Nexans to invest €1 billion in increased High Voltage DC Cables Technology and Capacity

NKT plans to build a new plant, including a third extrusion tower in Karlskrona, Sweden, as well as a new market-leading power cable vessel. These investments are driven by growing demand for high-voltage DC cables, a strong order book, and a record backlog of more than €7 billion at the end of the first quarter of 2023.


Since March 2023, NKT has confirmed more than €5 billion in high-voltage contract awards and booking commitments. To realize this significant order book, prepare for a continued strong market outlook, and execute on the record high backlog, NKT will invest approximately €1 billion in its high-voltage power cable business.

These investments include a new market-leading vessel with record power cable laying capacity compared to vessels in the existing world fleet and a major expansion of the Swedish production site in Karlskrona.

Here, NKT will build a new plant, including a third 200-meter extrusion tower, adding end-to-end production capacity alongside the existing facility. This will make the plant the world’s largest production site for high-voltage offshore cables.


Nexans’ Response

Claes Westerlind, President and CEO of Nexans (NKT), said: “The orders and commitments awarded by our customers in recent months underscore our efforts in integrated solutions, XLPE, and leadership in high-voltage DC technology. Power cables are a key element in the transition to renewable energy, and current high voltage production and installation capacity is insufficient to meet the growing market demand. We are pleased to continue to grow NKT in line with our strategic ambitions and to continue to develop our turnkey power cable offering to our customers.”

Submarine cable work
Submarine cable work


Advantages of High Voltage DC Cables

HVDC transmission has the following main advantages over high-voltage AC transmission:

1 Lower cost of DC lines when the transmission power is the same

Three-phase AC power needs three wires to transmit, each wire to ground insulation to be designed under its peak value of two times the effective value, while DC power only needs two wires (if a single pole only one) and DC peak value is equal to the effective value.

Therefore, DC transmission can save a lot of transmission materials, and also reduce a lot of transportation and installation costs.

Secondly, the overhead line tower structure of DC transmission is simpler, the line corridor is narrower, and the cable with the same insulation level can run at a higher voltage.

2 High Voltage DC Transmission Power Consumption is Small

Because DC overhead lines use only 1 or 2 wires, the active loss is small.

And it also has a “space charge” effect, it’s corona loss and radio interference are smaller than the AC overhead lines.

3 Suitable for Submarine Power Transmission

General AC power transmission is mostly overhead, the line and the earth form a capacitance, but because the composition of the air capacitance is very small, the impact on the circuit transmission is very small.

But for underground cables and submarine cables, because the cable and the land between the sea will form a larger capacitance. Therefore, the capacitive resistance is smaller than that of overhead installation, which is equivalent to the formation of additional branches, which in turn causes additional line losses.

4 The Problem of Reactive Angle Stability

In an AC transmission system, all synchronous generators connected to the power system must be kept in synchronous operation.

If a DC line is used to connect two AC systems, the above stability problems do not exist because the DC line has no reactance, which means that DC transmission is not limited by the transmission distance.

5 Can Limit the Short-Circuit Current of the System

When connecting two AC systems with AC transmission lines, the short-circuit current will increase due to the increase in system capacity. It is possible to exceed the original circuit breaker interrupting capacity, which requires the replacement of numerous pieces of equipment, increasing the amount of investment. In DC transmission, there is no such problem.

6 Adjustment Speed Fast and Reliable Operation

DC transmission through the thyristor converter can easily and quickly adjust the active power and realize the tide flip.

If a bipolar line is used, when one pole fails, the other pole can still use earth or water as a circuit to continue to transmit half of the power, which also improves the reliability of operation.

Subsea cable
Subsea cable

The main future research content of high-voltage DC cables

The main properties of DC cable insulation materials include electrical conductivity, thermal conductivity, mechanical and space charge properties, and environmental friendliness.

How to regulate the various properties of cable insulation materials is a long-standing challenge for scholars at home and abroad to solve.

The development of extruded DC cables needs to solve two key scientific problems: the generation, transport, accumulation, and dissipation processes of medium space surface charges under the action of multi-field coupling and the synergistic regulation of insulation medium multi-properties.


Based on the above information, it is sufficient to show that the development of high-voltage DC cables is necessary.

Nexans also points out that from 2023 to 2026, these investments regarding high-voltage DC are expected to reach about 1 billion euros.

They will increase NKT’s capacity to meet the growing demand for especially long-distance HVDC power cable solutions, thus significantly strengthening NKT’s market leadership.

The new assets will be commissioned in 2027.

In 2020, NKT launched its investment program for the high-voltage plant, driven by a record backlog of orders, including for the German corridor project, and a positive market outlook.

A key part of the program is the addition of a second extrusion tower for the Swedish plant in Karlskrona, which has now been completed.

The additional investment was announced in 2022 following continued positive market development.

Driven by the previous investment program, more than 300 new employees have joined the Karlskrona plant since 2020.

Now, NKT expects the Swedish plant to welcome more than 500 new employees in 2027 following the investment.


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