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Safety Considerations for Smart Grid Technology Equipment

1403 smart-grid coverOne of the biggest frontiers in electrical engineering in this early part of the 21st century is the development and implementation of smart grid technology.

Development of greener technologies and alternative fuels has become a global economic priority, so smart grid technology has the potential to be one of the next great technological waves. It can jump-start stagnated economies, and can fundamentally change the way power is delivered to consumers of electricity worldwide. The environmental benefits that smart grid technology can deliver are collectively demanded by most of Earth’s inhabitants at this time, and the decrease in dependence on fossil fuels and other non­renewable power sources is also sought through this new technology.

Smart grid technology can be viewed as a merging of power systems, information technology, telecommunications, switchgear, and local power generation, along with other fields that were once electrical technologies of separated industries. As these separate technologies become merged, much of the safety considerations will have to be merged and reconciled as well, particularly at interfaces. In some cases, new insight may have to be given to safety that was not necessary in the past.

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This article provides a brief overview of smart-grid technology, and then explores the safety considerations that should be addressed in the design of smart grid technology equipment, particularly in low-voltage AC power applications operating below 1000 V AC. It recognizes smart-grid technology as the merger of power generation, distribution, metering and switching equipment with communication, information technology, and with new user applications. Then, it suggests a modular approach of evaluating the safety of smart-grid technology based on the safety requirements of the individual merged technologies. In addition, examples of some likely smart-grid applications and the safety considerations that would need to be addressed are discussed. It also points out known safety issues with localized electric power generation systems that will be more enabled by smart grid technology.

WHAT IS A SMART GRID?

A smart grid combines the existing electrical infrastructure with digital technologies and advanced applications to provide a much more efficient, reliable and cost effective way to distribute energy. The main function of a smart grid is to manage power consumption in optimal ways, providing the network with more flexibility in case of emergencies. Within the context of smart grids, there are different kinds of supporting technologies, such as smart meters that can help monitor energy consumption and promote more effective distribution.[1]

SMART GRID: WHAT TO EXPECT

Power industry experts look to the smart grid in much the same manner as computer and telecommunications experts looked at the advent of the internet, or “information superhighway” less than a generation ago. It is viewed as the necessary next step in order to modernize the power distribution grids, but there is no single view on what shape or format the smart grid will take.

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Without a doubt, the expectation from the power generation and transmission industry is realization of efficiencies. Better sampling of usage and understanding demand patterns should allow the electric utilities to lower the use of power-generation plants, possibly saving millions of dollars by not having to build new plants to meet increases in power demand. Many of these plants burn coal and other fossil fuels that are non-renewable and greenhouse-gas producing sources of energy, and they are increasingly becoming more scarce and expensive.

ALEXANDER GRAHAM BELL VS. THOMAS EDISON

A popular comparison that points out the magnitude of change in the telecommunication industry as opposed to that of the power industry is to hypothetically transport Alexander Graham Bell and Thomas Edison to the 21st century, and allow them to observe the modern forms of the telecommunications and power industries that they helped create. It is said that Alexander Graham Bell would not recognize the components of modern telephony – fiber optics, cell phones, texting, cell towers, PDA’s, the internet, etc. – while Thomas Edison would be totally familiar with the modern electrical grid [2]. Thus, with smart grid, there is the potential to modernize and advance the architecture of the power systems technology in the 21st century, as the newer technology has already advanced the telecommunications technology.

Still, Mr. Edison would be just as astonished as Mr. Graham Bell with the present power grid technology as it is today. The century-old power grid is the largest interconnected machine on earth. In the USA, it consists of more than 9,200 electric generating units with more than 1 million megawatts of generating capacity connected to more than 300,000 miles of transmission lines.[2] Mr. Edison would not be familiar with nuclear power plants or photovoltaic cells, as these technologies were developed after his death in 1931.

To celebrate the beginning of the 21st century, the National Academy of Engineering set out to identify the single most important engineering achievement of the 20th century. The Academy compiled a list of twenty accomplishments that have affected virtually everyone in the world. The internet took thirteenth place on this list, “highways” were ranked eleventh, but sitting at the top of the list as the most important engineering achievement of the 20th century was the development of the present electric power grid.

