Project Overview
The interconnector will connect two major power grids using submarine cables. The new interconnector will better handle power loads and prevent failures. This project was initiated to solve the problem of power failure in some sections of the existing submarine cables installed in the same area.
The project confirmed Longitude’s vast knowledge in cable installation by providing installation procedures for both the shore landings and the complicated simultaneous lay and burial operation with vertical injector. The project was handled from the Singapore office by successfully transferring the knowledge from the offshore cable installation developed in Europe to the South East Asian hub.

TOWING ANALYSIS AND PROCEDURES
Longitude acted alongside the project owners, LSCS, from the very beginning of the project by determining the towing route for cable lay barge movement to site and creating the towing procedures for MWS and Client Approval.

SHORE LANDING STRUCTURES – GEOTECHNICAL ANALYSIS
Due to the complex shore approach, landing structures were designed to allow for cable spacing and alignment. Longitude carried out the geotechnical stability assessment to ensure the structures will be suitable for the installation.

SHORE PULL-IN INSTALLATION ANALYSIS AND PROCEDURES
Thanks to Longitude’s knowledge in offshore operations and cable installations an innovative second end landing was developed with the barge relocation on landing area to suite the project constraints. This was a challenging operation to plan, computationally model and determine in the procedures to ensure safety and cable integrity.

The scope included the development of cable landing approach and relevant procedures together with the development of mobilisation procedures for both sites to ensure suitable equipment is mobilised.

Complete dynamic analysis to determine forces during pull-in were carried out to determine the operation’s limits and the number and size of supports needed.

The analysis also allowed to assess the floater and determine the minimum spacing required for the operation. Cable landings rigging were also developed for over-boarding and pulling. Shore landing support structures installed on the cable ramps were developed to ensure straight landing of cables.

Industry standard software OrcaFlex was used for all installation analyses combined with automation scripts and bespoke tools developed exclusively by Longitude to guarantee the project timelines deliverables.

INSTALLATION ANALYSIS AND PROCEDURES
Due to the complex cable installation layout the analysis included the cable installation sequencing review and impact assessment. This was discussed with client and installation contractor to ensure safety of installation.

Deck layouts and equipment was reviewed based on operational and analysis requirements.

The barge used a 4-point mooring system with thrusters’ support. Longitude developed a full skidding mooring plan for operation and both shore landings. This was also revised further to initial anchor handling trials.

Pre-set anchors design and discussion with components suppliers were held due to the lack of soil holding capacity near one of the shore ends.

The analysis included also the development and analysis of mooring floating catenary design to avoid several subsea obstacles.
Complex mooring operations procedures including thruster assisted mooring with the use of two thrusters.
Analysis and procedures for simultaneous lay and burial of several power cables using vertical injector were also carried out.
Cable abandonment and recovery procedures.
Development of storyboards for all the operation including landings and installation.
HAZID and HAZOP participation for all operation.
Planning meetings with client to determine schedule of operation and concurrent operations.