Eisackwerk-GmbH

Generator Breaker Systems for St. Anton (Italy) hydroelectric power plant
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An environmentally protected area

A hydro power plant means a challenge for power generating company in term of environment protection. To preserve the landscape as much as possible electrical systems are installed in underground caverns. TROYER AG, which is implementing the entire electromechanical equipment for the hydroelectric power plant, has decided on MV distribution systems from Siemens, as it has always been a reliable partner.

Modernization of the hydroelectric power plant

St. Anton power plant to the north of Bolzano, Italy, is already somewhat dated: Since 1951, this plant has been generating 270 million kilowatt hours (kWh) of electric energy per year; this works out to 750 to 850 megawatt hours (MWh) per day. This makes St. Anton the fifth largest hydroelectric power plant in South Tyrol; the three turbines generate up to 72 mega- watts (MW) of electric power at times. After the modification, maximum output is to increase to 90 MW and annual production to 300 million kilowatt hours. TROYER AG, which is implementing the entire electromechanical equipment for the hydroelectric power plant, has decided on MV distribution systems from Siemens, as Siemens has always been a reliable partner for Troyer in the past!

Challenge

Synchronization of the generators with the grid

St. Anton is on the edge of the city; it does not have a buffer lake at the bottom as for a pumped storage hydroelectric plant. At full load, 91.5% mechanical energy should be produced from the water pressure at the turbine and 89.9% electrical energy at the generator. Eisackwerk GmbH, which operates the power plant, is currently having it modernized. However, hardly anything can be seen of the largest hydroelectric plant in Italy; it must have a low impact on the environment: Everything that does not have to be out in the open is in underground caverns. Troyer AG's three new Pelton turbines will be operated 300 meters deep in the mountain. The new penstock supplying the high-pressure water to the turbines was sunk vertically. The water will thus flow down the longest vertical penstock in Europe. The generated electric power will then be routed out of the mountain at a medium voltage of 13. 8 kV and then transformed on the outside to an ultra-high voltage of 220,000 V for the interconnected European power grid. Commissioning is planned for the spring of 2019. This modification is a challenge, also for synchronization of the generators with the grid.

We have had many years' experience with Siemens from previous projects. It's important that we have a trustworthy partner.
Alexander Wild from Troyer AG (electrical engineering department head)

The VB1 generator switchgear system is the perfect solution for multiple connected supply systems

Siemens secured the order in this project for the delivery of four model VB1 17.5 kV generator switchgear systems (2000-5000A). "This generator switchgear system is the perfect solution for multiple connected supply systems. High switching capacity and small space requirements are needed and this provides an ideal solution," explains Siemens project manager Maike Grossner.

The system with the pressure equalizing duct

Siemens was able to provide a customized solution that met the challenges of the installation.

The flexible and compact design was a deciding factor for us: The systems could be installed in rows. Three generator switchgear systems were supplied for connecting the three synchronous generators and the fourth for switching the 120 MVA transformer to the medium-voltage level; an individual solution was developed for this plant.
Alexander Wild from Troyer AG (electrical engineering department head)

Low environmental impact

The proven and SF6-free vacuum technology of the Siemens Generator circuit-breaker 

Hydroelectric power plants such as St. Anton are needed for grid stability to compensate for the ever greater power demand and the fluctuating supply from solar and wind power. Energy distribution with a low environmental impact is also in demand: It is also important for the customer to forego the use of SF6 gas in underground installations. With its EcoTransparency products and systems, Siemens wants to create an ecological system that meets people's needs and supports customers in the optimum utilization of resources. Generator switchgear systems - as a part of Siemens' Blue Portfolio - are equipped with vacuum circuit breakers, the proven and reliable Siemens switching technology that is SF6-free and therefore requires no gas monitoring!