Remote Monitoring Makes Maintenance a Breeze for Wind Farms16 Feb, 2011 By: Colin Roberts
Beijing's Guohua Energy Investment Company deploys an SKF sensor system to keep tabs on turbine conditions.
When the fourth-biggest wind farm operator in China increases its installed capacity by 50% within one year, that indicates a company that knows its business. And one of the business aspects that all wind farm operators must attend to is "turbine reliability" — keeping the turbines turning as much as possible, and keeping maintenance activities down to a minimum. Reduced maintenance is always a valuable contribution to bottom-line profitability, but when you've got 2,000 MW of installed capacity, then you are talking about huge amounts of money on the line.
That is why Weihua Zhou, Deputy General Manager of the Production Department for Guohua Energy Investment Company, based in Beijing, made a decision in 2008 to evaluate his maintenance strategy and the technology to be applied within that strategy. A critical decision was to look for the fastest and most effective way to determine the health of his turbines.
Investigating Online Monitoring
With several turbine designs and sizes out in the field, Zhou needed the best possible way to get reliable and regular information about the general condition of selected turbines of these designs and types. At the same time, he wanted to identify any typical negative trends that might occur in the various field operating conditions that the turbines are exposed to.
Not satisfied with his previous assessment process of only using temperature readings of gearbox oil and generator bearing housings, Zhou wanted to investigate online monitoring, where vibration signals from critical components are collected 24 hours a day and analyzed to determine where problems are developing, and how severe they are. This type of monitoring would allow critical maintenance to be planned well in advance, helping the company avoid unexpected and very costly breakdowns. He knew that this type of condition monitoring is widely used in countries such as the United States, Europe, and Australia.
Close study of vibration spectra reveals the condition of machinery and components.
Using vibration sensors mounted on a turbine's main shaft bearings, drive train gearbox, and generator, SKF WindCon 3.0 collects, analyzes, and compiles a configurable range of operating data. WindCon uses CAN-bus interconnectivity to a number of the systems found in a modern wind turbine, such as centralized lubrication systems, blade monitoring systems, and gearbox oil condition systems. WindCon can track operating conditions such as unbalanced propeller blades, misalignment, gear damage, electrical problems, and tower vibrations.
These conditions can all be remotely monitored at maintenance centers, or on any Internet-connected computer or mobile device, through SKF WebCon analysis software. When the system indicates that maintenance activities are necessary, they can then be scheduled at the earliest opportunity, enabling optimum turbine operation and preventing potential machinery failure. Data collected with WindCon also enables root cause failure analysis to eliminate recurring failures.
Diagnostics in Action
Zhou's first step was to research what technology was available, and the quality and knowledge of the suppliers. These investigations covered all the key suppliers of such technology, but contacts with other wind farm operators in China brought him to consider SKF and its turbine monitoring system. In order to get first-hand experience of SKF's remote capabilities, Zhou visited the company's Intelligence Centre Wind (ICW), a facility in Hamburg, Germany, dedicated to wind turbine diagnostics. SKF analyze remotely collected data at the center, and when irregularities are detected, customers are notified by e-mail.
At the time of Zhou's visit, the SKF ICW was receiving and processing data from more than 600 turbines located across Europe and in the United States. The Hamburg visit spurred Zhou to set up a field trial on certain turbines in Guohua wind farms in 2009.
The field trial involved 11 SKF WindCon systems to be deployed across three wind farms: one in Jiangsu province, one in Shadong province, and one in Inner Mongolia. Around the time that SKF was installing its systems in the Guohua turbines, SKF opened a Remote Condition Monitoring Centre in Shanghai. The data was collected on a local server at each wind farm and transmitted to an SKF server in Shanghai for analysis.
Any immediate emergency situation would be reported at once, but no such problem was detected at monitoring startup, and a report was issued once per month to the wind farm site managers and Zhou himself. The reports contained the detailed vibration spectra for the key components being monitored, together with a brief statement that summarized the analysis of the data in terms of the condition of the component. There was also a report grid for the components being monitored, which used one of three colors to indicate acceptable conditions (green), a slight to major deviation from acceptable levels or trends (yellow), and a situation requiring immediate attention (red).
The first results were good; Zhou could see for the first time what was really happening with his critical machinery. The SKF WindCon systems delivered the vibration spectra, similar to those he saw in Hamburg, and the SKF experts in Shanghai interpreted the data in terms of the condition of the bearings, potential misalignment, gear damage, etc.
During the six months to January 2010, the WindCon units continued to provide information on the turbines, allowing Zhou to determine what maintenance would be required. In that period, one of the installed SKF WindCons identified a severely damaged generator gearbox bearing at the Inner Mongolia wind farm.
"The SKF WindCons did their job," said Zhou. "They kept me informed and the early identification of the severity of the damaged bearing in Inner Mongolia was enough to allow us to plan for replacement at minimum cost and disturbance to the planned electricity supply from the turbine."
Further Deployment of WindCon
Since the tests, Guohua has installed another 58 SKF WindCons, and a further 280 have been ordered for new turbines going into service in 2011. This is the start of a mass application of remote monitoring.
"We have some knowledge regarding vibration analysis within our own maintenance teams," said Zhou, "but I intend to build up more knowledge within the Guohua organization and set up our own remote monitoring centre in Beijing for our turbines. A lot of this knowledge and assistance will come from SKF as they provide us with their remote diagnostic monitoring during the coming years."
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