IN Brief:
- A modular 400kV temporary cable system will maintain transmission capacity during substation construction and reconfiguration.
- Pluggable components allow the installation to be disconnected, stored, inspected, and deployed on later projects.
- A common specification developed by German transmission operators could support wider standardisation of temporary high-voltage connections.
NKT has delivered a reusable 400kV high-voltage alternating-current cable system for German transmission operator Amprion, providing a temporary connection that can be deployed repeatedly during substation construction and grid reconfiguration.
Designed to maintain power flows when sections of extra-high-voltage infrastructure are removed from their normal operating configuration, the modular system can be disconnected, stored, transported, and reassembled at another location. Conventional temporary installations are often engineered for a single project, leaving much of their equipment with limited value once the original works are complete.
Pluggable cable sections and associated high-voltage accessories form a complete temporary circuit, while the equipment must retain the electrical performance expected at 400kV through repeated installation, testing, removal, handling, and storage. Connector integrity, insulation coordination, mechanical protection, and consistent commissioning procedures consequently form a central part of the design.
Developed and qualified with Amprion, the system follows a technical specification established jointly by Germany’s four transmission system operators. A common specification allows temporary equipment to move more readily between projects, rather than remaining tied to one network company, substation arrangement, or installation contractor.
Amprion intends to use the cable during upgrades and reconfiguration across its extra-high-voltage estate. Temporary circuits allow construction teams to isolate existing bays, busbars, transformers, or cable terminations without leaving the affected transmission route at reduced capacity for the full duration of the works.
Temporary equipment becomes a network asset
Substation renewal is increasingly being carried out on heavily utilised networks with little tolerance for extended outages. Replacement programmes frequently proceed in stages, with old and new equipment operating alongside each other while protection schemes, control systems, and primary plant are transferred between successive configurations.
By creating an alternative path through the site, a reusable circuit gives planners more flexibility when sequencing that work. Switching, protection changes, testing, and final energisation will still require controlled interventions, although the period during which a route operates with restricted capacity or reduced redundancy can be shortened.
Repeated use also changes the commercial treatment of temporary high-voltage equipment. Where a project-specific installation is largely absorbed as a single construction cost, a reusable system can be held as a fleet asset and its cost distributed across several reinforcement programmes. Condition assessment, asset records, storage conditions, transport protection, and inspection between deployments then become part of its life-cycle management.
Standardisation will determine how efficiently that model can operate. Common connector arrangements, cable lengths, test requirements, handling procedures, and interface specifications would allow equipment to be transferred without extensive redesign, while manufacturers and installation contractors would gain a clearer basis for developing compatible accessories, jointing methods, and specialist tooling.
European transmission operators are investing heavily in substations, interconnectors, offshore connections, and inland reinforcement, much of it within existing compounds where operational equipment must remain energised. Temporary cable routes must therefore satisfy electrical-clearance, induced-voltage, earthing, fire-separation, mechanical-loading, and construction-access requirements within constrained sites.
NKT has been expanding its manufacturing base alongside the growth in high-voltage cable demand. Its recent Danish production expansion added capacity for medium- and high-voltage products, supporting a market in which both permanent infrastructure and specialist installation equipment face rising demand.
Operational experience from Amprion’s first deployments will establish how quickly the equipment can be recovered, inspected, and recommissioned at another site. Cable condition, connector performance, testing requirements, storage arrangements, and compatibility with different substation layouts will all influence the practical interval between projects.
Temporary systems cannot replace permanent reinforcement, but they can preserve network capability while that reinforcement is constructed. As transmission programmes become larger and more closely sequenced, reusable 400kV equipment offers a way to reduce repeated engineering work and extract greater value from assets that have traditionally served only one construction programme.
