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Underground electrical cable

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Bill Browning

Jan 1, 1970
0
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?
Bill B.
 
P

Palindr☻me

Jan 1, 1970
0
Bill said:
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.
 
B

Bill Browning

Jan 1, 1970
0
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.
 
J

JohnR

Jan 1, 1970
0
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.
John

Bill Browning said:
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.
neighborhood.
 
O

operator jay

Jan 1, 1970
0
Bill Browning said:
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.
neighborhood.
It

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.

750kV can't be right. If you can confirm, pls let us know.

j
In NA.
 
U

Uwe Hercksen

Jan 1, 1970
0
Bill said:
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.

Hello,

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.

Bye
 
D

Don Kelly

Jan 1, 1970
0
Uwe Hercksen said:
Hello,

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.

Bye
 
J

John Gilmer

Jan 1, 1970
0
JohnR said:
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.
John

I agree that 750 seems a little 'high" but 30KV seems a little "low."
 
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