How should power supply networks, a pillar of infrastructure, be made more resilient? The key to doing so is by burying power lines.
During the large-scale power outages in Chiba Prefecture in September triggered by Typhoon No. 15, a large number of utility poles fell under strong winds, requiring an extended time to restore electricity.
If utility lines were running underground, the damage from wind could be avoided. During the Great East Japan Earthquake, the communications lines that run underground -- more resilient to earthquakes and tsunami -- inccured only about one-25th the damage wrought on utility poles that run aboveground.
In reinforcing the ability to cope with disasters, burying power lines is desirable.
Removing aboveground utility poles that would disrupt vehicular and pedestrian traffic would lead to enhanced safety on the roads. Town landscapes would also be improved.
In the world's major cities, laying power lines underground has become mainstream. There are many cases whereby the installation of aboveground power lines is regulated by ordinances and the like.
The percentage of power lines laid underground is 100 percent in London and Paris, while New York, having learned lessons from damage wrought by blizzards and the like in the past, has lifted the rate to at least 80 percent.
In Japan, on the other hand, the percentage stands at only 7.8 percent in the 23 wards of Tokyo, while it hovers at as low as 1.2 percent in the country as a whole. The development of power supply and communications cable networks with the use of utility poles was carried out from the viewpoint of realizing postwar reconstruction of the country swiftly.
Since the 1980s, however, efforts to bury power lines have been promoted in parts of the country. Yet there are still about 36 million utility poles standing aboveground and their numbers are increasing by about 70,000 every year.
The biggest reason that the removal of utility poles remains sluggish is the high cost involved.
In Japan, the formula of constructing multipurpose underground conduits, where power lines are run through the same place as communications lines, has mainly been taken. While the cost of installing utility poles is about 30 million yen per kilometer, it costs about 350 million yen per kilometer in engineering work alone in laying multipurpose underground conduits.
Overseas, the prevailing method of constructing power lines is to bury the power cables directly. Through this method, the construction cost is calculated to be less than 100 million yen per kilometer.
How about Japan also promoting the spread of this method of laying power cables directly underground?
Utilizing the already existing underground ducts, used for other purposes, is also an issue to be considered. This will make it possible to lay power lines underground efficiently.
Even if the power lines are laid underground, there is a need for such devices as transformers to be installed at certain intervals aboveground. It is important to make it easier for utility companies and other entities to win the understanding of local residents by making related apparatuses smaller and improving the construction method, for instance.
It is a generally held idea that, with regard to the cost involved with laying power lines underground, the central and local governments would assume about two-thirds of it, while power companies and others that manage the power cables would shoulder about one-third of the total cost.
The financial situations of both the central and local governments are harsh. By fixing an order of priority, it is indispensable to advance the work of burying utility lines.
Such works should be carried out intensively in urban areas where the population is large and the volume of traffic is heavy, and in areas of key tourist destinations where the protection of scenery is important.
(From The Yomiuri Shimbun, Oct. 8, 2019)
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