Most economic way to move 1 MW across a river

[ruxton.stanislaw]

My team is considering options for the most cost effective way to move ~1 MW of energy across a river in subterranean cable, with an approximate total distance of 1 km (0.62 miles). The origin is a 800Y/461.5 V transformer from the utility. It will be rectified for use and that can occur before or after the long haul. We can also use medium voltage. However, with safety the number one priority, a concern is damage to the cable and leakage current. We are thinking to use delta-wye transformers and run the drain/neutrals of the cables through a CT with a ground fault relay to disconnect the main contactors in the event of a fault.

 

[synchro]

Okonite MV submarine cable with its inner layer of galvanized steel wire armor would be suitable for this application. I don't know what it costs, but I'm sure it will be substantial.

https://www.okonite.com/media/catalog/product/files/2-30.pdf

 

[electrofelon]

That submarine cable is sweet, would love to know how much it costs. To me the tricky part is the engineering of the physical aspects of the installation. Can the cable just lay on the river bed ? Are current and sediment movement an issue? What will those forces do to the cable?

 

[petersonra]

1 mw at 800 volts is about 720 amps. A km of that is a lot of voltage drop.

I would think mv is likely more cost effective.

 

[ggunn]

Microwaves?

 

[Jraef]

1 mw at 800 volts is about 720 amps. A km of that is a lot of voltage drop.

I would think mv is likely more cost effective.

I agree. Costly yes, but solves other problems too, such as the shear weight of that LV cable and the pulling force necessary to go that far. You are probably talking about parallel 750kcmils for a LV run, but would probably be looking at a single 1/0 cable, MAYBE 2/0, if you used 4160V (shooting from the hip on those sizes just for comparison purposes).

 

[petersonra]

There is a submerged cable crossing a local river. It might be a km long. There are a bunch of signs banning anchoring of boats in the area. I think it just lays on the riverbed.

 

[electrofelon]

I agree. Costly yes, but solves other problems too, such as the shear weight of that LV cable and the pulling force necessary to go that far. You are probably talking about parallel 750kcmils for a LV run, but would probably be looking at a single 1/0 cable, MAYBE 2/0, if you used 4160V (shooting from the hip on those sizes just for comparison purposes).

For 12.47kv looks like only #6 is required!

 

[ruxton.stanislaw]

For 12.47kv looks like only #6 is required!

I think that's the direction we are going in. High grade medium voltage submarine cable, but the saving grace is the smaller conductor size. There is going to be a scary cage in the back room of the building that no one will want to go into.

Thanks guys!

 

[Jraef]

For 12.47kv looks like only #6 is required!

Yes, but the 15kV class switchgear will be a lot more expensive.

 

[electrofelon]

Yes, but the 15kV class switchgear will be a lot more expensive.

With a step up step down, if one uses padmount transformers, they have fusing built in which can be configured to
Meet transformer and secondary conductors protection so no switchgear is needed.