Comparison of overhead line lightning performance based on two different tower geometries

As a part of reinforcing the 400 kV transmission system in Jutland, Denmark, the Danish TSO is in the process of constructing a new gas insulated substation (GIS) in Revsing. This includes raising a new type of pylon, which will carry the new overhead lines to the GIS. The reliability of the substation and transmission line is of great importance as it is a part of the 400 kV backbone between Sweden, Norway, Germany and the offshore wind farms in Horns Rev, Denmark. The new Eagle pylon has been designed with the focus of minimizing the visual impacted of overhead lines. A detailed lightning performance analysis of the existing Donau and the new Eagle pylon is therefore important in order to assess the risk of failure.
The lightning strike analysis is based on the number of strikes expected to terminate on the line and an investigation of how many of these there may be expected to cause a flashover. The analysis includes an evaluation of both direct stroke and backflashover.
The analysis of direct stroke is performed from calculation of the maximum shielding failure current (IMSF), the shielding failure rate (SFR) and the shielding failure flashover rate (SFFOR).
Backflashover is evaluated using an iterative process recommended by CIGRÉ [4]. The process intends to determine the expected backflashover rate (BFR).
This analysis is performed for both types of pylons and the results compared. From this analysis it is concluded that the phase conductors on the Eagle pylon are significantly better protected from direct stroke than the phase conductors on the Donau pylon. Furthermore with respect to a backflash, the Eagle has a better performance than the Donau pylon.
It is therefore concluded that the Eagle has a better lightning performance than the Donau.