An Integrated Approach to Assessing Emergency Anchoring Risks to Subsea Power Cables

De-risking offshore wind

Company / Unternehmen: Intertek
Speaker / Referent: Saijie Sim

Subsea power cables connect high value assets to the electrical grid, and damage can lead to high financial losses. A major risk to cables is the emergency anchoring of vessels. Anchor dropping or dragging on a cable will normally lead to cable failure. Several methods exist to calculate the probabilities of cable failure, however they generally have shortcomings in navigationally constrained areas where risks may be highest. This presentation proposes an integrated approach taking into account the events leading to anchoring, such as vessel tracks, stopping distances and anchor penetration in different soils, to come up with a more robust and accurate assessment of the anchoring risk. The use of probability assessments is becoming increasingly popular amongst marine insurers and cable owners to assess the risks to the cable, with premiums often relying on the calculated probabilities of failure. This is carried out to ensure that all efforts have been taken to reduce the risks to as low as reasonably practical.
The presentation will explain the current approaches used and highlight some of their limitations. A new integrated approach will then be proposed that takes into account the following aspects to provide a more accurate and robust assessment of the anchoring risk:

– A risk based method which takes into account the key stages in the events leading up to emergency anchoring.
– A method for factoring the effects of change in shipping intensity in proximity of the cable e.g. near shipping lanes, confined areas, etc.

A new probability formula is derived based on the above events to assess the cable failure from emergency anchoring. A case study and results will be presented to demonstrate the outcome of the formula and reinforce the accuracy and robustness of the integrated approach