Undergrounding

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Undergrounding refers to the replacement of overhead cables providing electrical power or telecommunications, with underground cables. This is typically performed for aesthetic purposes, and increases distribution cost.

The aerial cables that carry high-voltage electricity (e.g., 400 KV) and are supported by large pylons are generally considered the least attractive feature of the countryside but are some of the most expensive to lay underground.

1 North America
2 Europe
3 Asia
4 Variants
5 See also
6 Links

[edit] North America

In the United States the California Public Utilities Commission's (CPUC) Rule 20 permits the undergrounding of electrical power cables under certain situations. Rule 20A projects are paid for by all customers of the utility companies. Rule 20B projects are partially funded this way and cover the cost of an equivalent overhead system. Rule 20C projects enable property owners to fund the undergrounding.

[edit] Europe

The UK regulator OFGEN permits transmission companies to recoup the cost of some undergrounding in their prices to consumers. The undergrounding must be in National Parks or designated Areas of Outstanding Natural Beauty (AONB) to qualify. The most visually intrusive overhead cables of the core transmission network are excluded from the scheme. There are also some undergrounding projects that are funded by the proceeds of the national lottery.

All low and meduim voltage electrical power (<50KV) in the Netherlands is now supplied underground. Other EU countries such as the UK and Germany are undergrounding a proportion of these cables each year.

[edit] Asia

Most electrical power in Japan is still provided by aerial cables. In Tokyo's 23 wards, according to Japan's Construction and Transport Ministry, just 7.3 percent of cables were laid underground as of March 2005.

[edit] Variants

A compromise between undergrounding and using overhead lines is installing air cables. Air cables are insulated cables spun between poles and used for power transmission or telecommunication services. An advantage of air cables is that their insulation removes the danger of electric shock (unless the cables are damaged). Another advantage is that they forgo the costs - particularly high in rocky areas - of burying. The disadvantages of air cables are that they have the same aesthetic issues as standard overhead lines and that they can be affected by storms. However if the insulation is not destroyed during pylon failure or when hit by a tree, there is no interruption of service. Electrical hazards are minimised and re-hanging the cables may be possible without power interruption.