It is informally accepted by many industry players that XLPE HVAC cable systems can dynamically operate beyond the 90C normal operation limit at some points along the cable for a set period of time. Short term operation at higher temperatures is allowed for defined periods in certain regions, for example under US and Japanese standards. These periods are often limited to 72 hours, which historically suited transmission systems, but is too limiting for offshore wind. There is also a lack of clarity on how any new thermal capability can be qualified.   

The OWA Cables working group (“the OWA TWG-C”) would like to: 

• Review the physical response of the XLPE insulation system under temperatures above 90C.
• Define the actual performance increase needed in order to actualise value in real projects.  
• Identify the risk factors that need to be investigated in development/qualification tests.
• Assess the need for qualifying accessories (if not in thermally limiting locations).  
• Produce a harmonised qualification protocol for qualification of cable for Dynamic Operation beyond the Normal Operation Temperature Limit.  

The scope is limited to dry-design cables at export voltages. Anything involving water tree retardant materials for wet designs is secondary. Further, the scope includes subsea joints (both factory joints and field joints) but does not focus on end-terminations as these are locations where conductor temperature should likely not need to increase beyond current limits.  

Key experience 

• Polymer (insulation) science/chemistry
• Qualification frameworks
• Subsea cable systems  

All clarification questions and tender submissions should be sent electronically, by their respective deadlines to karolina.zieba@carbontrust.com with bethany.white@carbontrust.com in copy.

The deadline to receive clarification questions is 25 July 2025. 

The questions and answers will be posted in the ‘Tender Documents’ section below by 1 August 2025 16:00pm (BST).