A MODULAR APPROACH TO SMART-GRID SAFETY

Since smart grids will involve the merger of new and familiar technologies, it would make sense to take a modular approach to safety. The best way to approach this new, merged technology is to break it down into its component technologies, then use existing or new standards to evaluate safety issues involving the component technologies. That is, rather than develop a single standard for, say, a new electrical service equipment with intelligence, for a smart meter, it would make sense to continue to use the base product safety standard for meters, but plug-in the additional telecommunications and information technology safety modules. Likewise, other product applicable safety modules, such as requirements for outdoor equipment, can serve as supplements or overlays to the base meter standard in this case.

Hazard-Base Safety Engineering Standard IEC 62368-1
IEC 62368-1 is the new hazard-based safety engineering standard covering audio/video, information and communication technology equipment. This state-of-the-art safety standard classifies energy sources, prescribes safeguards against those energy sources, and provides guidance on the application of, and requirements for those safeguards. It uses the “three-block” model for pain and injury from the energy source to the person, with the middle block covering the safeguarding necessary to prevent or limit the harmful energy to a person. [3]

If we agree to take a modular approach to evaluating the safety of the smart-grid technology equipment, then IEC 62368-1 will be well-suited for providing the plug-in modules for evaluating the safety of the information technology and communication circuitry portion of the smart grid equipment.

For example, if we have a smart meter with integral information technology and telecommunication interfaces, you could use the international or locally-adopted safety standard for power meters, then use IEC 62368-1 to evaluate the type of personnel that would require access to the smart meter (“skilled,” “instructed,” or “ordinary”), [3] and then determine the level of safeguarding necessary in such areas as isolation from the power equipment, isolation from the telecommunication equipment, construction of the enclosure as a safeguard against accessibility to shock and containment of fire, and so forth.

IEC 60950-1 Continued Use

For the near term, we would expect to use IEC 60950-1 to evaluate smart grid equipment with communication and information technology circuitry for safety, as well as the required protection and separation from other circuits that they require.[4] This would be until IEC 62368-1 becomes adopted by national standards committees.

IEC 60950-22 for Outdoor Information Technology and Communication Circuits

As both IEC 60950-1 and IEC 62368-1 standards reference IEC 60950-22 as a supplemental standard for equipment installed outdoors. We should expect this standard to be used extensively for smart-grid equipment. This standard provides requirements and considerations for enclosure construction, overvoltage category consideration, and pollution degrees (environmental exposure) associated with information technology and communications equipment installed outdoors.[5]

SAFETY OF UTILITY-OWNED SMART-GRID EQUIPMENT

As is the case today, we would expect safety of utility-owned smart-grid equipment located within the power generation or transmission circuits, up to and including the service conductors to the customers’ buildings to continue to be evaluated for safety in accordance with basic utility-safety standards or Codes. These standards include IEEE C2, “National Electrical Safety Code,” and CSA C22.3, “Canadian Electrical Code, Part III.”

EXAMPLES OF SMART-GRID TECHNOLOGY

Automatic Metering Infrastructure (AMI)

Automatic Metering Infrastructure (AMI) is an approach to integrating electrical consumers based upon the development of open standards. It provides utilities with the ability to detect problems on their systems and operate them more efficiently.

AMI enables consumer-friendly efficiency concepts like “Prices to Devices.” With this, assuming that energy is priced on what it costs in near real-time, price signals are relayed to “smart” home controllers or end-consumer devices like thermostats, washer/dryers, or refrigerators, typically the major consumers of electricity in the home. The devices, in turn, process the information based on consumers’ learned wishes and power accordingly. [2]

Safety Concerns of AMI-Enabled Equipment

We could reasonably expect to see some form of communication interfaces and information technology in some appliances that traditionally would never have had such interfaces (washer/dryers, refrigerators, etc.). With this, we should expect a modular approach in evaluating the safety of these appliances, whereby we evaluate the communication subsystems as we would for communication equipment and information technology equipment (ITE), while the bulk of the appliance is evaluated in accordance with the basic safety standard that normally applies to such appliances. This would mean that either IEC 60950-1 or IEC 62368-1 are used to evaluate the communications and information technology subsystems, and communication links would be classified TNV, limited-power circuits, or the like if metallic, and other non-metallic communication technologies such as optical or wireless would be evaluated accordingly.

