September 2013

The planning and performance of any reliability based maintenance program has always created challenges regarding methodology and frequency of test, contractor qualifications and selection, as well as regulatory and standards interpretation and implementation. Debate also revolves around the effectiveness of on-line predictive maintenance strategies and preventative programs that impact uptime.

With this said, one of the hardest line items to justify in the budget “prove up” is electrical system maintenance and its impact on the reliability to the wind plant. Many components of these electrical systems, including the turbines, were not designed for the ease of maintenance programs. This can be complicated when third-party engineering review and acceptance testing is not included in the development process. Many electrical projects, whether for normal equipment service or even for safety related maintenance, can come with unplanned costs that exceed budgets and create havoc with project cash flow. Additionally, simple test methodology and contractor selection errors as well as poorly implemented maintenance strategies create costly and possibly catastrophic outages. So what do you do? You have to build a “Cover Your Assets” strategy that protects the electrical equipment and systems, the electrical workers as well as the other stakeholders.

This article is the first of an occasional three-part series that will offer the wind plant owner, designer, developer, and operator some fresh insight—through the eyes of a field-savvy, NETA accredited third party electrical maintenance organization and an EASA-qualified machine repair facility—on how a safety- and reliability-driven electrical protection plan can be developed, documented, and implemented. Each article will be centered wind industry specific challenges:

Part 1—Wind farm electrical specification and installation practices that impact long term reliability and personnel safety.
Part 2—Wind farm electrical practices that impact the turbine and its related components. Not to include the collector system or substation.
Part 3—Wind farm electrical practices that impact the balance of plant to include collector system, substation and the interconnect substation.

Facing Reality
If the safe, reliable operation of a newly-installed electrical power system and related components is to be achieved, several key components are required:

1. The power system and components must be designed and engineered correctly by a qualified firm that considers maintenance practices, personnel safety and long term reliable operation during the specification and planning process.
2. Only proven quality, design tested and defect free electrical equipment should be specified and procured.
3. The installation must meet all applicable codes and standards and be performed by qualified contractors and vendors.
4. Verification of all of the above should be performed through an independent, third-party inspection process, especially in the absence of AHJ personnel.
5. All information should be documented and archived for future engineering, repair, replacement, upgrade or expansion needs.

Although it sounds pretty simple, these steps often don’t happen on an electrical construction project, especially one that is at a remote location.

Standards and Recommended Practices
Consensus technical standards and recommended practices are usually developed to establish uniform engineering criteria and practices that help with compatibility, reliability, and safety. The utilization of these standards helps ensure proper design and construction. Some of the applicable standards and regulations that should be considered are listed below, but there are many others.

Figure 1

OSHA—Occupational Safety and Health Administration (OSHA) was established to “assure safe and healthful working conditions for working men and women by setting and enforcing standards and by providing training, outreach, education and assistance”. The agency is also charged with enforcing these regulations.

NFPA—The National Fire Protection Association (NFPA) creates and maintains standards and codes for use and adoption by local governments that cover a wide range of topics from model building codes to the firefighting equipment.

Especially crucial for wind plant maintenance consideration is the NFPA 70B, which explains the importance of electrical equipment maintenance, as well as  the 70E, which addresses arc flash and the electrically safe working environment.

Current NFPA Standards:

• NFPA 70 — National Electrical Code
• NFPA 70B — Recommended Practice for Electrical Equipment Maintenance
• NFPA 70E — Standard for Electrical Safety in the Workplace
• NFPA 72 — National Fire Alarm and Signaling Code
• NFPA 101 — Life Safety Code
• NFPA 704 — Standard System for the Identification of the Hazards of Materials for Emergency Response
• NFPA 921 — Guide for Fire and Explosion Investigations
• NFPA 1001 — Standard for Fire Fighter Professional Qualifications
• NFPA 1123 — Code for Fireworks Display
• NFPA 1670 — Standard on Operations and Training for Technical Search and Rescue Incidents
• NFPA 1901 — Standard for Automotive Fire Apparatus

NEC—The National Electrical Code (NEC), while having no legally binding regulation as written, can be and often is adopted by states, municipalities and cities in an effort to standardize their enforcement of safe electrical practices within their respective jurisdiction.

AHJ—The authority having jurisdiction (AHJ) is the governmental agency or sub-agency which regulates the construction process where the site is located.  They often have their own standards that should be considered during the system design process.

NESC—The National Electrical Safety Code (NESC) or ANSI Standard C2 is a United States standard of the safe installation, operation, and maintenance of electric power and communication utility systems including power substations, power and communication overhead lines, and power and communication underground lines. It is published by the Institute of Electrical and Electronics Engineers (IEEE).

Planning for Maintenance
Maintenance planning of the electrical equipment and systems should begin at the inception of the project. Consideration should be given to crucial elements such as logistics, access, and equipment configuration, as well as ease of electrical and mechanical isolation. Often the question is asked, “Why test ‘new’ electrical equipment?” Since the protection of both personnel and the electrical systems is so critical at startup of the plant, verification of proper operation is required. Third-party electrical acceptance is the best manner of confirming the safe performance of the electrical system and its specific components. The test data also provides baseline information that is important to a good maintenance regime.  Two general categories of tests are useful.  The first—acceptance testing—verifies that all is well at startup. Maintenance testing is used periodically to assure continued reliability, regardless of the operation methodology chosen for the wind plant. The International Electrical Testing Association (NETA) defines these categories as ATS and MTS.
Figure 2

NETA ATS—Acceptance tests are not manufacturer’s factory tests. They comprise those tests necessary to determine that the electrical equipment has been selected in accordance with the engineer’s requirements, installed in accordance with applicable codes and installation standards, and perform in accordance with their design and setting parameters. The ANSI/NETA Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems assists designers, specifiers, architects, and users of electrical equipment and systems in requesting the required tests on newly installed power systems and apparatus—before energizing—to ensure that the installation and equipment comply with specifications and intended use as well as with regulatory and safety requirements.

