How can I select a suitable cable with this characteristics:

  • The cable is connected at one end to a 690 V power generator that is between 6 and 40 meter below the surface of a big river and converts the kinetic energy of the water into electricity, directedly, without a dam.
  • A step up transformer from 690 V to a higher voltage, for diminishing the losses, mounted underwater is not accepted for technical and safety reasons.
  • The max current through the cable is 550 A.
  • The cable should be able to carry a three phase AC current having a frequency of between 20 and 30 Hz.
  • The length of the cable is between 800 and 1200 meters and it ends on the bank of the river.
  • Accepted power losses in the cable are max 40 kW.
  • Preferably, the cable should carry also an optical fibre for communicating with the controller of the underwater generator.

I have found on the internet high voltage underwater cables but it appears that, not knowing where to look for with precision, the type of cable with the characteristics I enumerated above is difficult to find. Can you help me with some advices for finding such a less usual cable?

  • 3
    \$\begingroup\$ This sounds like a homework problem or someone in over their head in project that should be outsourced. An experienced person should be doing the water-tight slices let alone specifying and sourcing the cable. \$\endgroup\$ Apr 23, 2022 at 12:46
  • 2
    \$\begingroup\$ If 40kW losses are acceptable, the overall power must be quite high snd the river flowing quite fast. Fast flowing water will create an erosive environment so you can't just specify waterproof cable (specified for still water), you'll need to consider the rocks, gravel, sand and silt flowing past the cable which can be like sandpaper constantly eroding it. \$\endgroup\$ Apr 23, 2022 at 12:49
  • \$\begingroup\$ After a week or so of searching the net I was not able to find the cable with the characteristics I mentioned. Please do not discourage people to give an useful answer. This is neither a homework nor an outsourcing project. I need this cable. \$\endgroup\$ Apr 23, 2022 at 12:51
  • 1
    \$\begingroup\$ This is a very difficult application, both due to the harsh physical environment, the length, the high current and the low frequency. Your cable will be extremely expensive - so expensive, in fact, that contracting a certified electrician will have a comparable or lower cost to the parts. I have very low confidence that this problem will meet regulatory and safety standards without participation from a licensed professional. \$\endgroup\$
    – Reinderien
    Apr 23, 2022 at 15:02
  • 3
    \$\begingroup\$ If the cable is buried in the river bed, it may overheat if thermal conductivity of the bed material is too low. \$\endgroup\$
    – Uwe
    Apr 23, 2022 at 15:48

1 Answer 1


For something as out there as this you absolutely need to be talking to the applications engineers at the cable manufacturers, likely one of the specialist sub surface ones.

There should however be extensive experience in the offshore wind power industry, so I would be talking to someone like the Prysmian group or Tratos who do sub sea power (This is on the small side for them). In particular I think Tratos might be able to do you a variant on their tidal stream turbine cable that may be suitable, but all of this is very much a case of talk to a vendors applications engineering folk.

I would expect this to be a very expensive cable.

  • \$\begingroup\$ After reading your answer I sent an email to Tratos describing in detail the cable I need. If they answer I will write here what they say. \$\endgroup\$ Apr 24, 2022 at 7:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.