Complete renovation of the Niederurnen substation in the Canton of Glarus

Axpo is constructing a modern substation in Niederurnen in the Canton of Glarus and replacing the line connections. With these measures, Axpo is making a significant contribution to the secure and sustainable supply of electricity in the Glarus region as well as in the neighbouring areas in the Canton of St. Gallen. 

In brief:

• With the construction of the new substation, Axpo is investing in a safe, sustainable and reliable energy future.
• Axpo is also increasing the operating voltage of its plants from 50 to 110 kilovolts in its grid area. As a result, all components including line connections will be converted. The voltage conversion will more than double the performance of the grid.
• When planning and implementing the project, Axpo sets great store by innovative, cost-effective and sustainable solutions.

The substation’s plants are part of the interregional distribution grid of Axpo. Here, the voltage of the electrical energy is transformed from 50 to 16 kilovolts (kV) and transferred via the grid to the local distribution network operators in the municipality of Glarus North and the neighbouring areas in the Canton of St. Gallen. The substation was built in the 1970s. The system components have now reached the end of their technical life and need to be replaced. In addition, the substation will be converted to 110 kV operation to increase the voltage from 50 to 110 kV.

A new 110 kV open-air switchgear, a new 16 kV indoor switchgear in a new building as well as new transformers are being built on the site. The building permit for the new substation became effective in 2025. Construction work will start in spring 2026 and will take around three years.

Sustainable construction

When planning the plant and selecting the components, Axpo paid particular attention to ensuring efficient and sustainable construction throughout the entire life cycle of the plants. For example, a new wooden building will be constructed and the standardised modules (containers) used for the control technology will be revised and reused at the end of their life. There are several advantages to the system concept. It optimises investment and operating costs, enables safe conversion and complies with all necessary safety standards.

Line connection

The substation is supplied with energy via the existing 13.1 km long supply line from the Grynau substation in Uznach (Canton of St. Gallen). The cable line will be converted from 50 to 110 kilovolts for operation, and will be laid underground from Schänis (mast 93) to the substation. Once the voltage conversion project has been completed in the Glarus region, the existing high-voltage overhead line in the Niederurnen substation area will be dismantled.

In addition, the Niederurnen substation will be connected via a new 110 kV underground cable line around 1.5 km long, originating from the existing Grynau-Löntsch line.

Notes for editors

Substations perform key tasks within the electricity supply system. The Niederurnen substation serves as a junction point for connecting several cable lines and forms an interface between the interregional and regional cable line levels. The electrical energy is converted from the high-voltage level (110 kV) to the medium-voltage level (16 kV) using transformers. The switchgears control and interrupt current flows: They connect and disconnect cable lines, divert electricity and protect the grid from overloads and short circuits, which is essential for grid stability and security. A distinction is made between open-air switchgears, where air serves as the insulator, and gas-insulated indoor systems. Substations form the interface between electricity generation and consumption and are therefore key to the security of the energy supply.