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06.02.2019

Increasing efficiency and asbestos removal for an Italian hydropower plant

BENNING has performed the repair of a generator in an extremely short period of time. Modern insulation material technology increases efficiency and extends the service life of the machine.

View into the generator with the 180 newly wound high-voltage coils
View into the generator with the 180 newly wound high-voltage coils

Hydropower is one of the most important renewable energy sources in the world. While in Germany it generates about 5 percent of the electricity produced, in Italy, for example, it generates 20 percent, in Switzerland 62 percent, and in Austria as much as 76 percent. A key advantage is that water does not produce any emissions and therefore has no negative effects on the climate. It also enables relatively low-cost production of large quantities of electricity. One could ask, what more could you want? However, there remains a major need for optimisation in this energy sector, above all in terms of efficiency, reliability and sustainability.

Many facilities are outdated - having often been in operation for as long as 50 years or even more. Modernisation processes can help to increase the performance of a facility in the long term and are also often more efficient than a new build. In addition to technical retrofitting, for example by replacing hydroelectric generators, asbestos removal is also a subject of great importance. Even though this health-damaging, fine-fibre silicate mineral was banned throughout Germany back in 1993, asbestos issues often have to be resolved when repairing older electrical machines.

In addition, every new hydropower facility, irrespective of its design and technical characteristics, has an ecological impact on the surrounding environment or region. It can, for example, result in the disruption of natural river courses or the elimination of flood zones. Another reason to pursue not only the construction of new hydropower facilities, but also the modernisation and more efficient use of existing ones - an area in which BENNING's Electrical Machines (BeM) division has been successfully operating for many decades.

Reduced downtime

We recently completed the repair of a generator with a rated output of 12.3 MW for a hydropower facility in northern Italy. In this case, a generator failure had occurred as a result of a short circuit in the winding. Since a failure causes huge losses in terms of the feed-in tariff, the repair had to be performed as quickly as possible. In no time at all, the facility got in touch with BENNING, with the first contact being made at a trade fair in 2017.

Within a very short time, BENNING took over the drafting and presentation of a suitable maintenance concept. Compared to the installation of a new generator, it reduced the time substantially.Other key advantages: The use of modern insulating material technology extends the service life of the machine by decades. In addition, the nominal power can be significantly increased by means of a new winding design.

For the operator of the hydropower facility, this means greater efficiency, safety and sustainability. But this was not only the advantage of the offering. The many references to similar projects, as well as the great deadline flexibility of BENNING is what won the client over.

Graun church tower on Lake Reschensee in the South Tyrol - even the development of hydropower means disruption in the surrounding region, so it is all the more important to modernise the existing hydropower facilities and increase their efficiency.
Graun church tower on Lake Reschensee in the South Tyrol - even the development of hydropower means disruption in the surrounding region, so it is all the more important to modernise the existing hydropower facilities and increase their efficiency.

Efficient maintenance

On 24 January 2018, only six days after the offer had been submitted, repair work began on the facility. This included dismantling and cleaning on site using the dry snow process, obtaining transport permission and arranging special transport because of the stator width (external diameter: 3.8 m, height: 2 m, weight: over 30 t).

The measurements of the 4 t flat enamelled copper wire integrated in the generator were taken directly on site at the facility. This made it possible to significantly reduce the procurement time for the new wire.

The loading of the generator in the facility took place on 28 February. For the subsequent transport, the Reschenpass (AT) had to be temporarily blocked, but this did not cause any major loss of time. As early as 2 March, the equipment safely reached the repair works in Bocholt. In Bocholt, the removal of asbestos from the stator, the dismantling of the winding in the so-called black area (asbestos), the examination of the existing sheet stack for hotspots by thermography as well as the new design and production of the high-voltage winding all took place.

Maximum flexibility

In particular, the dismantling of the winding, which had to be performed very carefully due to the asbestos removal, turned out to be extremely time-consuming.

Thanks to the flexibility of the electrical machines division, however, there was no risk to the scheduled loading deadlines, nor was there any risk of the 180 high-voltage coils required for the new winding having to be manufactured.

Major client satisfaction

The thermography on the sheet metal package was performed on 18 May in the presence of the client. The tests showed the sheet stack to be in order, so that the installation of the high-voltage coils began immediately afterwards in three-shift operation.

Thanks to the additionally optimised winding design from BENNING, the nominal power of the generator was actually increased by approx. 1 MW.

The loading of the generator in the repair shop took place as scheduled on 4 July. Thus, BENNING avoided the risk that a delivery could not have taken place until 11 July due to road closures. The generator arrived without delay at the northern Italian facility on 6 July.

The client was more than satisfied with the fast and professional service, as well as increased efficiency achieved, and promised BENNING several follow-up orders for further generators.

Bottom line

Compared to a new generator build, the repair time of a generator is significantly shorter and so the downtime is also reduced.

The service life of the machine is extended by decades, through the use of modern insulating material technology and the nominal power can be increased significantly in some cases by means of a new winding design.

Sustainable factors that are both positive for our environment and in the interest of hydroelectric operators.

Further Information

contact: Matthias Lörwink
telephone: +49 2871 93-318
e-Mail: m.loerwink@benning.de

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