Undergrounding

Undergrounding is the replacement of overhead cables providing electrical power or telecommunications, with underground cables. This is typically performed for aesthetic purposes, but also serves the additional significant purpose of making the power lines less susceptible to outages during high wind thunderstorms or heavy snow or ice storms. Undergrounding can increase the initial costs of electric power transmission and distribution but may decrease operational costs over the lifetime of the cables.

Telegraph cable undergrounding was considered in Northern Germany as early as 1870.

The aerial cables that carry high-voltage electricity and are supported by large pylons are generally considered an unattractive feature of the countryside. Underground cables can transmit power across densely populated or areas where land is costly or environmentally or aesthetically sensitive. Underground and underwater crossings may be a practical alternative for crossing rivers.

The advantages can in some cases outweigh the disadvantages of the higher investment cost, and more expensive maintenance and management.

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.

The UK regulator Office of Gas and Electricity Markets (OFGEM) 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. Some undergrounding projects are funded by the proceeds of the national lottery.

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

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