Main elecrical transfer lines: masts or buried? Underwater/overwater? 1

[gerhardl]

This is meant as an environmental question, future oriented.

As a mechanical engineer, with only very limited knowledge of technology for electrical transfer lines for electrical high-power long distance power transfer and engineering, I have experienced an ongoing debate in my own country (in Scandinavia) where environmental actionists have spoken against 'monstermasts' and airborne lines for electrical power transfer.

Locally I have seen masts and airborne lines with security zones (25 m each side) taking up valuable prospective building areas kilometerlong along the lines.

Any views on existing or future solutions or costs parameters for buried or aboveground alternatives freeing from masts(estethical) or protecting zones (building ground)?

Note: Scandinavian varied climate and ground: Minus 30 deg C winter to plus 30 deg C in summer, snow, rain/floods, rocks, mountain and lowlands with earth and sand, also crossing very deep fjords (seawater). Frostfree burial depth from 1 to 4 meters depending on location within the country.

Any comments appreciated!

 

[davidbeach]

Figure that an underground transmission line costs somewhere around 100 times the overhead line it would replace. Who's going to pay?

 

[waross]

To echo David;
All it takes is money. Even with underground lines you will have security zones on the surface. No-one will allow a building to be constructed above a buried transmission line.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[PHovnanian]

Think of the overhead line right of way (security zone) as a potential green belt. There are a number of compatible uses of the land under and along side such lines. Just as long as crops don't grow up into the lines.

 

[waross]

Yes think of a pastoral setting of lush green grass and herds of cattle contentedly grazing. Try not to think of the copious amounts of green house gas they are producing. grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cuky2000]

There is not doubt that cost is a major factor to determine UG vs. OH. However, sometime the lack of understanding the cable technology and associated issues confuse the decision makers.

The cost of UG (under10 times OH cost) may be attributed to significant progress in the cable technology and construction methods.
<sub>For example
- Cable technology use more eco-friendly materials. ex. polymer XLPE or mass impregnated vs. Oil filled or lead covered cable.
- Direct bury cable and splacing is feassible.
- New construction technology such as directional drilling vs. open trench help the UG lines be less intrusive.
- There are available AC insulation for 500 kV class.
- High Voltage polymer insulated cable for HVDC application is available
- Performance and reliability of UG installation is comparable with overhead lines.
- Cost of typical underground transmission is around 10 times the cost of OH lines.</sub>

 

[gerhardl]

cucky2000: Thanks! This is what I am after: facts, costs and state of the art.

I am no green fantast working against practical existing technical/economical solutions.

I do however not believe that the real difference between the two would be x100, even if the difference in cost burying the lines compared to a standard mast mounting would be 'vast'.

If we boil it down to the difference in cost for the lines itself, respective 'redy to be stretched between masts overhead' the other 'ready to be buried underground or drawn through ready buried (plastic? temperature resistent? metal?) pipelines or prebored holes or in ditches, what would the difference be for a 'typical' long distance transfer line (note!: line only, no transport, mounting,masts or digging!)

What would the difference in safety areas each side be?

There is probably a lot more a mechanical engineer has not thought about (access? risks by failure?). Comments are still appreciated!

PS. Some of the comments above seems to be based on the line of thought :'forget any new development, we already have a solution that has worked for about 100 years'.

Maybee I should have posted on the forum 'Where is engineering going the next 5 years' ? ;-)

 

[davidbeach]

Remember, that over head line uses the cheapest possible insulator, air, while the underground line has to have a very expensive insulator. The higher the voltage the higher the cost of the insulation. Air is a self healing insulator, cable insulation isn't.

 

[waross]

Air as an insulator. Cheap, light, and easy to cut and drill.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[oldfieldguy]

Failures:

An overhead line may experience many "failures" but they can likely be repaired at the spot of the failure, i.e., insulator flashovers, foreign object causing shorts, etc.

A failure of an underground cable means you get a new cable.

old field guy

 

[PHovnanian]

where environmental actionists have spoken against 'monstermasts' and airborne lines for electrical power transfer.

Locally I have seen masts and airborne lines with security zones (25 m each side) taking up valuable prospective building areas kilometer long along the lines.

To a degree, I can empathize with the environmentalists who don't like to see virgin landscape marred by towers. On the other hand, the impact of having to trench straight through undeveloped territory needs to be considered. You can string a lot of wire over the ground and leave it untouched.

The building area/view impacts of overhead lines is more an issue of aesthetics to developers. Overhead lines take up a lot of land that apartment blocks could be built on. And perhaps a few customers will balk at a view of a tower. But I live near a few OH transmission lines and, while the builder might not have liked losing the land, residents get greenbelts, hiking, cycling, horseback trails out of the deal.