal, will
produce the same result. Figure 2 and Figure 3 give examples.
Figure 2. Example of one of the problems solved by IEC 61000-4-30. In this graph of RMS
voltages, what is the duration of the voltage dip? The answers shown range from 0.5 seconds to 4
seconds, and all of them are technically correct.
Simply by designating one of these answers as the requirement (4 seconds for dip duration
measurement, 0.5 seconds for interruption duration measurement), IEC 61000-4-30 reduces
cost of instrumentation.
Figure 3. Example of another problem solved by
IEC 61000-4-30. Is this dip 50% for two cycles, or 0% for 1 cycle? Again, both answers are
technically correct. IEC61000-4-30 makes it clear that this is a dip to 0% for 1 cycle – thus reducing
cost of instrumentation.
As a result of this IEC standardization, an instrument can be designed for worldwide
acceptance, allowing much higher total production quantity. This means that the
development cost burden is much smaller.
4. DECREASE IN MANUFACTURING COSTS
Globalization has driven manufacturing costs down.
It is now easy to choose the best sources for parts, worldwide. For example, in the initial
product shown in Figure 4, the lower case comes from Germany, the upper case comes from
the United States, the display and the memory come from Japan, and the internal electronics
are automatically assembled in California using parts from the U.S., Ireland, China, Japan,
and other countries.
Figure 4. Initial Design of a three-phase, voltage-and-current,
IEC 61000-4-30 Class A-compliant power quality monitor. The
digital camera influence can be seen in the SD memory card,
which holds up to 4 GB of data. Standard DIN-rail mounting
means installation is cheap and quick. The name of this new
device: PQube. Power Quality in a little cube.
Fully automated manufacturing (robots for placing parts, automatic testing systems for
verifying that boards are working properly, automatic calibration systems that adjust internal
digital constants, etc.) means that manufacturing costs can be kept very low, even in
locations with high labour costs like California, without any sacrifice in quality. Indeed, the
quality of products manufactured in environments with highly automated production and test
procedures is generally higher than products that are produced in regions with low labour
costs and low automation.
Figure 5. Probes for parameters that may be related to power quality are
included in the package: temperature, humidity, barometric pressure, etc.
A GPS satellite receiver ensures precise timing.
5. DECREASE IN INSTALLATION AND COMMUNICATION COSTS
Traditional power quality instruments come with their own unique packaging design.
However, they are not always suited for their typical locations, usually where there are lowvoltage circuit breakers.
By packaging the power quality instrument in a standard 35mm DIN-rail circuit breaker
package, installation is greatly simplified.
Perhaps more important, the communication cost of an installed power quality instrument,
over the life of the instrument, often exceeds the cost of the instrument itself. Whether the
communication is via Ethernet, or telephone modem, or short-distance radio, bringing the
communication signal to the monitoring point is a significant cost.
(We should not forget the additional hidden cost of the damage that can be caused to the
communication network during major power disturbances. In regions with strong lightning
activity, for example, telephone modems typically become damaged through their connection
to power quality monitors.)
The featured new little product has innovative communication ability. The unit shown in
Figure 4 supports Ethernet connectivity (and includes a web server, an FTP server, and an
email generator), wireless radio connectivity, and a modem connection. However, it is fully
functional without connectivity – it can easily store years of data on a removable SD memory
card.
6. DECREASE IN THE COST OF SUPPORTING POWER QUALITY INSTRUMENTS
Although it is often hidden from the end user, the lifetime support cost for traditional power
quality instruments is significant.
This is especially true for the special-purpose software that was written for each instrument.
Often, this software was written for Windows®; and the lifetime of a power quality instrument
greatly exceeds the lifetime of one release of Windows®. For example, many power quality
instruments that are still in use were originally issued with Windows® 3.1 software.
The lifetime costs of upgrading and supporting this software was a major cost.
Fortunately, such software is no longer necessary. By following the software-free model of a
digital camera, the prototype power quality instrument of Figure 4 requires absolutely no
software. When you connect a digital camera to your computer, you immediately see the
pictures in a folder on your disk drive. The same is true for power quality data in the
prototype instrument.
By eliminating the need for any software at all, power quality monitors like the little PQube
above drive down the costs even further.
Figure 6. A typical event graph that is
generated by the little PQube – Power Quality and Energy Monitor. These kind of
graphs are generated without any software. Picture shows typical voltage sag
Again, this does not eliminate all firmware challenges. The instrument firmware must still
support a wide variety of languages and character sets (Japanese, Korean, etc.), and the
.CSV (comma-separated values) files for spreadsheets must work with European systems
that use the comma symbol for other purposes. But all of these problems have been
previously solved in digital cameras and the solution incorporated in the power quality
instrument above
7. Conclusion
Recent changes in standards and technology have made it possible to produce an IEC
61000-4-30 Class A power quality instrument at a very low cost. It is also small enough to be
integrated into larger electrical equipment and control panels.
8. Biographies
1Alex McEachern is well known for his cheerful, thought-provoking
speeches, and he regularly speaks at national and international
conferences
on electric power quality. He is the president of Power Standards Lab in
California, the founder of BMI, the former president of both BMI and
Electrotek, and the author of everything from the Electric Power
Measurements chapter of the Encyclopedia of Electrical and Electronics
Engineering to the industry-standard Handbook of Power Signatures. Active
in drafting and approving international power standards, Alex is the
chairman of the International Electrotechnical Commission (IEC) TC77A Working Group 9,
which sets the standard for power quality instruments. He also participates in the drafting of
the voltage dip immunity standards, IEC 61000-4-11 and IEC 61000-4-34. He is a Senior
Member of the IEEE, former Chairman of IEEE 1159.1, a co-author of IEEE 519 and IEEE
1459, and a voting member of the IEEE Standards Coordination Committee on Power.
Andreas Eberhard is well known in the international testing standard
andpower quality community. He is member of various power quality and
safetystandard committees around the world. He used to work for more than
ten years with TUV Rheinland in Europe, Asia and the US before he joined
Power Standards Lab in 2005. Andreas holds two Master Degrees
(Electrical Engineering and Technology Management) from Universities in
Europe and the United States. His latest work and studies are related to the
impact of renewable energies on grid stability. With PSL he did develop and design a new
Power Quality and Energy measurement technology. This innovative technology will improve
and change the way how Power Quality and Energy was traditionally monitored. Andreas is
also a co-author of the Intech Power Quality Book that was published in 2011.
He is Vice President of Technical Services at Power Standard Labs and can be contacted at
aeberhard@powerstandards.com, or Tel ++1-510-522-4400.
Acknowledgement
(1)The above-named main author (McEachern) is the Convenor of IEC TC77A Working
Group 09, which is responsible for maintaining IEC 61000-4-30 Power Quality Measurement
Methods. We gratefully acknowledge the useful and knowledgeable technical contributions of
members of this Working Group during discussions and exchanges over the last 10 years.
Any errors that remain in this paper are entirely the responsibility of the authors.
Literature
[1] IEC 61000-4-30, Ed 1, “Testing and Measurement Techniques – Power Quality
Measurement Methods.” International Electrotechnical Commission. February 2003.
[2] Corrigendum 1, IEC 61000-4-30, Ed 1. August 2006.
[3] IEC 61000-4-15, Ed 1.1, “Flickermeter – Functional and Design Specifications.”
International Electrotechnical Commission. 2003.
[4] IEC 61000-4-7, Ed 2, “General Guide on Harmonics and Interharmonics Measurements
and Instrumentation.” International Electrotechnical Commission. 2002.
