Continual advances are being made in the control and monitoring of subsea oil wells by the application of new technology for sensors, subsea processing and communications devices. With these advances, the demands on the subsea umbilical are constantly increasing with deployment lengths and depths growing and the quantity of controlled functions now greater than ever. The need for a good understanding of the effects of deployment subsea is essential, as communications frequencies and data throughput constantly increase. This research aims to address some of the issues regarding umbilical modelling and sets up a series of tests to measure the effects of pressure and cable flooding within the umbilical and assesses the effect of steel tubes, hydraulic hoses and cable armouring on the operating parameters of the cables. In addition, the cables are modelled using electromagnetic field solver tools and the results compared with those measured. Once prediction losses have been established, these are compared with measurements taken on the full lengths of umbilical and the reasons for any discrepancies examined. It is shown that, in a typical subsea umbilical, the proximity of conducting cores to adjacent components, such as hydraulic hoses or steel wire armour, the flooding with sea water and the pressure due to the depth of deployment all have a significant impact on the impedance parameters of the cables. The effect of cable screening on attenuation is also examined and it is shown that, as well as affecting capacitance and conductance, the screen has a significant impact on the cable resistance and inductance, with the resistance rising to a maximum at a certain screen thickness before a subsequent reduction. This effect was investigated further by modelling with an electromagnetic field solver and a possible explanation for this effect is proposed. Comparison of the modelled data and measurement of cables under the various operating conditions investigated show good correlation with the results, allowing very accurate prediction of the effects on electrical performance of cables when deployed subsea in Subsea Control System umbilicals.

The operational life of all-dielectric self supporting (ADSS) optical fibre cables installed on high voltage over-head power transmission lines is limited by sheath degradation caused by induced electrical activity on the cable's surface. The work presented in this thesis describes research completed to quantify this degradation. This has resulted in a novel analysis method being developed and used to associate product testing with field trial results. The analysis is based on evaluating the magnitude of recorded electrical activity and fitting an appropriate distribution to the data to describe relative electrical arcing power. This innovation was possible due to the completion of a comprehensive review of the theories dealing with the generation of the electrical activity, followed by a detailed analysis. Where appropriate, worked examples are given in the thesis to demonstrate these theories. As a result of this work three proposals have been made to simplify future analyses. They are: approximating the relevant variables to span related polynomial functions, relating capacitive coupling to the space potential, and the superposition of assumed functions. The work is supported by results presented of extensive practical testing and simulations carried out by the author. These include analyses of the resulting cable damage, some of which has not been discriminated between in previous work. The completed analysis of tested products has also identified, previously not quantified, degradation accelerants. The work classifies these accelerants into extrinsic installation and intrinsic product factors. The thesis presents and reviews the implication of the electrical degradation resistance of sheaths applied to slotted-core and advance multi-loose tube (MLT) optical fibre cable designs. This has lead to the evaluation of three generations of sheath technology, which varied from low smoke compound technology, through to bimodal polyethylene. The work also identifies specific methods to limit risk to products. They include the use of pre-blended materials and the need to assure both sheath surface finish quality and cable longitudinal water blocking. Finally, the thesis summarises the development of new and previously investigated proposed degradation mitigation systems. Selected possible solutions were then evaluated using tests and analysis methods developed by the author, and compared with those of other notable works. This has resulted in the filing of two patents. As a result of this research a solution has been trialed and proposed to the collaborating company. This will allow optical fibre cable to be installed in high potential fields for the prescribed lifetime, overcoming previous limitations.

Cathodic delamination failure is believed to be caused by the production of OH- at the polymer/metal interface via oxygen reduction reactions. In cable connector assemblies, the use of manufacturing processes and materials that are resistant to cathodic delamination failures is highly desirable. Also, there is a need for an accelerated testing regime for assessing the resistance of polymer-to-metal composites to cathodic delamination failures. Cable connector assemblies are employed in marine environments for structural terminations and circuit interconnection of electrical power and signal cabling systems. They are found on offshore sea beds, ROV’s, vessels and submarines and are prone to cathodic delamination related failures particularly when the cable assemblies are coupled to dissimilar metal appurtenances in seawater, e.g., zinc anodes. The resistance to cathodic delamination failures of selected metal substrates and polymeric materials used in the manufacture and sealing of cable connector assemblies have been investigated. Materials and methods of surface preparation by grit blasting to enhance polymer-to-metal adhesion, thus increasing the service life-time expectation of cable connector assemblies have been elucidated. Methods of accelerated testing of polymer/metal bond durability using salt spray test and the validation of the results in seawater immersion tests and potentiostatic experiments have been described. Also, a novel accelerated test chamber for cathodic delamination tests was designed and manufactured. Applied potential was observed to be the factor that had the most negative effect on test samples while silicon carbide grit was found to produce the most effective surface cleanliness and roughness combination required for durable polymer-to-metal bonds.