NETA MTS—Maintenance tests help determine if electrical equipment is suitable for safe and continued service. When dealing with service-aged equipment, many criteria are used in determining what equipment is to be tested, as well as the intervals and extent of the testing. Ambient conditions, availability of down time, and maintenance budgets are but a few of the considerations that go into the planning of a maintenance schedule. The owner must make many decisions each time maintenance is considered. It is the intent of the ANSI/NETA Standard for Maintenance Testing Specifications for Electrical Power Distribution Equipment and Systems to list a majority of the field tests available for assessing the suitability for continued service and reliability of the power distribution system.

Some suggested sources for maintenance strategies are the IEEE STD 902-1998 (Yellow Book): IEEE Guide for Maintenance, Operation and Safety of Industrial and Commercial Power Systems; NFPA 70B: Recommended Practice for Electrical Equipment Maintenance; or NETA MTS-2011: Standard for Maintenance Testing Specifications for Electrical Power Equipment and Systems. The NETA testing standard also offers guidelines for the frequency of maintenance tests within “Annex B” of the document.

Engineering, Maintenance & Safety
In recent years, the wind industry has expanded at a rapid pace. These are exciting—and often chaotic— times for the electrical construction contractor and the new generation of wind farm electrical workers. Many of these workers have never been exposed to the hazards that the wind turbine and collector system present, and most of them still have very little knowledge of the toxicity of electricity. In the last several years the wind industry has found the value of proper engineering on the front end of a project, including acceptance testing and commissioning prior to initial energizing. Additionally, many studies have shown that routine maintenance, including testing of electrical distribution equipment, has increased reliability and minimized downtime for commercial and industrial facilities; these same philosophies hold true for wind farms.

The same can be said about protecting electrical workers who operate or service energized electrical equipment, as we now can calculate that the incident energy produced by an arcing fault is proportional to its operating time. This aspect of incident energy means that proper maintenance and testing of the over-current protective devices (OCPD) is not only an operational issue, but is also a safety issue. The very nature of maintaining an operational wind farm in a remote, outdoor and often windy environment also presents unique hazards typically not found in the commercial or industrial workplace. 

Regarding Contractors
The introduction of third-party contractors to the work site is one of the biggest exposures to liability and risk for either the plant owner or the contractor. How do you ensure the use of a contractor that has the desired safety culture as well as technical depth and talent? Before any work takes place, you should qualify the company to make sure their safety goals align with yours. You should then qualify the electrical workers to ensure that they can safely perform their services for your customer and livelihood, as well as safely interact with your electrical workers.

Data Collection
Specifying the collection and delivery format of the initial technical data is a must. Quality equipment performance data is extremely vital to trend and track the electrical equipment and system performance for the long term planning for any eventual modification of testing methodologies or frequencies of maintenance to equipment throughout the electrical equipment’s extended years of service.

Conclusion
To assure the owner that his electrical assets are safe and reliable, the contracting officer should always confirm the qualifications of the testing company prior to awarding any contract. Certification requirements are placed in bid documents to protect the consumer. Nationally-recognized certification agencies and technicians with these certifications have a proven level of competency. The consumer is assured that the technician has a well-rounded knowledge of electrical testing.

All good testing and maintenance stratagems are designed to ensure the profitability of the operation.  Periodic electrical testing, vibration testing, and alignment of the drive train are time consuming operations and are sometimes difficult to perform on a regular basis. However, the cost of unplanned outages including cranes, staffing and emergency generator repairs can also dramatically affect the bottom line.  Good planning, proper testing, and clear decisions regarding the condition of the equipment will always pay off with reduced overall maintenance costs. 

From the rotor tip to the tower base, cables are located throughout the wind turbine keeping these renewable energy power generators operating at peak efficiency. From power cables, torsion cables, fiber optic conductors, and cables for monitoring and communications to medium-voltage and fiber-optic cables for connecting into the local power grid, cables are a critical component in the success of a wind farm.

The cable framework in a wind turbine generator system (WTGS) depends on various factors, which are predetermined by the tower structure and the customer. There are various types of towers and these can be classified into five categories: steel-tube towers, concrete-tube towers, wood towers, pylon towers and hybrid towers. The hybrid towers are made of steel-reinforced concrete and steel elements and can currently be constructed up to 460 ft (140 m) in height. Depending on the construction of the tower the design of the cable framework can then be suggested to support the turbine’s power generation capacity. A wind turbine produces between 1.0 and 7.6 MW, and that power needs to be brought down from the nacelle.

Copper or aluminum? How About Both.
The turbine’s power cables can be made of copper or aluminum. Each conductor material has its own group of supporters. Those that prefer copper cable feel this material has been tested over time and has proven to be safe and reliable.  Aluminum is preferred by others because it focuses on the commercial aspect of the project, i.e. aluminum is cheaper than copper.

Aluminum makes you relatively independent of the price trend, whereas copper is much more volatile. When the copper price changes the project’s management team might have to re-think their entire material calculations to stay on budget. With aluminum, they do not have to recalculate to such a large extent. In a nutshell, one can speak of cost savings of up to 40 percent for the electrical power cabling when flexible aluminum power cables are used as compared with flexible copper cables. These savings are inclusive of the fact that more aluminum is needed to match the power levels of copper cable (i.e. a larger gauge size is needed for the aluminum cable).

