Offshore Wind Subsea Cable Repair Joints
The already substantial offshore wind sector will experience unprecedented growth over the next decade. This will mean ever increasing quantities of installed subsea array and export power cables. Inevitably subsea cable faults will arise within this network from a variety of causes both during the challenging installation phase of OWF construction, and subsequently during the operational life of the wind farm. As offshore wind develops into a major proportion of the energy mix it will be critically important that a responsive and rapid subsea cable fault repair resource is in place. With this backdrop PCSL has developed a range of repair joints for both OWF array and export subsea power cables.
Key features of Power CSL’s repair joint range
Range taking design
The design is modular in nature allowing the jointing of cables from different manufacturers and of different designs and sizes. This creates a highly flexible repair solution (eg)
- Spare cable from one OWF can be used for repair of cables on another OWF, allowing ‘pooling’ of spare cable between an operator’s fleet of projects
- The operator can hold one size of spare cable (typically of the largest conductor size) and use this for repair of all cable sizes on a particular OWF. This mitigates the number of spare cables required as strategic stock at the OWF construction phase
- A centralised pool of standard repair joints can be held by the operator to cover all of their OWF assets. This avoids the need to hold and maintain a large number of repair joints each specific to the original cable manufacturer, and typically cable size specific. This O+M pool can be built up gradually as repair joints sourced as a contingency for each OWF’s installation and can be moved into the centralised strategic stock if not required during the construction phase.
The PCSL design also considers the wide range of optical cable types within the subsea cables and provides configurable bonding/earthing connections at the optical joint to avoid potential AC corrosion issues that may arise when connecting different types of OF cable.
The offshore installation time required for a repair joint not only impacts upon vessel on station time, but also weather window waiting time which can run to many weeks during winter months if a longer installation window is required.
PCSL has streamlined all elements of the repair joint assembly such that overall installation time is significantly shorter than many other RJ products on the market. This can yield a major reduction in repair vessel time and cost.
Repair Joint Qualification Testing
During development all PCSL repair joint products are subject to rigorous testing regimes
- Mechanical testing to CIGRE recommendations
- Electrical type test to IEC standards
- Hyperbaric testing (RWP to CIGRE recommendations)
Test programmes are subject to third party surveillance by accredited agencies. Project specific tests may also be carried out at Client’s request.
The comprehensive test programmes carried out by PCSL provide full confidence in the suitability of the products for repair operations.
Repair Joint Product Familiarisation Courses
PCSL offer repair joint assembly familiarisation courses to customers or third party power jointers, optical fibre technicians, and offshore supervisors. The courses involve the build of a complete repair joint and subsequent electrical testing of the phase joints to confirm build quality.
By this approach :
- Technicians are provided with a safe environment to acquire and practice the assembly skills required such that when they mobilise offshore they are thoroughly prepared for the joint installation
- Technicians are not relying purely on first sight of a written instruction and an expectation to learn ‘on the job’. This not only improves quality but also speed of installation
- A growing pool of technicians are available in the event of a cable repair being required
Management of Repair Joint Kits
Repair joints contain resins and components which have a defined shelf-life. It is often the case that when an OWF operator has need of a joint from their parts warehouse it is found that a number of the components within the kit are out of shelf-life, and the operator is then faced with a delivery lead-time to replenish these, impacting upon responsiveness to the cable fault.
PCSL maintain a database of all shelf-life components within repair joints supplied and this is monitored on a regular basis.
For MV and HV array cable repair joints held in Clients’ stock warehouse PCSL offer an alert service whereby the nominated representative is advised of components nearing shelf-life limit and if requested an offer for replacement components is provided.
For HV and EHV repair joints PCSL can offer an option for storage and component replenishment on an annual agreement basis.
Both approaches ensure that when needed the repair joints are immediately ready for use.