Subsea Electric Power Transmission Techniques from DC to AC

Subsea military submarine project.

In the past decade, the significant improvements in high speed, high voltage transistor technology enabled the design of more sophisticated subsea electric power transmission systems.

This is the case of the power-electronics-based single wire DC and high-frequency AC transmission systems that appeared as alternatives to the traditional three phase transmission systems.

Although such advanced alternatives have been employed on a scenario basis, no thorough study comparing these different options has been carried out. A paper co-authored by Michael Wrinch, An Analysis of Subsea Electric Power Transmission Techniques from DC to AC 50=60 Hz and Beyond, aims to examine 50/60Hz AC, DC and high frequency AC electrical transmission systems regarding their technical and financial advantages and drawbacks, through steady-state and transient analysis of a 10 km, 100kVA ROV.

This paper has compared the electrical aspects of transmitting electricity using 50/60 Hz, 400 Hz, and DC carriers. The results show that each technique has a distinctive advantage over the other while each also has drawbacks for subsea electric power. 

System comparisons

The 50/60 Hz systems contain the fewest risks with over 50 years of solid engineering development while high frequency items have lower weight (about 1/4), faster start up and greater voltage drop problems. Finally, DC systems have the largest cost savings with a reduced wire count and a potentially lower voltage drop but have the highest design and reliability risk. With all considered, there is no doubt that history is making its full circle back to the discussions of Thomas Edison and Nikola Tesla as if AC or DC systems are better. From this analysis it can be seen that they were both correct and only needed today’s technology to catch up to allow their AC/DC innovations to be combined. 

This paper has compared the electrical aspects of transmitting electricity using 50/60 Hz, 400 Hz, and DC carriers. The results show that each technique has a distinctive advantage over the other while each also has drawbacks. The 50/60 Hz systems contain the fewest risks with over 50 years of solid engineering development while high frequency items have lower weight (about 1/4), faster start up and greater voltage drop problems. Finally, DC systems have the largest cost savings with a reduced wire count and a potentially lower voltage drop but have the highest design and reliability risk. 

With all considered, there is no doubt that history is making its full circle back to the discussions of Thomas Edison and Nikola Tesla as if AC or DC systems are better. From this analysis it can be seen that they were both correct and only needed today’s technology to catch up to allow their AC/DC innovations to be combined.

More resources: http://ece.ubc.ca/event/2016/04/power-electronics-key-enabling-technology-sustainable-world

Hedgehog Technologies specializes in electrical engineering project management and systems design of high-energy control, manufacturing, smart grid and automation systems.

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