Cable selection should be a collaboration between the cable manufacturer and the turbine developer. These discussions should take place with the engineers during the planning phase. The ideal power cable network should come from the four different types of existing designs. Those are Class 2 copper, Class 5 copper, Class 2 aluminum, and Class 5 aluminum. In Class 2, both copper and aluminum are rigid and inflexible. The Class 5 strand structure is the flexible version. Figure 1

Copper for the Loop
Every manufacturer of electric cables and wires has their own philosophy on selecting the correct insulation and conductor material. There are suppliers that recommend aluminum for the torsion application in the WTGS cable loop. However, many cable manufacturers test their cables for up to 10,000 cycles only. Experience tells us that testing for 15,000 to 18,000 cycles gives a more accurate, long-term test result. 

Results from tests run in our turbine test tower and from past experience shows that the aluminum application doesn’t work effectively in the loop. With WTGS service lives of approximately 20 years, demands of up to 15,000 torsion cycles will be placed on the wires in this application. This part of the power cable network, from the generator through the freely suspended loop and through the tower interior wall represents genuine stress for the wires. That is why cable specialists use exclusively Class 5 copper cabling, which has a much better ability to cope with load. The ongoing movement of the torsion cables requires a non-stick surface that allows the cables to glide easily. Therefore, special, highly abrasion-proof materials are used as the insulation material for the conductor insulation and jacketing. Figure 2

In addition, through our extensive tests we have discovered that torsion cables with a braided shield, so called C-shield, is not optimal for loop cables. We have seen damages on these types of cables after 1,000 torsion cycles. These tests further showed that a D-shield is best for high endurance under consistent twisting and un-twisting conditions.

The loop cable is one of the trickiest points in the power cable network of a wind turbine and can be the Achilles heel, if the correct cable is not selected.

Aluminum for the Tower
The conventional construction method of the wind turbine is the steel tower with three to four segments. This is where the opportunity exists for the tower constructor to pre-install the power cables. During on-site assembly, the individual cables can then be connected to each other through compressed joints using approved crimping technology. During the cable connection process, up to 80 compressed joints evolve that have to be well-executed and well-insulated to guarantee long-lasting, permanent function. Connecting the wires in an entire plant in such a fashion takes two to three days and is very costly. This critical part of the power cable network has to function correctly throughout the entire lifetime of the WTGS. Figure 3

If you consider that a crane deployment when assembling wind tower carries the cost of about $66,000 per day, the installation time needs to be kept as short as possible. For plant constructors who want to reduce this expenditure to the minimum, some manufacturers provide a cabling solution where the cables after the loop can be installed in the tower ready to plug-and-play in as little as five to six hours. A Class 5 aluminum design can be flexibly pulled into the tower structure and routed in conduits through the foundation to connect to external transformers.

Connectors for Aluminum Cables
The electro-technical aspects, however, are of the utmost importance, since a cable is only as good as the connectors that secure it at each end. Cable and connection technology should be matched and tested as one system. The conductor fill factor in the cable lug or compression connector is an important aspect. Additionally, the slight vibrations in a WTGS should also not be neglected.
Previously, only a mechanical pull-out test on the cables and connection was sufficient. For a manufacturer to provide a firm statement around product reliability, the mechanical tests need to be supplemented by an electrical test. The cable manufacturer’s philosophy is to not interrupt the power cable network if at all possible. So an uninterrupted installation into the tower up to the inverter in the tower base is preferred. In practical application, that means a prefabricated aluminum line with aluminum/copper compression joints to the loop and an aluminum/copper pressure cable lug to the inverter. In keeping with the spirit of plug-and-play, the wire can be installed through the tower and up to the inverter in one piece.

Special Crimping Technology Ensures Conductivity
Standard crimp or screw technology is not recommended with a finely-stranded aluminum cable designs due to the surface of the conductor, which oxidizes more. With conventional crimping technology, the electrical values in large cross-sections would be relatively high and insufficient. That causes excessive heating of the cable lug under load. Due to the higher temperature on the wire, the temperature of the insulation material also rises. This higher stress accelerates the aging process of the line, since contacting aluminum demands the greatest attention. Figure 4

To work around this problem, cable manufacturers have developed special connection technology for finely-stranded aluminum cables. The crimp contour makes the aluminum flow, mechanically rupturing the surface of the wire and making it conductive. This means the contour penetrates deep into the stranded bundle, facilitating ideal contact between all strands even in the bundled conductors. Another connection option is a screw technology with shear bolts. Performance reliability is extremely important. To ensure that components are in compliance, it’s important for customers to make sure the connecting equipment meet certain regulations such as IEC – DIN EN 61238-1 Class A. 

Oil and High Temperatures
The gearbox up in the nacelle requires aggressive oils and grease that can damage the cables if exposed for long periods of time. In this part of the wind turbine it is therefore important to choose cables with high oil resistance. In addition, the temperatures inside the gearbox can reach 70°C (158°F). In other words, cables that can endure higher temperatures (in Helukabel’s case up to 145°C (293°F) are suitable for applications in the nacelle.

International Regulations and Approvals
Every county has its own regulations and that is something wind turbine manufacturers should consider when choosing a cable supplier. Cables with multiple international approvals (e.g. UL, CSA, FT4, CE, VDE, TC, and WTTC) can be used in wind towers no matter where in the world they are constructed.

