OIL FILLED HVDC CABLES 1

[peakpilgrim]

Hi
I need to find out about HVDC cables.
I recently worked on a line for 400KV HVDC and the cable was oil filled.
Please advise.
1. How is oil-filled better than any other material and how does it work
2. I understand that the oil is kept under pressure. What pressure?
3. Does the oil circulate through the cable and is it cooled at certain sections
4. Why is DC superior to AC for HVDC underground cables? I always understood that AC was used on OHLs to step up and down the voltage easier to reduce energy losses

Please advise

Cheers

Peakpilgrim

 

[Sn00ze]

Well, my knowledge is limited in this subject but from where i've seen them used is in underground transmission lines around downtown as conventional overhead transmission lines are undesirable or impossible. They are filled with oil in order to dissipate heat (again, buried and grade is not enough for heat dissipation). there are pumps on each side of the cable or in a station in between that circulates the oil within it.

here's an interesting article about it:

http://circuitglobe.com/oil-filled-cables.html