Prefabricated modular substations: Findings from ongoing pilot project

Today, ageing assets and increased demand for electric power, has renewed the interest for further substation development. The current challenges are extensive reinvestment needs, long substation project time spans and shortages of skilled personnel.

A pre-study estimated that the DSO will need to invest or reinvest in approx. 400 substations for 24-46/xx kV until 2045. Historically, these substations were built on-site with outdoor, airinsulated switchgear. The development of 46 kV metal-enclosed, air insulated switchgear paved the way for indoor substations with more compact designs. These were concrete constructions built on-site. Project-specific procurement led to resource-intensive and costly designs, with insufficient standardization. Consequently, the DSO is now questioning if current substation designs and working methods are too expensive or inefficient for future large-scale investments.

Prefabricated modular substations have emerged as a promising technical solution. Our hypothesis is that the DSO’s need for 24-46/xx kV substations can be fulfilled by a modular concept with four characteristics:

• Prefabrication: Substations are produced and (to a large extent) tested at the factory • Mobility: Substation modules are transported to site • Flexibility: Substation modules can be assembled in different configurations Confidentiality: C1 - Public • Business sense: The business model supports vendor competition, standardized design and generational updates Thus, the DSO launched a pilot project for 24-46/xx kV prefabricated modular substations. The primary objective is to verify that prefabricated modular substations can improve cost, time and resource efficiency, making them suitable for large-scale implementation. The pilot includes modular designs, standardized interfaces and coordination between civil works and electrical installations. To assess the need for DSO involvement in modular substation design, two approaches were adopted:

• A Market-Based Design (Vendor Option), which employs technical solutions and layouts available from suppliers • A Standard Interface Design (Standard Interface) based on the DSO’s layout and standardized interfaces The development pilot commenced with the procurement of two Vendor Option 46/12 kV substation projects. The suppliers have been contracted, and these substations are due for commissioning in 2026. Following, two Standard Interface 46/12 kV substations will be procured. Technical, economic and business model aspects are evaluated during the pilot project.

This paper presents technical requirements, vendor feedback, and early pilot results.

Preliminary findings indicate that a cost reduction by 20 % is viable. The findings also note that the market is receptive to prefabricated modular substations. No technical showstoppers have been identified, and lead-time reductions have been indicated. So far, the modular concept shows promise for long-term scalability and improved resource efficiency.

Finally, the paper presents a detailed account of findings to date and assess their implications for large-scale implementation of prefabricated modular substations.