Halogen-Free for the American and Canadian Regions
The customer can be rest assured that both conductor materials are being protected by jacket materials that do not use halogen. The use of halogen-free cables has been a staple in the European market as the regulating body would like to prevent harmful toxins from being release in the event of a fire. However, the trend for using halogen-free cables within turbines is ever increasing in the U.S. and Canada. While UL/CSA places high importance on not allowing any fire to arise in the first place, if one does breakout regulators would also like to prevent halogen’s harmful components, such as fluorine, chlorine and iodine, from being released. Additionally, halogen further contaminates the turbine when it combines with moisture, creating hydrocyanic acid. 

Last year was a banner year for wind power by virtually every measure. Globally, 2012 saw the addition of 40 GWof wind energy capacity. The United States alone accounted for nearly one-third of that, with 13.1 GW—a new record. The surge has been largely attributed to uncertainty over extension of the production tax credit and the rush to complete projects by year-end. By the time Congress finally extended the credit in January, new installations had already begun to slow and last year’s boom is not likely to be repeated. While installations in 2013 are expected to remain flat, the outlook is more optimistic for 2014, as projects initiated in the coming year reach the production stage.

Slower market demand is bound to put downward pressure on prices. Given the market’s significant tailwind, wind power original equipment manufacturers will be looking to shrink their total costs across the entire manufacturing value chain, not only to remain competitive, but to accelerate adoption of wind-powered energy generation. Indeed, if wind power is to compete with fossil fuels and grow beyond its current six percent share of the nation’s generating capacity, driving down the cost of bringing wind turbines to market—which is passed on to energy producers and ultimately to consumers—is an industry imperative.

While the total cost of a wind turbine typically represents fifty-five to seventy percent of the total cost of an installed system, the overall cost basis is trending downward and will likely continue to do so over the foreseeable future.  A key contributor to lower costs is innovation in the assembly process. Under pressure from project developers and system owners, wind turbine OEMs are achieving lower costs by shifting assembly closer to the demand site in order to minimize the soaring costs of transportation—which by some estimates can add 10 to 15 percent to the cost of a wind farm project. Bringing that number under control requires sophisticated logistics, a tightly knit supply chain and relationships with component manufacturing partners that have the geographical reach to deliver products and provide services where they are needed.

In addition, key technology advancements are playing a major role in reducing the costs of turbine engines. Refinements in design and the use of lighter materials are helping to reduce both manufacturing and operating costs of blades and towers. The trend toward longer blades and taller towers stands to improve overall turbine efficiency and performance, meaning that more energy can be extracted from the wind with fewer turbines needed.

The industry is understandably focused on the costs of more expensive elements of the wind turbine value chain—specifically turbine blades and towers.  A less obvious but increasingly compelling opportunity to take cost out of the value chain lies in the design and assembly of the system electronics. Transformer, generator, cabling, and other control systems represent between eight and twelve percent of the total cost of the system—not a huge portion at first glance, but considering the average cost of a commercial scale turbine ranging from three to four million dollars, any incremental savings could add up quickly, especially when scaled over a large installation. That said, value chain cost considerations also apply to smaller turbines for farms ranging from five hundred thousand to one million dollars apiece.  Designed properly, a system’s electronics can not only lower the cost basis of a wind turbine system, but also enable developers and turbine original equipment manufacturers to deliver a more efficient product to their customers.

Suppliers of wind turbine system electronics compete in a fragmented market. Although a healthy percentage of electronic components are outsourced today, the changing regulatory environment, mismatches in supply and demand, and the wavering financial stability of several suppliers has prompted a growing number of original equipment manufacturers to start insourcing as a counter-measure to these market dynamics. Many are finding, however, that building versus buying is an expensive proposition that ties up valuable cash and requires a skill set outside their core competency.  And, to make things worse, a lack of diversification makes them less able to adapt to changes in business conditions.

Wind turbine system developers and original equipment manufacturers can achieve better utilization of capital resources through methodical project planning. The key is to partner with manufacturers across the wind power ecosystem that do more than build components to spec, but who have the engineering expertise and market knowledge to find ways to reduce costs without compromising performance. To compete in an environment of downward cost pressure, suppliers to OEMs must be able to add value not only through design, but also through improved sourcing, supply chain management, manufacturability, testing, and certification. They must also be able to leverage significant economies of scale in procurement and manufacturing.

Original equipment manufacturers stand to benefit if they look at design and manufacturing as an integrated process. Manufacturing partners who are steeped in wind turbine technology and understand the end product should be able to design components that can be manufactured more efficiently and cost effectively. In the electronics realm, for example, that may mean figuring out how to build a wind pitch system with fewer components, shrink the electronics footprint and reduce weight without sacrificing functionality. A supplier should also be able to provide full design-for-manufacturability, which streamlines the production process, and to perform all testing required for certification before delivering the product to the original equipment manufacturer. This requires having standing relationships with certification bodies and being fully conversant in current certification requirements. Table 1

Improving the efficiency of components and of the manufacturing process are important steps in reducing costs. Equally important is eliminating slack in the supply chain. Suppliers need to be able to demonstrate efficient logistics management at every step from the sourcing of components to the delivery of finished products when and where they are needed. Effective logistics operations today are supported by sophisticated modeling tools and techniques that enable companies to optimize everything from availability of materials to sourcing locations, transit times and distances.

