EHV power lines underground - Costs vs Surface
EHV power lines underground - Costs vs Surface
(OP)
Does anyone have a comparison of costs and challenges for EHV distribution underground. I am interested in whether or not the lifecycle cost of a burried system is really much worse than for overhead lines.
The base case system would consist of 500kV lines delivering 1000MVA. The length underground would be 10km.
I know line burial is feasible but also wonder what the challenges would be if we opted to install the 500kV to 34.5kV transformers underground as well.
Fanciful?
The base case system would consist of 500kV lines delivering 1000MVA. The length underground would be 10km.
I know line burial is feasible but also wonder what the challenges would be if we opted to install the 500kV to 34.5kV transformers underground as well.
Fanciful?






RE: EHV power lines underground - Costs vs Surface
RE: EHV power lines underground - Costs vs Surface
My cost ratio of 10 to 12 times was just for the transmission line.
RE: EHV power lines underground - Costs vs Surface
I've read a few articles suggesting the systems cost between 2 and 5 times the surface system - this takes no account of the life-cycle costs. Do others have examples or data they can share?
Robert
RE: EHV power lines underground - Costs vs Surface
RE: EHV power lines underground - Costs vs Surface
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Regards
Marmite
RE: EHV power lines underground - Costs vs Surface
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I could believe 2 to 5 times for a 15 kV to 34.5 kV distribution circuit, but not at 500 kV.
RE: EHV power lines underground - Costs vs Surface
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I've uploaded the file just to be sure.
Regards
Marmite
RE: EHV power lines underground - Costs vs Surface
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: EHV power lines underground - Costs vs Surface
Our case is somewhat unusual though. The lines must be run through a forest with marsh-like ground surface. To complicate matters the region is classified as a 'riparian widerness'. We have an idea of how much it will cost to clear a right-of-way and of how much it will cost to drill horizontal, long-reach, conduits, the challenge is therefore to get a comparison of a) pylons and cleared ROW, vs b) underground cables, connectors, terminations etc.
Would the 2-5 ratio be correct in that case.
Also the region is very cold for most of the year so ice maybe an issue.
We know there is a risk of stakeholder objections to the lines hence the need to look at an underground option.
RE: EHV power lines underground - Costs vs Surface
If this is a serious project, you really need to carry out a study and do the cost comparison for this actual installation. Directional drilling of UG circuits is not cheap either. You should be able to get assistance from local contractors in doing a more accurate cost estimate.
RE: EHV power lines underground - Costs vs Surface
RE: EHV power lines underground - Costs vs Surface
Keith Cress
kcress - http://www.flaminsystems.com
RE: EHV power lines underground - Costs vs Surface
Yes, but it is REALLY expensive. Typically it is an oil-filled system, but I hear rumors of solid dielectric (XLPE?) 500 kV cable on the market now.
115 kV and 230 kV cables are a little more practical.
RE: EHV power lines underground - Costs vs Surface
I don't know about 500kV XLPE cables, but up to 420kV
XLPE cables on the ABB market today.
Regards.
Slava
RE: EHV power lines underground - Costs vs Surface
As far as I know in China we built a 500kV underground substation back to 1998 in northern part.
RE: EHV power lines underground - Costs vs Surface
We would of course not progress any project without a detailed engineering assessment! This thread is more for my benefit than the teams, that said there has been some useful input -especially the eureletric report.
RE: EHV power lines underground - Costs vs Surface
there are now 500KV - 1000MVA cables to IEC 62067. They have a 2500mm2 copper core, and weight 40kg/m.
RE: EHV power lines underground - Costs vs Surface
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RE: EHV power lines underground - Costs vs Surface
RE: EHV power lines underground - Costs vs Surface
Long cables are more likely to be DC, but that requires expensive converter stations at each end.
RE: EHV power lines underground - Costs vs Surface
The reason I ask is that due to the cost of offshore windfarms and the underwater cable & connectors, and the issues over planning onshore wind-farms, whether it would be feasible, if slightly more expensive to replace OH transmission lines with underground cables, and put up wind turbines in series along the previous OH transmission line.
The example would be the Denny to Beauly line which is going to be upgraded to 440kv "super-pylons"
If wind turbines need substations to connect to the Grid and underground cables need substations etc. would this not provide some joined up thinking and local generation without scenic detriment etc?
RE: EHV power lines underground - Costs vs Surface
Regards
Marmite
RE: EHV power lines underground - Costs vs Surface
And underground cabling have shunt reactors to absorb & control voltage, do turbines not work in series?
Additionally there are already a network of Transfer stations,along the route of the grid.
RE: EHV power lines underground - Costs vs Surface
Regards
Marmite
RE: EHV power lines underground - Costs vs Surface
The reason for upgrading from 275kV to 440kv is to have remote generation from renewables. This of course becomes redundant if more is generated locally as this is the environmental best option.
I understand that underground cabling is more expensive, however as suggested in
https:/
if we are looking at a mainly rural area (Scotland) which relies heavily on tourism and the exporting of oil,gas, electricity & water to England & Europe this may be an investment worth making.
I suggest that a daisy chain of turbines long a line is the same as a daisy chain round a hill.
Thanks & Best Wishes
Wildbairn