Offshore renewables: a framework for subsea power cable safety

Responding to this trend, new technical guidance from ABS aims to close the gap between existing subsea cable standards and the reliability requirements of rapidly expanding offshore renewable infrastructure, writes ABS vice president global offshore renewables Rob Langford.

The subsea sector is booming, with deepwater and ultra-deepwater oil and gas developments set to drive spending between 2024 and 2027 north of US$42Bn. Boom times, however, bring challenges. Industry surveys indicate that rising costs and supply chain constraints are among the most significant obstacles facing subsea development, cited by around 40% of executives, while analysts at Rystad Energy point to capacity constraints building through 2026 and intensifying in 2027. These constraints will only bite deeper as offshore renewables and carbon capture projects, both of which are set to play a significant role in the future energy mix, add to the subsea backlog. 

This is a technically demanding segment, with subsea projects facing harsh metocean and environmental loads against a backdrop of increasing regulatory complexity, underscoring the need for objective technical guidance to help operators with compliance and safety goals. This is a tall order, especially considering the need to support the innovation required for offshore electrification – be it oil, solar, wave and wind projects, or even floating data centres and nuclear power plants. It is against this clear need that ABS has developed its new Technical Standard for Subsea Power Cables.

The guidance is published at a time when subsea power cables are in high demand to support a dynamic and increasingly diverse energy mix. Rapid growth in offshore wind, emerging offshore data centres, cross-border interconnectors, and the electrification of offshore oil and gas assets are expected to significantly increase global demand for subsea power cables. 

It is not just that more offshore assets require subsea electrification, the assets themselves – be they turbines, substations or ultra-deep oil developments – require higher voltage and are located at further distances and deeper depths than ever before. In practical terms, this means more cables, greater transmission capacity and more demanding engineering requirements across the entire cable lifecycle – from design and manufacturing to installation, operation and maintenance.

Despite their critical role, subsea power cables remain one of the most vulnerable components of offshore energy infrastructure, with cable failure cited as a primary source of financial loss in offshore wind. A top cause of offshore wind insurance claims and financial losses is subsea cable failures, according to industry analysts, highlighting the need for stronger design, installation, and operational controls. 

These studies show that subsea cable failures most frequently stem from installation damage, including over-bending, improper handling and inadequate seabed interface protection. Other failure mechanisms include anchor strikes, severe weather loads exceeding design limits, insufficient burial depth, and violations of minimum bending radius requirements.

Addressing these risks requires a lifecycle approach that considers cable integrity from initial design through installation, commissioning and long-term operation.

The challenges associated with subsea power cables become even more pronounced in floating offshore wind developments. When it comes to offshore wind, subsea power cables perform two essential functions: inter-array cables connect individual floating turbines and an offshore substation, while export cables carry the aggregated power from that substation back to shore and into the grid. Without a reliable cable infrastructure, a floating windfarm simply cannot deliver energy. 

In conventional fixed-bottom windfarms, export and inter-array cables are typically laid along the seabed and remain largely static throughout their operational life. Floating windfarms, by contrast, introduce dynamic motion.

Floating turbines – and in some cases floating substations – are moored to the seabed but continuously move in response to wind, wave and current forces. As a result, the sections of cable suspended in the water column must be designed as dynamic cables capable of accommodating constant motion.

These dynamic cables, typically configured in a ‘lazy wave’ shape using distributed buoyancy modules, must maintain electrical performance while enduring millions of fatigue loading cycles. Ensuring the long-term reliability of these systems requires careful attention to fatigue performance, bending limits, mechanical protection and installation procedures.

Subsea power cables are the backbone of offshore transmission systems and need to be designed, installed and maintained to the highest standards to support the long-term performance and reliability of critical energy infrastructure. Yet the subsea cable itself remains a frontier where standards, certification and design accountability are still catching up with the pace of deployment. ABS’s Technical Standard for Subsea Power Cables was developed to help address this gap.