As assembly is moving closer to the demand site, project developers and turbine original equipment manufacturers will be increasingly reliant on manufacturers that have a meaningful presence in the regions where projects are located. This need is likely to be met by companies that have developed a global network comprised of a highly diversified and skilled workforce experienced in assembly processes that can be matched with specific product requirements.  Given that the need for wind power tend to be modulated by government incentives, the workforce at the local level needs to be flexible so that it can expand or contract based on fluctuating demand. This requires organizations with access to and knowledge of existing governmental guidelines that preside over the businesses.

As indicated in the accompanying table, supply chain management can influence the costs of turbine components rather significantly. Today’s splintered value chain adds overhead through the duplication of purchasing and planning services. When compounded by a general supply-and-demand imbalance, these inefficiencies produce excess inventory in the pipeline.  Supply chain considerations should model the entire value chain with variables that include lead times, minimum order quantities and assembly times.  The same logic can be applied on a trickle-down basis to individual suppliers across the value chain.

Materials management in the electronics realm of the wind power value chain is critical given the emphasis that customers place on the reliability requirements of the manufactured product.  Original equipment manufacturers need to pay special attention to vendor qualification and component selection.  The purchasing leverage of the supply chain partner should also be considered, as it can lower the costs of component procurement.  In today’s wind power business, it is essential for an effective supply chain partner to have the tools to model and manage the value chain around the globe and deliver the lowest landed costs.

In the effort to reduce costs across the value chain and spur wider adoption of wind energy, developers and wind turbine original equipment manufacturers must be able to count on their industry partners for creative solutions. An important precondition to any successful manufacturing partnership is the financial viability of the supplier. Developers and original equipment manufacturers need the flexibility to stretch their capital, and downstream partners in the value chain must be able to shoulder some of the financial burden and withstand extended payment terms.
Moreover, they must have the wherewithal to invest in their own infrastructures, including assembly and test equipment, new design tools, and, of course, sufficient project staff resources.  Financial stability also means demonstrating the ability to raise capital through debt financing if required.

Wind power has moved far beyond the fringes of imagination. It is proven, viable and increasingly popular with energy producers, municipalities, corporate customers and consumers. However, if it is to make the transformation from an “alternative” to a mainstream energy source—and deliver all the attendant benefits to the environment and to society—it must be not only technically viable, but economically as well. The challenge is not simply to seek out ever-lower bids, but for turbine original equipment manufacturers and their partners across the ecosystem to work closely together to drive innovation that will produce greater efficiencies and drive down costs. 

Across the globe, wind power generation resources continue to grow.  As an example, the United States ranks second in global wind power, with more than 13 GW of new wind power installed in 2012 to pass the 60 GW milestone for installed wind power capacity.¹ The U.S. wind base experienced 28 percent growth in 2012 and wind power was the source of more than 40 percent of all new U.S. power capacity in 2012.²  The U.S. Department of Energy has indicated that wind could supply 20 percent of the U.S. electricity by 2030—requiring some 300GW of new wind generating capacity^.3 

With this type of rapid development and deployment of new wind resources, standards become critical for supporting consistent market expectations, performance benchmarks, and fundamental design features—most importantly including safety.  While many of the incidents were minor, safety incidents involving wind turbines over a five-year period in the United Kingdom were recently reported as occurring at approximately the rate of one per day.⁴  As more wind turbines are installed, new technologies are introduced to meet market and performance objectives, and the existing turbine population ages, looking to new and evolving safety standards in the design and development phase provides many benefits in supporting a safe wind infrastructure.

International Electrotechnical Commission Standards
The International Electrotechnical Commission (IEC) has published the IEC 61400 series of standards to help establish these types of standardized expectations.  IEC 61400-1, Wind Turbines – Design Requirements, outlines minimum design requirements for wind turbines. The standard “specifies essential design requirements to ensure the engineering integrity of wind turbines. Its purpose is to provide an appropriate level of protection against damage from all hazards during the planned lifetime.”⁵  The standard is a holistic document that covers many aspects of the design, installation, and use of sophisticated electromechanical equipment, and IEC 61400-1 is supplemented by numerous parts to focus on specific design or performance aspects, or types of wind turbine equipment and installations; for example, IEC 61400-2, Wind turbines – Design requirements for small wind turbines.  However, it is notable that of over 90 pages of requirements in IEC 61400-1, approximately five focus on electrical safety of the equipment, controls and protection. In those few pages, IEC 61400-1 does identify the need to evaluate most critical aspects of a wind turbine: electrical aspects, control system functions, protection system functions and critical components.  However, as the IEC 61400 documents are written today, they do not provide detailed guidance on how to adequately evaluate these critical aspects.  Work was recently initiated to review enhancements to the specific requirements for electrical safety.

Safety Standards and Codes for the U.S. Market
In order to help support a safe deployment of wind turbine system infrastructure during this projected period of rapid and significant growth, UL has led the collaborative development of national standards addressing the safety of wind turbine systems, with a focus on the electrical safety, performance of the controls and protection systems, as well as prevention of fire within the equipment. These efforts recognize that there are some fundamental differences between the installation requirements of the IEC 60364 series and the prevailing U.S. codes such as ANSI/NFPA 70, the National Electrical Code (NEC), and differences in other important safety requirements.  As a result, two wind turbine safety standards have been developed by UL: UL 6141, Standard for Safety for Large Wind Turbine Systems, and UL 6142, Standard for Safety for Small Wind Turbine Systems.  Each of these standards have been developed through a standards technical panel comprised of equipment producers, users, technology experts, scientists, regulatory authorities, and other technical experts with an interest in these specific products.  The standards have been developed using a consensus-based approach, and at this time both standards have achieved the required support within the panels to establish consensus.  The American National Standard for safety of small wind turbines was jointly published last year by UL and the American Wind Energy Association (AWEA) as ANSI/UL 6142/AWEA 6142.  UL 6141 has reached consensus, and UL is working with the standards panel to finalize the publication as an American National Standard in the near future. 