EXAMPLE: ELECTRIC VEHICLE POWERING

Email was arguably the “killer app” that most enabled the propagation of high-speed internet. It is not yet known what the smart-grid “killer app” is going to be, but like pre-season predictions of who is going to win the Super Bowl or the World Cup, some think that it is going to be plug-in hybrid electric vehicles (PHEVs) and possibly full electric vehicles (EVs).

As plug-in electric vehicles replace gasoline-only burning vehicles on the market, parking lots will need to be equipped with outdoor charging stations. We would not expect any commercial or government establishments to give away free electricity, so we should expect to see the rise of pay-for-use charging stations, integrating technologies such as electrical metering, switching, information technology, telecommunications, and currency-handling technology.

A pay-for-use charging station might involve the following technologies:

  • An AC-power outlet receptacle to plug in the vehicle for charging;
  • Electric power metering to measure electricity use;
  • Switchgear to switch charging circuits on or off, once enabled by information technology, and provide overcurrent protection or active shut­down in the event of a short-circuit fault in the vehicle’s or the charging circuit’s circuitry;
  • Information technology equipment to process the sale, timing, and user interface to purchase electrical charge, and to enable/disable the charging switchgear;
  • Telecommunications to communicate the sale and power use back to the electrical power retailer. We might expect to have campus-type communications from the charging station to a central control station, and then have a trunk telecommunication connection to the network;
  • Currency handling technology, which might involve direct input of paper or coin currency, credit-card transactions, smartcard or wireless interface, or, quite possibly, cell-phone enabled transactions; and
  • The equipment would be located outdoors and be installed in a weatherproof housing.

Higher Overvoltage Category for Information Technology in Charging Station

The meter safety standard and switchgear standards may assume that these components are installed in Overvoltage Category IV or III environments, but the information technology equipment standard expect equipment to be installed nominally in Overvoltage Category II environments.

According to IEC 62368-1, Annex I (also IEC 60950-1, Annex Z), electricity meters and communications ITE for remote electricity metering are considered to be examples of Overvoltage Category IV equipment, or equipment that will be connected to the point where the mains supply enters the building. “Power-monitoring equipment” is listed as examples of Category III equipment, or equipment that will be an integral part of the building wiring. In these higher overvoltage categories (IV and III), the value of the mains transient voltages is higher than it would be expected for general indoor-use Category II AC-mains connected appliances. This translates into a need for much greater creepage and clearance isolation distances, as well as much higher electric-strength withstand voltages.

Information technology equipment, on the other hand, is generally utilized in Overvoltage Category II environments, or connected to outlets on branch circuits a safe distance away from the service equipment. Also, as the amount of off-the­shelf, commercially-available ITE sub-components increases in the charging station, it becomes more infeasible to simply increase the spacings or the quality of insulation. It may be necessary to use surge protection devices, either integral to the equipment, or externally connected to limit transient voltages from Overvoltage Category III and IV to Overvoltage Category II.

Protection of Communications Circuits

Metallic connections to a telecommunication network would need to be evaluated in accordance with IEC 62368-1 or IEC 60950-1.

Additionally, intra-campus communication conductors, such as those used for intra-system communications or status alarms, will also need to be protected like telecommunication conductors in accordance with the local electrical code or practices. This may mean putting telecommunication protectors—primary (voltage) or secondary (power-cross)– at each end of a campus-run communication conductor where there exist an exposure to lightning or to accidental contact with electric power conductors.

User Accessibility

Additionally, the charging station terminal where the user pays for and plugs in his electric vehicle needs to be made safe so that unskilled persons may use the station. This would require the highest levels of guarding against intentional access to hazardous voltages.

ENERGY STORAGE SAFETY

Locally-generated electrical energy, such as that from photovoltaic systems, needs to be stored during accumulation cycles for use during peak demand cycles. In most cases, this will be achieved by use of DC storage batteries that invert the electrical energy to AC for local use or for sale back to the electric company. Battery technologies such as lithium ion or valve-regulated lead acid batteries are the most likely present technologies to be used, though advanced batteries such as sodium batteries may be considered.

