Case Study
North Sea Link

UMD and DC System secure operation of a 132kW motor drive during power outage and disturbances


The North Sea Link (NSL) is the longest subsea cable in the world that will enable a bi-directional flow of renewable electricity between the UK and Norway. Construction on the project commenced in March 2015 and the new interconnector was scheduled to be online in 2021.

The NSL project involves the installation of 720km of subsea cables, 10km of onshore cables and the construction of converter stations at both ends.


The onshore converter stations for the North Sea Link will handling the AC to DC and vice versa to feed the national grids. The converter process generates undesirable heat which require continuous cooling to avoid overheating in the converters. A water-cooling pump system is installed to cool the converters during operation. If a power outage is occurring during operation the pump system needs a seamless power backup. By using KraftPowercon UMD™ system the critical power infrastructure is secured for continuously operation.


Scope of supply to converter station in Kvilldal and Blyth

220V battery system including 230V AC output (or UPS)
The DC system is designed to provide uninterrupted power to control system and all other DC supplied equipment in the converter station. Provides flexibility by adjusting the output power, easy maintenance by hot swap and high availability with parallel modules. Monitoring of the batteries, rectifier and distribution, status, and alarms distinctly on display, settings via clear menus for easy handling.

Uninterruptible Motor Drive system for cooling pumps

HVAC Electricity
1. Blyth 400kV Substation
2. Converter Station & Underground Cable

HVDC Electricity
3. Subsea Cable

HVAC Electricity
4. Converter Station & Underground Cable
5. Kvilldal 420kV Substation


Electrical configuration for each station:
220V DC system, in total consisting of:

  • 220V DC charger with main distribution cabinet
  • 220V DC batteries (1000Ah)
  • DC distributions
  • 230V AC UPS Inverter system (16kVA)


  • Pre-engineered and factory tested
  • Fulfilling specification and local
    legislation in Norway & UK

Uninterruptible power for motor drive

Electrical configuration for each station:

  • Two (2) UMD™ S400

UMD™ S400 is an inverter system for uninterruptible operation of a standard AC-motor with mains supply and with back-up from a battery system. The transition from mains supply to battery supply is automatic and seamless.

Each UMD™ Feeding: One (1) Cooling pump (>100kW each) with one (1) cooling pump in standby


  • Standardized, type tested concept for converter cooling
  • Highest possible availability
  • Eliminates Single Point of Failure

With decades of experiences KraftPowercon provides solutions for Uninterruptible Motor Drives. In the North Sea Link project we have customized the solution to meet the high expectations and demands.

Håkan Rydenborg - Technical Sales Manager, KraftPowercon

Case Study North Sea Link