Because these requirements will constitute the American National Standards for safety, assuring compliance with the requirements for exporters, buyers, owner/operators, and other involved parties is an important measure for demonstrating due diligence in addressing workplace and consumer safety, supporting easy equipment installation and acceptance, and establishing confidence among customers.  Based on the critical role of these standards for the U.S. market, the following overview provides significant aspects of the requirements for design and testing.

These standards focus on the safety of the wind turbine systems.  However, they do not cover mechanical or structural integrity of the wind turbine system or subassemblies, or verification that the manufacturer-defined controls and protection limits maintain the system within its safe mechanical and structural limits.  The wind turbine power, control and protection systems are evaluated only to the extent that they function within the manufacturer’s specified limits and response times. These control and protection functions are evaluated with respect to risk of electric shock and fire. It is intended that the electrical subassemblies that address power transfer control and protection functions evaluated per this document are to be coordinated with the mechanical and structural limitations specified in established performance and safety standards, such as the IEC 61400 series documents.  They focus on land-based turbines, and do not specifically cover turbines for offshore installation.

Both standards contain fundamental requirements related to wind turbine safety.  These include important safety features such as: electrical safety of the internal subassemblies; protection of internal assemblies from mechanical abuse; disconnecting means; emergency stop and manual shutdown protocols; protection from self-excitation; lightning protection; safety markings and instructions; and grid connectivity (based on a number of options that address the particular needs and conditions of the grid utility).

UL 6142/AWEA 6142 covers small wind turbines for which a user or service person cannot or is not intended to enter the turbine to operate it or perform maintenance, with rated output of 1500 V ac maximum.  The standard addresses compatibility of equipment with the installation safety requirements of the NEC.  This includes compliance with Article 694, Article 705 for Interconnected Electric Power Production Sources, as well as critical safety features such as conductor and equipment protection and grounding.

UL 6141 covers large wind turbines for which a user or service person may, or is intended to, enter the turbine to operate it or perform maintenance.  UL 6141 addresses compatibility of equipment with the installation safety requirements of ANSI/IEEE C2, the National Electrical Safety Code (NESC) and the NEC as applicable.  For the NEC, this includes compliance with critical safety features such as working space, conductor and equipment protection, grounding and Article 705 for Interconnected Electric Power Production Sources.  For large wind turbines, there are some additional requirements unique to these larger products.  These address topics including protection from flame spread within the turbine, and requirements for medium voltage equipment as applicable.

The NEC addresses safe installation of systems and equipment that are not under the exclusive control of a utility, as addressed by specific requirements in Section 90.2.  The new 2014 Edition of the NEC has just been published by the National Fire Protection Association, and it contains important new requirements for safety of wind turbine installations in Article 694, “Wind Electric Systems”.  The new edition of the NEC applies to all wind systems regardless of rating, eliminating the previous scope limitation to turbines having a rating up to 100 kW.  Another new addition requires that wind systems be listed and labeled for the application. A new revision also expands on the previous limitation for a maximum of 600V rating for wind systems for dwellings, to allow systems up to 1000 V for other applications.

Harmonization Initiatives
The publication of these standards is a milestone in supporting the safe deployment of wind turbine generating systems in the U.S. market.  However, as a global organization, UL focuses on supporting global realization of our public safety Mission and supporting our global customer base in distribution of their products.  With these objectives in mind, there are several initiatives that are either underway or may be pursued in the future.

First, UL has integrated key concepts from, or references to, IEC standards into these national standards where relevant.  This was performed with the intention of bridging the gap between the IEC standards and the prevailing requirements in applicable U.S. standards and installation codes.  For example, safety related controls system requirements are coordinated with IEC 61400 requirements, and additional requirements for the performance of the integrated equipment were added based on prevailing local issues.  This approach allows the use of relevant approaches from the IEC standards while ensuring that significant local issues are addressed in a holistic and comprehensive manner.

Additionally, UL is very active in IEC Technical Committees to support the development of the best worldwide requirements for safety and performance.  UL is participating in a leadership role in a collaborative effort in IEC TC 88 in the further development and enhancement of the IEC 61400 requirements for electrical safety.  This initiative will draw on the efforts of the standards panels that have generated the requirements of UL 6141 and UL 6142, with appropriate modifications made to reflect the global nature of the IEC 61400-1 requirements.  In the past, such efforts have been very successful in the renewable energy sector, with benefits being seen in standards work on products such as solar power and inverters.  Such efforts allow the best efficiency and outcome of the IEC standards development process, allowing balanced consideration while leveraging existing, relevant content in the development process.

In the future, harmonization of the U.S. national standards with the IEC 61400 requirements is also an option.  UL looks to international harmonization as an important consideration in supporting global product development and distribution, where the relevant industries and UL are supportive of the need for the effort.  As the wind industry continues to refine product offerings and market strategies, additional consideration will be given to the benefits of harmonization.

Summary
As the global wind infrastructure sustains rapid growth, compliance with relevant standards provide validation of design principles and establish due diligence in addressing critical attributes such as safety.  The IEC 61400 series of standards provides important information for addressing safety and performance of wind turbine systems.  Efforts to address unique issues within the U.S. market has led to development of two safety standards, UL 6141 for large wind turbines and UL 6142/AWEA 6142 for small wind turbines.  These standards, which are being published as American National Standards, contain key product safety requirements for the electrical system, electrical safety and controls system, grid connection, and related safety issues.  Evolving Code requirements are promoting safety of wind installations, in part through reliance on the evaluation of turbines to the applicable product safety standards. In the future, collaborative efforts will lead to continued exchange of best practices and opportunities for broader harmonization.  Development of these standards, and their use by the manufacturing community in design and development of wind turbine products, supports maximal safety and performance of the burgeoning wind infrastructure. 

