Electrical power considerations for subsea systems are typically quite different from terrestrial installations. Maintenance of the plant is far more difficult and costly, so high reliability is of paramount importance. Power is invariably transmitted using Direct Current rather than Alternating Current, due to the high losses when AC is used. This introduces challenges due to the difficulty of interrupting DC and dealing with the resultant voltage surges.
Mallin Consultants have experience with engineering and implementing a wide range of underwater cable systems, including the following:
· Unrepeatered telecommunications cables
· Repeatered telecommunications cables up to 10,000 volts
· Hybrid power/fibre-optic telecommunications cables for subsea instrumentation, at voltages from 12V to 400V and power capacity up to 5kW.
The scope of Mallin Consultants’ involvement in the abovementioned systems has included route engineering, design and specification of cables, oversight of equipment manufacturer and integration, testing and managing the deployment.
The instruments and equipment installed on the seabed are exposed to a wide range of hazards that are of minor consequence on terrestrial systems. The equipment must be able to withstand extremes of pressure and require minimal maintenance. It is not unusual for the deployment of an instrument on the seabed to cost an order of magnitude more than the cost of the instrument itself, so it is essential that all reasonable measures are taken to minimise maintenance and the risk of failure of the instrument.
Terrestrial equipment generally has its housing electrically grounded, for safety reasons. However, in general, subsea equipment should be electrically isolated from seawater to prevent leakage currents that would dramatically increase corrosion rates. Mallin Consultants have in-depth knowledge and experience managing ground fault prevention, detection and mitigation.
With their extensive experience on ocean observatory deployment and operations, Mallin Consultants are uniquely qualified to address many of the electrical issues related to subsea installations.