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E.ON’s First SF6-Free HEKA M Substations

How we re-engineered internal space to accommodate larger, eco-friendly equipment and completed full Internal Arc type-testing in record time, requiring minimal customer involvement.

Reference details:

Location: 

Sweden

Timeline: 

Initiated and delivered in 2025

Client: 

E.ON Sweden

Scope of work: 

Development, manufacturing, and turnkey logistics for an eco-friendly sheet metal compact substation (HEKA M).

Technical Specification:

  • Model: HEKA M CSS: HEKA1VM315-8
  • Power Capacity: Up to 315 kVA
  • Internal Arc Classification (IAC): 14 kA / 1 s
  • Enclosure Class: K15
  • Medium-Voltage Switchgear: Up to 4 bays, completely SF6-free RMU.

Challenge

Squeezing Bulkier Green Tech Into Fixed Enclosures

New environmental regulations required E.ON to expand its local grid using exclusively SF6-free (greenhouse gas-free) equipment for new consumer connection points up to 315 kVA.

However, eco-friendly medium-voltage switchgear (RMU) naturally requires significantly more physical space than traditional equipment. E.ON faced the complex challenge of adopting these greener, bulkier components quickly without increasing the footprint of the substation or derailing their expansion timeline with heavy logistical coordination.

Solution

Re-Engineered Internal Layout and Certified Safety

We re-engineered an existing compact substation model into a highly optimised sheet metal design-the HEKA M. Our engineering team completely re-imagined the internal layout to fit the larger SF6-free RMU, a 315 kVA transformer, and an integrated low-voltage solution into a single, compact enclosure.

To validate safety under the new layout, we successfully ran full Internal Arc type-testing. Furthermore, Harju Elekter assumed full ownership of the supply chain, coordinating the arrival of customer-supplied materials and managing all final transport logistics.

Result

A Certified, Plug-and-Play Launch for E.ON’s Expansion

By taking total responsibility for both the spatial redesign and the logistical coordination, Harju Elekter saved the client considerable time and administrative effort. This turnkey delivery allowed E.ON to focus entirely on grid deployment rather than project management, ensuring a sustainable and highly reliable network expansion.