References
1. AWEA U.S. Wind Industry Annual Market Report Year Ending 2012, American Wind Energy Association, www.awea.org. Ibid.
2. 20% Wind Energy by 2030, Increasing Wind Energy’s Contribution to U.S. Electrical Supply, December 2008; U.S. Department of Energy, Energy Efficiency and Renewable Energy, www.eere.energy.gov/windandhydro.
3. Malnick E. and Mendick R., “1,500 accidents and incidents on UK wind farms”, The Telegraph, December 11, 2011.
4. IEC Publication 61400-1, Third Edition, March 2007; International Electrotechnical Commission, Geneva Switzerland.

Normally, when asking people at trade shows if they know of fiber optic cables, I see hesitance accompanied by some shoulder shrugging, and eyes wandering, frantically trying to find the answers from my booth’s advertising banners.  When people think of fiber optics, they often associate it with the telecommunication industry, the Internet, or telephone cables.  What most people don’t know is that optical fiber’s wide range of applications extends to industrial networking, including controls systems for solar and wind power.  Industrialized fiber optics provide an effective means to transmit data in the harsh environments.  How can the wind industry benefit from using fiber optics technology?  Well, if we look back at history we can see how far fiber optics can take us.

Windmills, first developed in China and Persia, have been in use since 2000 B.C.   Used extensively in the Middle East for food production by the 11th century, they influenced merchants and crusaders to carry the idea back to Europe, primarily to the Netherlands.

The Dutch adapted a new method of the windmill and used it to drain lakes and marshes in the Rhine River Delta. In the late 19th century, this technology was brought to the New World by settlers who then pumped water to farms and ranches and later generated electricity for homes and industry.  In Europe and later in America, industrialization led a steady decline in the use of windmills. However, it also sparked the development of larger windmills in order to generate electricity. These windmills became known as wind turbines, which appeared in Denmark as early as 1890.

Early in the twentieth century, advanced scientific research and discovery led to an onslaught of development, production, and manufacturing, creating an enormous demand for electricity.  Seemingly in the blink of an eye, coal mining and crude oil production grew quickly to supply the natural resources necessary for electricity generation.  With an insatiable demand for industrial and consumer electricity, the nuclear age rose as an added source for the energy needs of the world.  In June of 1954, the first nuclear power plant began operation at Obninsk, Soviet Union.  With this event, the world of energy changed forever: generation of billions of megawatts brought power and light to the farthest reaches of economically advanced continents, and incredible cities’ infrastructures emerged around these powerful electrical stations.  Centralized power generation, once a rarity, has become ubiquitous, often taken for granted as we switch on lights, charge smartphones, and enjoy the comfort of environmentally conditioned buildings. Figure 1

This energy boom, unfortunately, also introduces hazards for the population.  All too often, we witness scaled tragedies in far-away places as evidenced by refinery explosions, oil spills, and rare but far-reaching nuclear accidents.  Names like Chernobyl, Fukushima, and Macondo are etched into our collective memories as useful reminders that all forms of energy generation have inherent risk.

Seeking clean and environmentally friendly ways to produce electricity, many turn their attention to modernized wind power and other renewable energy sources.  “Wind energy became the number one source of new U.S. electricity-generating capacity for the first time in 2012, providing 42% of all new generating capacity.” In 2011, German chancellor Angela Merkel proposed a plan to replace all of German nuclear power plants by 2022 and triple the renewables share by 2050.  While these goals are ambitious, the larger picture presents a new era of innovation in alternative approaches to the energy generation.  Figure 2

Why fiber optic technology in the wind power industry?  The simple answer is that the combination of safety, efficiency, cost effectiveness, and reliable performance in harsh conditions makes fiber very attractive for use in these applications.  Fiber optic cable gear is commonly used in Supervisory Control and Data Acquisition (SCADA) systems within and between wind towers.  All dielectric fiber optic cables offer the added advantage of reducing ground potential to help protect critically important controls equipment in the event of lightning strikes.  Complex wind farms are commonly operated through fiber optic cables and switches to connect various servers to the turbines for monitoring and control of wind power plants.  Daily, millions of meters of these cables provide seamless wind farm communications and data integration from the wind towers through centralized control networks.

Known for its ability to transmit vast amounts of data over great distances, optical fiber products also offer these distinct advantages in the harsh environments of wind turbines and wind farms:

• Immunity to Radiofrequency Interference (RFI)
• Electromagnetic Interference (EMI) electrical isolation between the turbine and its controls
• Stable performance of wide operating temperature range
• Repeaterless links of several kilometers
• Simplified field connectorization with advanced cable and connector solutions

A rapid advancement of Industrial Ethernet to the wind power networks communications led to the rapid changes in the enterprise automation world and the introduction of a different breed of communications cables.  Fast (100 Mb/sec) and Gigabit Ethernet (1000Mb/sec) data rates created demand for higher bandwidth, real- time communications.  Previously widespread plastic optical fiber (POF) and copper cables could not provide these capabilities over the long distances required.  Harsh and unpredictable wind farms weather conditions required an extra layer of protection for data communication transmission. Figure 3

Graded-Index Polymer Clad Fiber (GI PCF) cables with Low Smoke Zero Halogen (LSZH) outer jackets were specifically designed for applications that require high mechanical reliability at the fiber level.  Polymer Clad Fiber not only offers a robust mechanical protection to a fiber core but also adds the important field termination capabilities to the product offering a reliable cable connectorization solution.

