Epsilon Archive for Student Projects

Abstract

Danger tree removal are an important part in ensuring a secure electricity supply. The definition of a danger tree according to “Svenska kraftnät” is a tree at the edge of the power line corridor, which can fall within a meter or closer to the power line. Today, danger tree removal is normally carried out every eight years. Besides cost for harvesting and administration the power line owner is also obligated to compensate the land owner when carrying out a danger tree removal.
This study has investigated how the economic costs, in the case of danger tree removal at power lines, are affected by the time interval used between felling.
Many of today's social functions are based on electricity. Something the Swedish citizen experienced in 2005, when the storm Gudrun hit the southern parts of Sweden. Hundreds of thousands households were affected when they lost power due to windthrown trees. One consequence of this, were harsher requirements for the companies responsible for the power lines, in order to be able to secure a stable electricity supply in Sweden.
The purpose of this study is to investigate if danger tree removal every eighth year is the most profitable interval. This was done by comparing the costs of danger tree removal for one year interval and for 16 years interval, between each danger tree removal, with the costs for danger tree removal every eighth year.
When the data were collected, the diameter at chest height was measured for the trees that were considered to be dangerous at the time of the data collection, or were expected to be before the next danger tree removal. Height test trees were selected subjectively to create a height curve. The data collection was carried out at a 400 kilovolt power line outside Hassela in Gävleborg County. The distance for the data collection was one kilometre long.
The result suggests that the harvesting cost and the total cost will be slightly lower when the time period between each danger tree removal becomes longer. For the eight year interval, the total cost per kilometre and year was SEK 7 239. For one year's interval, the cost per kilometre and year was SEK 11 767 and for 16 year´s interval the total cost per kilometre and year was SEK 5 945. In addition, a longer time interval resulted in a greater intrusion.
One of the conclusions of this study is that longer interval between each danger tree removal reduces the harvesting cost. On the other hand, it´s not possible to say what the landowners view on a greater intrusion is, which is a consequence of a longer time interval between every danger tree removal. A longer time interval also means a longer time that the forest inspector must try to predict the future height growth of each tree.