Economic impact of in-situ coating technology for insulation of distribution lines

Statistical data indicate that, by average, more than 50% of the faults in 22 kV and 11 kV Swedish power distribution systems are weather-related. Especially the recent events (Gudrun, etc.) contributed to the statistics significantly. A majority of outages involving 22 kV and 11 kV systems requires more than 1 hour clearing time. Maintenance and renovation costs for the electrical transmission and distribution system in Sweden amount to about 2 billion SEK per year. A sizeable portion of the maintenance costs are related to broken insulators and insulating materials. Adding similar interruptions for the railway 15 kV system, the costs and outage hours will be significantly higher.

The Swedish ¿situation¿ ¿ very large distances between generation of power and users ¿ makes it very costly to install underground cables. Hence, overhead distribution lines will remain important in Sweden for a very long time. An international trend is that the insulated conductors in power lines are becoming more dominant. Firstly, insulated conductors are used for increasing safety in the vicinity of distribution lines. Secondly, the insulating polymeric coatings reduce a risk for direct outages in cases when conducting and grounded objects fall on lines. In Sweden power outages caused by falling trees and branches are quite frequent during the autumn ¿ spring periods. The situation could be improved if, in the trouble spot locations, isolated conductors could replace the uncovered ones, but the replacement is very costly. It is also very fortunate that activities in Sweden on covered conductors started about 15 years ago. A solution with a rubber tube had been developed earlier. However, appearance of some technical problems led to abandoning this idea.

We attempt to revitalise the idea through proposing to develop a new technology for in-situ coating of the existing conductors with polymeric insulating layers. Application of this technology would reduce the failure occurrences and the cost of installation significantly.

Before submitting the proposal for further consideration by financing organisations, a thorough economic analysis of the costs involved and of the expected gains is necessary. The main advantage of the proposed technology relies on the use of already existing conductors. They would not need to be replaced for introducing the insulated lines.

The proposed examination work project will therefore concentrate on performing life cost analyses of the proposed new solution in comparison to the traditional one based on installation of ready made insulated conductors.