Naturally, power generation, transmission, and distribution create strong electrical noise.  Because using optical fiber inside wind turbines offers immunity to radiofrequency interference (RFI) in addition to electromagnetic Interference (EMI), data transmission is not affected by electrical noise. 
If optical fiber cable is the best choice, what prevents some manufacturers from using more of it in wind power applications?  Is field termination too difficult? Are technicians too hesitant to work with the fiber?

These questions present serious obstacles in choosing optical fiber; the reality is that some cable technicians are hesitant to work with glass fiber.  Some of the common misconceptions about optical fiber include that it is, “Too complicated, too fragile, too tiny to terminate, messy epoxies are used, tedious polishing processes are needed,” and my personal favorite, “you need special training and certification to work with it.” 

Historically, a common fear of the handling and long-term reliability of using glass optical fiber in such environments has hampered its adoption in wind power applications.  Through decades of development, companies like OFS have developed and proven the robustness and simplicity of using optical fibers in applications from subsea, to aerospace, medicine, factory automation, and oil and gas markets.  Recently, significant inroads have been made to both improve fiber handling and simplify field connectorization.  Today, companies like OFS, with GiHCS® optical fiber cables, and Panduit offer a Graded Index Polymer Clad Fiber (GI PCF) fiber solution along with LSZH (Low Smoke Zero Halogen) cables and LC field-installable connectors interoperable with commonly used SFP modular transceivers on their switch lines for Fast and Gigabit Ethernet Uplinks and switch ports.

Such optical fiber cable solutions help ensure stable performance in:
• widely fluctuating temperatures from -20 to +105˚C (-4 to + 221˚F)
• high vibration
• exposure to common industrial oils and chemicals
• exposure to severe electrical noise
• situations where time for connector training is minimal
• installations where technicians are not expert in fiber optics

Maintenance and onsite cable repair in harsh, exposed conditions present other big issues for some installers.  In offshore applications where wind is stronger, towers are taller with larger wind turbines and longer blades than their onshore counterparts.  Recognizing these problems, fiber optic engineers have now designed and developed a simple crimp and cleave termination system that allows for connectorization of ruggedized fiber optic cable with no need for epoxies or polishing and simplified termination training.  Climbing the tower to repair or replace a data link is simplified with lightweight fiber optic cables and compact fiber optic tool kits that require no power during connector attachment.  Following the instruction manual is extremely important; not only does it save technicians effort to “crimp it right” the first time, with no consumables, the system also increases the number of terminations they can perform with one single kit. Figure 4

The simple steps for the field termination of optical fiber breakout cables involve:  first, stripping the waterblocked outer jacket material; then, crimping the connector either directly onto the fiber optic coating (LC, SC, ST and SMA type) or  ETFE-based buffer material (V-pin and F07-type connectors), depending on the connector, for strong, solid connector retention. Strong connector to cable retention is crucial for connectorization in a turbine where strong mechanical vibration is a concern.  The third step is to create an optical finish on the fiber, using the special precision cleave tool with a diamond blade.  This crucial, but simple step creates a near perfect optical surface for low connector insertion loss.  The cleaving step eliminates the tedious need to polish the fiber end-face.  No messy adhesives or polishing equipment needed, your connectorized cable is ready to transmit at Fast and Gigabit Ethernet data rates.

At trade shows, we perform hundreds of connector termination demonstrations.  To prove the simplicity of this termination system, we ask our uninitiated customers to try the stystem for themselves through our “Crimpe, Cleave and Leave” competition.  Contestants are timed while they terminate fibers and often achieve times under 40 seconds per connector.

With only four or five steps depending on connector type, field technicians can perform thousands of terminations using tools they are familiar with.  Finally, a stress-free fiber optic zone, the holy grail of data communications, if you will.

Curiosity and genuine interest about fiber optics kept people in our booth longer and in just a few minutes, many change their perceptions toward optical fiber use in just a few minutes, following these new and simple steps.  No more shoulders shrugging or eyes wandering, previous hesitation and doubtfulness are swept away.  Our hope is that all of our contestants remember the benefits of fiber in the wind applications industry, the simplicity of learning and using the cable termination process, and the fun they had with our “Crimp, Cleave, and Leave” contest. 

In the early stages of our lives, we learn new things by exploring, studying, and trying them; each new skill with its own learning curve.  Similarly, adoption of renewable energy has its own learning curve and will take time, but the benefits for humankind are real. Windmills—basically unchanged in design for many centuries—have evolved into wind turbines, which now harness and transform the power of wind. This is made possible through technological advancements like simplified fiber optics, which contribute to a wind turbine’s safety, control, and efficiency.  We felt those winds of change, the change of people’s perceptions, and the change of their vision as they learned new things and new technologies. 

References
1. Wind Energy Foundation, “Interesting Wind Energy Facts,” Wind Energy Foundation, http://www.windenergyfoundation.org/interesting-wind-energy-facts (accessed 24 July 2013)
2. The Wind Coalition, “History of Wind Energy,” The Wind Coalition: Developing the Nation’s Wind Corridor, http://windcoalition.org/wind-energy/history-of-wind-energy/ (accessed 24 July 2013)
3. Wind Energy Foundation, “Interesting Wind Energy Facts”