The plan to run large ships on a medium voltage DC network has passed its second test with ABS. The classification society has recognised HD Korea Shipbuilding & Offshore Engineering (HD KSOE) and HD Hyundai Heavy Industries (HHI) for completing the Concept Verification stage of its New Technology Qualification (NTQ) programme for a breakerless medium voltage direct current (MVDC) power system.
ABS announced the milestone on 26 October 2026. The system is rated at around 30 MW and is designed for large commercial vessels that need high power distribution on board.
At a glance
Breakerless MVDC power systemDevelopersHD KSOE and HD Hyundai Heavy IndustriesClassificationABS, New Technology Qualification programmeRatingAround 30 MWTarget vesselsLarge commercial ships with high power demandBasisHD Hyundai's modular propulsion drive systemJoint development projectStarted 2024Feasibility stageCompleted 2025Concept VerificationCompleted, announced 26 October 2026Next stagePrototype Validation
What the system does
Most large electric ships today distribute power as alternating current. An MVDC network distributes it as direct current at medium voltage instead, which lets generators, batteries, fuel cells and propulsion drives connect to one DC bus through power electronics. HD Hyundai has said that on large electric propulsion ships MVDC can improve the efficiency of integrating these energy sources by up to 20% compared with conventional AC systems.
The hard part with DC is protection. A DC fault current has no natural zero crossing, so the large DC circuit breakers needed to interrupt it at medium voltage are bulky and costly. A breakerless architecture handles faults through the system's controls and converters rather than relying on those breakers. ABS says the HD Hyundai design uses advanced controls and fault management to deliver safe and resilient power distribution, and that it is meant to help owners improve energy efficiency and support high capacity electrification as ships get bigger.
How it got here
- May 2024: ABS, HD KSOE and HHI agreed to develop an MVDC transmission and distribution system for electric propulsion ships and to work on international standards for marine MVDC, which did not yet exist
- August 2025: ABS issued an NTQ certificate for the breakerless MVDC power system, the first of its kind; HD KSOE said it covered both commercial and naval vessels
- October 2026: Concept Verification completed
- Next: Prototype Validation, with the partners also working on new ABS requirements for high voltage DC systems and a new ABS notation
Low voltage DC systems are already covered by ABS's Requirements for DC Power Distribution Systems for Marine and Offshore Applications. Medium voltage rules are the gap this project is meant to fill.
Why it matters
Ships are taking on more electrical load: bigger batteries, fuel cells, shore power, and propulsion drives running from mixed energy sources. An efficient onboard DC grid makes it easier to plug those sources together, and a 30 MW rating puts the system in the range of large cargo ships rather than ferries and offshore vessels, where DC grids are already more common. For ports, more electrified ships mean more vessels able to take shore power and, in time, to charge at the quay.
Classification is often the slow step for new power systems. Moving through the NTQ stages one by one gives owners and yards a recognised path to approval before the technology reaches an order book.
More on ship and port electrification is in Electric ferries and vessel charging and Shore power and OPS.
DC is moving up from ferries to big ships. Prototype Validation will show whether a 30 MW network without breakers holds up in hardware.
