They are installing an underground electrical cable in my neighborhood. It
has about 20 plastic tubes 4 inches in diameter. I suppose they will have
metal conductors inside. Does anybody know about this design? I suppose it
is about 750kv. What if water gets inside to tube?
Why do you think it is power cables?
Why do you think it is ~750kV? 20 lots of 750kV is rather a lot of power...
It will help cool the cable. Plastic tubes of the ribbed variety often
are just push fit into each other and laid on a sand base. No attempt is
made to keep water out and they often have small slots in them anyhow,
to stop gas build up, etc.. Nice wet ground will take the heat away
better and will probably give the cable a longer life.
If it is power cable, then, you are right, it will have metal conductors
inside. But the metal conductors will be covered in insulating material
and then have stranded steel armour around that, then another layer of
insulation. The tube is covered with sand and a strip of bright yellow
warning tape laid over that. Electricity distribution companies are
rather keen that the electric stays in the pipe.
I think it is electric power because the electric power company said that's
what it is. They say it will deliver about 3 megawatts to a major medical
area here -- about 15 hospitals and several research establishments.
I can assure you that it is not anywhere near 750KV for that kind of load.
That kind of voltage is used for carrying huge amounts of power over vast
distances. Power for whole cities. I'd guess the voltage for that load is
30KV or less.
Bill Browning schrieb:
cables for 750 kV have a nominal current of about 700 A, that is 525 MW.
A cable with 30 kV and 600 A will carry 18 MW.
(single phase calculated)
For your 3 MW, 10 to 20 kV should be enough.
20 4" pipes can hold a lot of big cables..........
Is it only 3MW? Even one fairly small hospital could easily swallow
3MW by itself, could it maybe be 30 or even 300?
Out of curiosity, how is power supplied to really large buildings, say
substations are installed in them? I would guess they would take in at
3 MW is a small value for 15 hospitals. i think an energy like 1000 kW or
more would be needed per hospital.
aykut from tr
BB> They are installing an underground electrical cable in my neighborhood.
BB> It has about 20 plastic tubes 4 inches in diameter. I suppose they
BB> will have metal conductors inside. Does anybody know about this
BB> design? I suppose it is about 750kv. What if water gets inside to
BB> tube? Bill B.