Lightning-strike database spots trends, aids analysis

 

Vaisala has launched its Thunderstorm Total Lightning Database TLD100 and TLD200. These storage modules in the Vaisala Thunderstorm Information System archive cloud-to-cloud and cloud-to-ground lightning data. The TLD100/200 offers fast data collection, retrieval, and secure storage of processed lightning solutions for clients of the lightning detection system. The database is said to let lightning-network owners and lightning-data users reduce life cycle costs for lightning-data storage while also benefiting from increased performance and maintainability.

Operators use the TLD100/200 to archive lightning data into a relational database. It provides secured access to real-time lightning data, and long-term storage of stroke and flash data for post-storm and multi-year statistical analyses. It supports multiple workstations and simultaneous queries, and manages multiple user connections. The database uses the LINUX operating system and PostgreSQL relational database.

The databases are also the foundation for an optional Fault Analysis and Lightning Location System or FALLS server software, which lets users perform GIS-based data analysis, including lightning trend and density investigations against valued assets. The company has also launched FALLS  Server 5.1 and enhanced client software. The software lets utilities and wind farm operators determine whether or not lightning has affected an asset. Users can analyze events and access historical lightning data for near-real time and past occurrences. The software lets customers work proactively in an approach to determining damage caused by lightning.

“The software lets electric utility engineers and wind-farm operators easily correlate a lightning event with damaged property, obtain statistics concerning the number of lightning events or magnitudes, and evaluate lightning challenges to transmission lines, turbine blades or even an area of land for input into the design and maintenance of their systems,” says Vaisala Product Manager Steven Rowley. “Improvements to the TLD100/200 provide lightning data from 1989 to present, provide a more powerful relational database for collecting and analyzing groups of data.
Vaisala
www.vaisala.com

Handling lightning on a North Dakota wind farm

North Dakota’s flat plains and strong, steady winds make it ideal for wind farms. But this part of the country is especially susceptible to extreme weather conditions. Summer brings the threat of lightning strikes to the 300-foot tall turbines and brutally cold temperatures are commonplace in winter.

The Langdon Wind Energy Center operates a 133-turbine facility owned by NextEra Energy Resources and capable of producing 199.5 MW. To ensure the turbines operate at peak-efficiency, a team of 12 technicians perform routine maintenance duties and are on-call 24/7 in case of an emergency.

“In addition to lightning risks, we don’t send out crews if it’s colder than -28°C,” says Bill Campbell, plant leader for Langdon Wind Energy Center. “In cases of extreme cold, we only send out crews when absolutely necessary.”

To help navigate its weather challenges, the Wind Energy Center subscribes to MxVision WeatherSentry Online Wind Energy Edition professional package. Its services come from IT company Telvent. By accessing an internet-based platform, the Center stays on top of changing weather conditions that endanger operations.

For a complete view of approaching severe weather, the Center monitors radar and tracks storms, wind, and lightning on one centralized online dashboard. It features a weather map with layers that let personnel look at the specific weather information most important to its operations. This includes National Weather Service (NWS) warnings, watches, and advisories. Another layer includes custom areas of maximum impact based on parameters set by the Center to reflect how weather is affecting the exact location of its turbines.

In addition to the online dashboard, the Center uses a mobile alerting system to view current and future conditions. To stay one step ahead of the weather, employees also have access to all of the online dashboard’s weather information on their mobile phones. Additionally, personalized alerts are sent instantly to employees’ phones when severe weather nears user-defined alerting parameters. This is especially important for field technicians performing maintenance tasks.

“We let the technicians know when lightning has been detected within 60 miles,” said Campbell. “When lightning is detected within 30 miles, we require crews to evacuate the turbines.”

The mobile alerts are fed from an alert manager that provides instant notification of significant weather changes within their coverage area. When weather conditions, such as wind-speed changes or when the NWS issues a watch, warning, or advisory, an audible alarm goes off through the online dashboard. “The system alerts us by sounding a siren letting us know we must either monitor weather conditions more closely or evacuate crews,” says Campbell.

The most critical weather component for the Center is the Lightning Manager. Receiving advanced warning of real-time lightning strikes from real-time lightning data is much safer than predictions that can lead to false alarms or delayed reporting after lightning has already struck.

Five Langdon crew members use the system. They can access weather data in the office, on the wind farm, and at their homes. “If my guys get called in over a weekend, I can log on from home to find out what’s going on with the weather and ensure their safety,” says Campbell

In addition to watching storms as they pass through the area, Campbell and his technicians use hourly and 10-day forecasts to schedule routine maintenance. This allows for more efficient planning. For example, a wind turbine should not be slated for cleaning with a rain storm impending.

