Vattenfall depends on TESSA® MR fleet monitoring in the Boxberg power plant

The impressive machine transformers with up to 1100 MVA are also monitored by the fleet monitoring system.
The impressive machine transformers with up to 1100 MVA are also monitored by the fleet monitoring system.

The Boxberg coal power plant in Upper Lusatia (Saxony) is among Germany's largest power plants, with a total output of 2,575 megawatts and a power supply of approx. 20 billion kWh/year. Comprehensive monitoring of ten power transformers with up to 1100 MVA has recently begun using the TESSA® fleet monitoring system from Maschinenfabrik Reinhausen (MR) in order to achieve maximum reliability and efficiency with the longest service life.

The Boxberg power plant makes a substantial contribution to ensuring the basic power supply in Germany. Up to 6 million households can be supplied with the power that is produced. That makes it all the more important to provide the best possible protection for the transformers through the use of suitable systems. The responsible persons at Vattenfall recognized this need and responded accordingly. Specialists used their field experience to define the criteria and requirements for the monitoring system and introduced a comprehensive and thorough selection process. "We decided in favor of the TESSA® fleet monitoring system from MR because it provides an excellent platform for displaying the signals and information from the modular monitoring systems," explains Michael Lukas, Senior Expert in Transformers at Vattenfall.

Now there are ten transformers—primarily with tap changers—completely connected to the TESSA® monitoring system. All of the data and signals are centrally displayed via an intelligent platform. This includes the temperature behavior of the transformers including cooling, the crucial area of oil analysis (DGA) as well as all of the operating parameters for the transformer and the on-load tap-changer, which are determined by TAPGUARD®. The bushings are also integrated into the monitoring process and are monitored for partial discharge, capacity and the loss factor tanδ. Monitoring also provides important information about transient processes in the grid that have a large impact on transmission systems such as power transformers.

"Before TESSA®, it took a great amount of effort involving laborious information collection to learn the status of the transformers. Now we've achieved a very high level of monitoring and can obtain an excellent overview of our transformers at any time," explains Mr. Lukas. In addition, the platform provides the option of defining dependencies. For example, how does the cooling system behave when the power increases? How can optimization be achieved for maintaining a reasonable temperature level? Or how do the gas values in certain load scenarios of the transformer behave? Can any abnormalities be observed? "We have already been able to implement a lot of aspects that optimize the operating status of the transformer."

In addition, the TESSA® system provides the option of displaying additional values and information from the power plant's control system. Thus it is also possible to display and graphically illustrate relationships between energy production and transmission—for example, performance of the generator and power transformer under load.

In practice, it was a challenge to connect the transformers to TESSA® because various systems and components had to be integrated into one existing system. This was achieved with customized solutions resulting from a cooperative partnership between Vattenfall and MR. The existing components and sensors on the transformers for sending messages and signals were used and specifically upgraded with state-of-the-art communication systems for data transmission. This prevented unnecessary costs. Separate control cabinets and other equipment were also installed on the transformer as needed using an ISM® (integrated smart module), which operates as a field device to collect a wide variety of signals and centrally forward them to TESSA®. All of the various control system protocols, such as IEC61850, IEC607870-5-104 or OPC DA, were connected. "It was absolutely worth the effort and shows the performance capacity of fleet monitoring, which enables connection of a wide variety of components and information with extensive and flexible processing of protocols," states Mr. Lukas.
There are numerous benefits to having a central monitoring system. First, all essential and important information for the plant's orientation and maintenance are available in ONE place. The status of all transformers, the latest measured values and error messages as well as trends and statistics calculated from these items and, of course, maintenance recommendations—all at a glance. The goals of a fleet monitoring system are an optimized operating status of the transformers, a knowledge-based maintenance strategy and maximum reliability and efficiency with a lengthened service life. Another important aspect is a significantly improved configuration of new transformers as a result of observing the history of and evaluating the existing devices, which can be done in even greater detail thanks to knowledge gained from the monitoring system.

"The end result is optimum management of operations. Through more knowledge we are able to plan events better, increase the service life of the transformers and gain an even better understanding of dependencies," says Mr. Lukas. "In addition, we are better able to plan downtimes, and the monitoring system gives us a solid basis for deciding when we have to act and when we don't. This helps us to reduce unplanned outages, which are associated with very high costs." The economic justification of the monitoring system has already been established at the Boxberg location. Therefore the goal for the future is also clearly defined—plans call for integrating all of the transformers at the Boxberg location into TESSA®.

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