| Wind Turbine Design: Lighting & electrical service |
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Most utility or commercial grade wind turbines are constructed using these basic features: a foundation, a multi-sectional steel or concrete tube tower, a machine-head or nacelle, and a hub (a rotating frame-work with blades attached). Nowadays, hub-height elevations for this class of wind turbine are generally between 55 and 100 meters. Similar to any multi-level building type construction, wind turbine designs must contain certain service elements, as well. Lighting and electrical service outlet systems are distinctive parts included in most wind turbine tower and nacelle designs. The design focuses of these integral electrical systems are to provide safety, accessibility, and functionality during construction, operation, and maintenance periods. Lighting system designs should assure adequate illumination throughout the tower. More specifically, lighting levels in passage areas between platforms and in work areas, as well as on top of platforms, around equipment bays, and control enclosures, should all be considered. These same considerations should be given to the nacelle and hub areas, too. Power outlets for powering tools and equipment should be easily accessible in every work area and provide adequate voltage and current throughout the entire system. These facts are true no matter where wind turbines are installed on the planet. As the North American wind energy market has grown measurably over the past few years, and continues to grow, a very rich market has presented several OEM’s from outside North America with great opportunity to grow their businesses. This movement, primarily from Europe and the Asia-Pacific regions, has presented some challenges for most of these OEM’s. One challenge these companies face is designing lighting and electrical systems to meet specific electrical code and compliance requirements in North America. In many cases, the original internal electrical system designs from these pioneering wind turbine OEM’s, are now, and have been for many years, based upon requirements for installations in compliance with various approval and certifying agencies enveloping their preceding geographic markets. For example, it is clear there are differences in commonly available service power between European, Asian-Pacific, and North American wind turbine applications. In North America, the most common service power for tower internal electrical systems is 120VAC, 60 Hz. Whereas, the most common service power in Europe is 220VAC, 50 Hz, and, in the Asia-Pacific regions, it varies between 220VAC, 50Hz and 220VAC, 60Hz. Contrasting electrical design characteristics of the regions are further evident as different plug and service receptacle configurations are found. Required wire and cable sizes may also differ (metric vs. AWG), as will other electrical components and materials suitable to the varying range of supply voltage. Some electrical components and devices are only compatible with their specific regions and applications but, fortunately, there are light fixtures available that will operate on variable power inputs, satisfying the needs of many regions. Each region has different agency approval requirements that are unrelated to those required in the other regions, and they are not necessarily transferable or harmonized. In North America, Nationally Recognized Testing Laboratory (NRTL) certifications and listings for components, materials, and systems are required to meet National Electrical Codes (NEC). Some of the NRTL’s are Underwriters Laboratories (UL), Electrical Testing Laboratories (ETL), Canadian Standards Association (CSA), and Factory Mutual (FM). Although there are several other qualifying labs, these represent the most recognized in North America. In addition, there are many areas where Occupational Safety and Health Act (OSHA) and National Fire Protection Association (NFPA) guidelines and requirements need to be considered in the design and installation of the systems. Agency approval requirements have created many challenges for the European and Asian-Pacific OEM’s as they seek to evaluate and/or re-design their lighting and service power systems to meet the North American standards and requirements. The goal of this effort is to be certain that their turbines internal electrical systems will meet or exceed point of delivery electrical code compliance when installed. How do they do it? The answer is not always easy and, in fact, it can be quite complicated. It is not as simple as just changing out some electrical components and materials. Some OEM’s have found out the hard way, resulting in customer dissatisfaction, late turbine commissioning, ultimately costing them hundreds of thousands of dollars to correct. The OEM’s must determine not only which code compliant electrical components and materials they can use, but how and where they can be installed in the towers and nacelles, too. There are some significant differences between North America, Europe, and the Asia-Pacific regions in this regard and, in many cases, a complete system re-design is necessary, causing a complete change in electrical components and materials including; rerouting of cables, relocation of light fixtures, electrical outlet receptacles, and switches. These are very common occurrences with some of these OEM designs when considered for application in North America. Generally, materials and installation methods that are compliant in Europe and the Asian-Pacific regions are not compliant with the electrical codes and requirements in North America. An example of a design and installation issue observed of non-North American OEM lighting and electrical service systems is finding the power cables attached to personnel ladders. This situation has the potential to create many safety issues: the possibility of a climber damaging the cables while climbing or, worse yet, causing a climber to become tangled in cables, causing injury as a result. Also, consider the potential of electrical shock to the climber caused by contact with exposed conductors of a previously damaged cable. Another example is when electrical cables are passed through the rungs of an aluminum personnel ladder, effectively using the ladder rung as a conduit to pass cables to the other side of the tower. This cable installation method presents issues in consideration of North American electrical codes and, if a rung was to fracture and subsequently cut a cable, a short circuit could occur with varying results including the potential for personnel injury. North American electrical code compliance is violated again when light fixture or power receptacle outlet assemblies are mounted directly to personnel ladders. These assemblies, mounted in or near the personnel climbing envelope, may cause snagging or climbing interference and, if damaged, could also cause varying results including short circuits and the potential for personnel injury. Development of North American compliant design and installation requirements as discussed above need not be a concern for these OEM’s as there are a few companies in North America that specialize in assisting European and Asian-Pacific OEM’s with design conversions, or redesigns, for North American compliant lighting and electrical outlet services for their towers and nacelles. These companies provide conversion assistance based upon the OEM’s desires and can also provide engineered lighting and electrical service kits and systems designed for their specific towers and nacelles. These companies also work directly with the OEM and its tower vendors to assure code compliant and cost-effective installations, and can provide training to the field construction personnel to assure final jobsite installation compliance and conformance, as well. One such company, for instance, offers pre-engineered, pre-fabricated, pre-tested, plug & play lighting and electrical service systems that have an ETL Listing for both the US and Canada. Such a system removes the guesswork related to code compliance, and does away with the very costly hand wiring, troubleshooting, repairs, and rework typically associated with build-in-place lighting and electrical service systems. This approach saves OEM’s a great deal of time, frustration, and money, and can keep the end customer content, as there is little chance of having any electrical inspector surprises or delays at the jobsite related to installation. The differences in electrical code compliance between these regions should not be ignored nor taken lightly. Some OEM’s have done so only to have paid the price after the fact, experiencing very high rework and reinstallation costs coupled with significant project delays. Any potential issues in the OEM’s designs can be addressed by specialized companies located in North America who are postured to help. These companies have several years of experience working directly with the European and Asian-Pacific OEM’s and their tower and nacelle manufactures, providing design and engineering experience and expertise, and great knowledge of North American electrical and safety codes, and can supply lighting and electrical service kits and systems.
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North American Code Compliance