Grid connection up to 150 kV – HV cable design and sizing

Drawing on our experience with cables, NIRAS helps create robust connections across the grid, from 0.4 kV low voltage to 150 kV high voltage. As a multidisciplinary consultancy, we can take on the full project from initial concept to final commissioning. Below is a selection of our services and capabilities for grid connection up to 150 kV, including cable connections, cable sizing and cable installations.

Services and capabilities for grid connection and cable installations

Network analysis and cable sizing

We carry out advanced grid calculations, including load flow and short-circuit analysis, to determine the optimal cable cross-section and the right cable type. This ensures that cables have the necessary capacity for both current and future loads, while maintaining power quality and stability. Through simulations we can, for example, assess the impact of large new electricity consumers or generators on the grid and size cables accordingly.

Planning and regulatory approvals

We support high-level feasibility studies and the planning of cable projects, including assessing whether existing overhead lines could be replaced with underground cables. For new cable connections, a thorough and accurate route survey is critical for project quality, cost and feasibility. We use drones as an efficient and low-impact tool in the early-stage analysis. We manage the dialogue with network operators and authorities on grid connection, technical network requirements and permits, so the project moves safely through every approval stage.

Detailed design and calculations

NIRAS carries out the detailed electrical design of the cable installation. We select the right cable types (for example XLPE-insulated cables), size the conductor cross-section correctly and plan optimal routing (direct buried, ducted and other configurations) with regard to the environment and surroundings. At the same time, we prepare technical specifications for all components, from cable joints and terminations to protection relays, in line with applicable standards and best practice. The aim is an optimal design that meets the client's needs and all safety requirements, including for cable-based grid connection.

Tendering, site management and installation

We prepare complete tender documents and technical specifications for cable contracts and support the evaluation of bids and selection of the right suppliers. During installation, we act as project manager and specialist supervisor to ensure quality of execution. Our experienced engineers monitor that cables are installed correctly in line with project specifications and schedule. This rigorous project management and cross-discipline coordination ensures the installation is delivered on time and to the highest quality.

Testing and commissioning

Once the cables are installed, we plan and monitor the final tests of the installation. We support the commissioning itself and verify that the new cable installation performs as expected under both normal operation and fault scenarios. Through documented test procedures, we ensure all requirements from the client and the network operator are met, so the cables can be placed into service with full confidence.

Typical project flow: from feasibility study to commissioning

A cable project from initial concept to commissioning typically follows five steps:

1. Feasibility study and concept

Initial techno-economic analysis of needs and options. We map the grid's capacity and assess alternative solutions. The aim is to define the overall project concept and confirm that the project is feasible.

2. Detailed design and engineering

Detailed planning of the cable installation, including sizing of cables and components and the preparation of technical drawings and specifications. We define the optimal cable routes and select the right cable types and cross-sections, where relevant supported by drone surveys as an efficient, low-impact tool. All design choices are aligned with applicable standards and reflect both technical requirements and local conditions.

3. Grid connection and regulatory approvals

Dialogue with the network operator and relevant authorities to secure grid connection up to 150 kV and obtain all necessary permits. We prepare applications and documentation demonstrating that the new cable installation meets technical network requirements. Through close engagement with authorities, we ensure the project obtains the required approvals without unnecessary delays.

4. Tendering and installation

Preparation of tender documents and technical specifications for procurement of cables, equipment and contractor work. NIRAS supports the gathering and evaluation of bids and the selection of the best suppliers. When the project enters the construction phase, we take on project management and specialist supervision during cable installation to ensure the work is carried out to plan and at high quality.

5. Testing and commissioning

Once the cable installation is complete, we support the final tests prior to commissioning. We plan and coordinate the commissioning phase, where the cable route is thoroughly tested, including electrical tests on the cables and verification that all protection systems function correctly.

What does grid connection up to 150 kV at NIRAS cover?

Grid connection up to 150 kV can include planning, technical documentation and delivery of cable projects, including network analysis, cable sizing, dialogue with the network operator and authorities, as well as testing and commissioning.

Which analyses do you use for grid connection?

We carry out advanced grid calculations, including load flow and short-circuit analysis, to support the correct sizing and documentation of the cable installation.

How do you approach cable sizing and selection of cable type?

We size the conductor cross-section and select the right cable type based on loads, operating scenarios and technical requirements. The aim is a design that supports capacity, power quality and stability.

Can you help with regulatory processes and dialogue with the network operator?

Yes. We manage the dialogue with network operators and authorities on grid connection, technical network requirements and permits, so the project moves safely through the necessary approval stages.

What does testing and commissioning of a cable installation involve?

We plan and monitor the final tests and support commissioning, where the cable route is tested and protection systems are checked to ensure they function correctly, so the requirements from the client and the network operator are met.