Steering hybrid switchgear down a steep gorge

2015-02-25 - Innovative high-voltage hybrid switchgear PASS (Plug and Switch System) is ensuring reliable power delivery from a difficult-to-access hydroelectric plant in northern Italy, owned by major Italian utility Edison.

The region of Lombardy sees the plains of northern Italy turn into the peaks of the Alps. It is home to the Fontanamora hydroelectric plant, which generates three megawatts (MW) of renewable power from turbines and auxiliary machinery situated by a fast-flowing river at the bottom of a steep gorge.

The plant belongs to Edison, one of Europe’s oldest power companies and a major Italian electrical utility with a strong focus on renewable generation. It has 7.7 gigawatts (GW) of installed renewable capacity, comprising hydroelectric, wind, solar, thermoelectric plants, and a biomass system.

At the beginning of 2013, Edison decided to undertake a complete revamp of the plant, with the project including also the step-up of the voltage level of connection to the electricity grid, from medium to high voltage. The customer decided to replace the previously installed switchgear with a new product featuring the latest in switching technology: ABB's PASS hybrid switchgear module, rated at 72.5 kilovolts (kV).

The project was challenging both technically and from an installation perspective, as access to the powerhouse is only possible by way of a steep, narrow stairway down the side of the gorge. Entrance to the powerhouse is small, and the room available for installing switchgear is only three square meters wide.

To cope with these difficult space challenges, ABB leveraged its expertise in switchgear design to supply a hybrid module that integrates a circuit breaker and two disconnectors, plus current and voltage transformers and the control and protection relay in a single unit. Plug-in cable terminals instead of traditional air-insulated bushings were deployed to further reduce the module's size, enabling it to fit it in the reduced space of the Fontanamora powerhouse.

To overcome the narrow stairway and minimize transport risks, the installation team secured the PASS hybrid module with special harness straps and lowered it down into the gorge with a crane. The preassembled unit arrived on site pretested for high-voltage and ready for installation, which took four days. There was no need for the additional equipment typically needed to perform on-site high-voltage tests, so the ABB PASS hybrid module could be put into service without delay, saving time and costs.

The PASS module is energized and now in service, showing the lengths, depths and heights ABB will go to for its customers – and every challenge is an opportunity.

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