Although this type of renewable energy relies on the wind to generate electricity, too much wind can also impact operations and safety. If winds are too strong, crews cannot work on the turbine’s hub. Although each turbine has a wind speed indicator, Langdon Wind Energy Center also relies on Telvent for wind speed and direction to ensure optimal safety.

As a result of implementing an advanced weather information service, Campbell and his technicians have been able to improve operational efficiencies while ensuring the highest level of safety. “Safety is a shared value at our company,” said Campbell. “We rely heavily on the real-time weather information to keep our technicians safe and operations running efficiently.”

An alternative to copper-based grounding

Michael Mattera, Consultant, Bridgeport, Conn. commscope.com

Wind turbine towers are a natural target for lightning strikes. A good grounding system plays a critical role guarding against catastrophic damage to the blades, electronics, transformer, nacelle, and collector system out to the substation. Up until now, copper has been the predominant material in wire and cable used in the grounding of all manner of electrical systems. But the cost of copper fluctuates substantially and now regularly flirts with its all time high price reached back in mid 2008. This is not good news for wind-farm developers, and electrical and construction contractors who are under increasing pressure to control costs on these projects.

Smart grounding

Given the cost sensitivity of any new wind-farm project in this environment, the idea of burying a precious metal underground makes no economic sense when less expensive, proven alternatives are readily available. Fortunately, CCS has been around for decades and is a practical option to consider in grounding applications. It offers a smart alternative to copper by combining the strength of steel with the conductivity of copper through a cladding process that delivers comparable performance and a long-term return on the investment.

Safety and regulatory

The first question one might ask is: What am I giving up by choosing CCS? Frankly, the answer is: Not much other than cost. CCS delivers the needed performance when lightning strikes. To demonstrate the effectiveness of CCS in lightning protection for wind turbines, CommScope had its product tested by an independent lab in Denmark in accordance with two proposed IEC standards:

• IEC 62305-1: Protection against lightning – Part 1: General principles, and

• IEC 61400-24 Ed. 1.0: Wind Turbines – Part 24: Lightning protection CDV

These standards, scheduled for release later this year and early next year establish general principles for lightning protection as well as define specific acceptable thresholds for wind turbines. The results of these tests clearly showed that the CCS exceeded the levels called for by IEC standards.

Reliability, durability, and flexibility

In addition to performance, CCS has the advantage of longevity, reliability, and durability that any project planner would appreciate. With steel at its core, for strength, and a durable, proven cladding process, CCS also provides the performance of copper by carrying the current along the outer skin (skin affect). This combination performs optimally when needed and is easier to work with than anticipated. In addition, CCS can be connected by any exothermic welding or compression connectors in common use today ensuring full capability and direct replacement to copper in grounding applications.

Electrical comparisons to solid copper

(Click on the table below to view larger image)

Companies making CCS provide the data that lets contractors make proper electrical comparisons to copper wire. Often 4/0 copper has been used in collector systems between turbines and out to the ground grid in the substations. Understanding the actual “fault currents” within the line and system lets designers select a CCS size appropriate to the fault current instead of just using the expensive yet commonly used 4/0 stranded copper. For example, some designers have reduced the size of the CCS conductor from 4/0 copper and saved even more on the ground conductor by “right sizing” the cable to the ground faults. Fusing-current tables below help decide which size CCS to use based on electrical performance and not just physical size.

A final word: Cost

The reference above to “right sizing” means matching CCS to the equivalent physical size of copper. Because of the slightly different properties, users can choose to replace copper with a smaller sized CCS cable that still has the electrical properties to handle the fault current in a grounding application. On a direct physical size comparison, CCS is less expensive than copper, hence, users can tally additional cost savings by going with a smaller size.

With the performance of CCS established through independent testing for lightning protection, the last detail becomes under-standing the cost issue. When looking at what’s happened to the price of copper over the past year, the cost argument is an easy one to make. With the price of all precious metals rising and becoming increasingly unstable, developers, project managers, contractors, and suppliers are nervous about the impact on the cost of their next project. While pricing does fluctuate, CCS savings can average 10% or more when compared to copper. This goes to the bottom line of any project. With copper pricing showing no signs of falling back to 2009 levels anytime soon, this is good news for those who have already taken advantages of CCS. WPE

(Click on the chart below for a larger version)