Power supply architecture for a 2 km tether ROV

Hello folks ,
I need some advice from most of you because i am thinking about the power architecture for a long tether ROV (1.5 - 2KM long). Actually i need to use 4 number of T500 thrusters (24V 43.5A @full throttle) and also have some low power loads like led lights , sonar,…(Anyway my load requirements is fixed to 3500-4000W)…I hope a high voltage DC transmission is better for longer lengths. Earlier we used a 370V DC transmission through tether , but the maximum possible tether length is some 300 m only!!..Can anyone suggest me some higher voltage power transmission possibility (600-700 V DC)…( I am aware of the safety concerns about High voltage transmission, But need such a deeper tether operation !!)

Are you using the stock BlueROV tether?
At those voltages, you will probably need some thicker copper. I work with an ROV at 425V with a 1700m long tether at around 4kW load.
Also, be sure you have some kind of ground fault detection in place.

I havent purchased any ROV tether yet…I used to calculate the wire gauge (Chosen 14 AWG copper conductor . current capacity = 15A)…My load is 4000W for the peak so fixing a 700V DC transmission the current can be limted to some 6 or 7 amps…

Here is an incomplete power architeture in my mind which i need to modify with you guys…

Thank you for previous response [CA_BlueBoat]

can you update me about the power conversions and SMPS used in your 1700 m long project??

We have a 240V 3 phase → 425V DC (10A I think) → 1700m tether (~25V drop on the tether) → 48V DC for thrusters

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Okay…This system is almost similar to my requirement . But is there exists only 25V drop on a 1700m long tether ! ! ! …Even if you are using a thick 10AWG (Heavy) copper conductor, for a 10A the voltage drop should be some 65V… I am asking you this , because I need to know if there is any such efficient tether manufacturer is there (You know Cable loss reduction is crucial in long tether applications)

Im fairly new to working on this vehicle and i cant remember off the top of my head. It may be 4 conductors 2 in parallel…
Im very busy the next few days but i will certainly get back to you when I can because I’m very interested too. I’ll try to find out the manufacturer, but im also certain it was in the >$100k range fyi.


Well…Thank you [CA_BlueBoat]

I found out the vehicle uses 6x 13 AWG conductors, South Bay Cable built it.
we have 425Vdc on the top and at a load of 15A the voltage at the vehicle is ~ 280V.

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