The size and capacity of these battery storage systems would historically have been found in commercial or industrial installations where only service personnel would have access. Now as part of smart grid and green-power initiatives, you can expect to see such systems in residential locations where anyone might have access.

Safety issues to be considered include:

  1. Prevention of access to live parts at high electrical energy levels;
  2. Prevention of access to live parts at shock potentials;
  3. Ventilation of batteries that outgas explosive gases, such as hydrogen from lead-acid batteries.
  4. Containment of batteries capable of producing excessive heat during breakdown or thermal runaway.
  5. For outdoor applications, suitably housing the batteries in an outdoor enclosure that, if equipped with lead-acid batteries, is well ventilated in accordance with IEC 60950-22 to prevent the accumulation of explosive gases.

OTHER SAFETY CONCERNS – LOCAL POWER GENERATION

Local power generation systems, such as photovoltaic systems, generators, fuel-cell systems, and the like, for which the smart grid will permit the sale of power back to the utility, involve the following safety concerns:

Synchronization

The frequency of the locally-generated power has to be synchronized with that of the main grid.

Islanding

Islanding is a condition in which a portion of an electric power grid, containing both load and generation, is isolated from the remainder of the electric power grid. When an island is created purposely by the controlling utility—to isolate large sections of the utility grid, for example—it is called an intentional island. Conversely, an unintentional island can be created when a segment of the utility grid containing only customer-owned generation and load is isolated from the utility control.

Normally, the customer-owned generation is required to sense the absence of utility-controlled generation and cease energizing the grid. However, if islanding prevention fails, energized lines within the island present a shock hazard to unsuspecting utility line workers who think the lines are dead.[6]

CONCLUSION

The smart grid promises to bring on a new age of distributing electricity in more efficient and greener ways, while enabling the developing of new ways to efficiently utilize and control power.

In many ways, it will take the form of a merger of power generation, distribution, switching, and metering technology with communications and information technology, along with other applications of electrical energy. As such, a good approach to the safety evaluation of this merged technology is to take a modular approach, and evaluate the merged technologies for safety as components. Furthermore, IEC 62368-1, the new international hazard-based safety engineering standard for audio/video, information and communication technology is well-suited for use in this modular-safety approach. favicon

REFERENCES

  1. B. Metallo, “Smart Grid. Smart Decision,” 2010, unpublished internal Alcatel-Lucent article.
  2. “The Smart Grid: An Introduction,” prepared for the U.S. Department of Energy by Litos Strategic Communications under contract No. DE-AC26­04NT41817, Subtask 560.01.04.
  3. IEC 62368-1, Edition 1.0, 2010-01, “Audio/Video, Information and Communication Technology Equipment – Part 1: Safety Requirements,” International Electrotechnical Commission.
  4. IEC 60950-1, Edition 2.0, 2005-12, “Information Technology Equipment – Safety- Part 1: General Requirements,” International Electrotechnical Commission.
  5. IEC 60950-22, Edition 1.0, 2005-10, “Information Technology Equipment – Safety- Part 22: Equipment to be Installed Outdoors,” International Electrotechnical Commission.
  6. IEC 62116, Edition 1.0 2008-09, “Test Procedure Of Islanding Prevention Measures For Utility-Interconnected Photovoltaic Inverters, ” International Electrotechnical Commission.
author gies-don Don Gies has been a product compliance engineer for over 25 years. Since 1989, Mr. Gies has worked at AT&T-Bell Laboratories/Lucent Technologies/Alcatel-Lucent as a product safety engineer, responsible for obtaining product safety certifications for his company’s telephone and information processing equipment from domestic and international product safety organizations.<

Mr. Gies has become a leading subject matter expert for his company in the field of global product safety compliance, working primarily with Alcatel-Lucent’s wireless base station equipment. He is a member of the Alcatel-Lucent Technical Academy. Prior to working at AT&T, Mr. Gies was a Tempest engineer for Honeywell-Signal Analysis Center, where he worked on various secure communications projects for the US Army Communications -Electronics Command.

Mr. Gies graduated from Rutgers University – College of Engineering as an electrical engineer. He is an iNARTE Certified Product Safety Engineer.

 

 

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