BAM simply explained
High-voltage pylon
In November 2005 a major power failure occurred in Münsterland, North Rhine-Westphalia, resulting in a wide-area black-out. 250,000 people were left without electricity, some of them for up to 50 hours. Five long-distance power lines of a utility company had been heavily damaged by ice and snow build-up and dozens of high-voltage pylons collapsed. What or who was to blame for the mishap? The Federal Network Agency (Bundesnetzagentur) commissioned BAM to prepare an expert opinion. The experts tested parts of the collapsed pylons. They were particularly interested in those components which had failed under the extreme load. The experts found out that in addition to the extreme loads caused by the adverse weather, further factors contributed to the failure of the pylons. Some of them had been erected in the sixties and some components were made of a steel which was manufactured using the Thomas method. It is known that Thomas steel may become brittle over the course of time. That was also clear to the utility company concerned. Therefore, in a remedial action, it exchanged those parts of the high-voltage pylons which were under particularly heavy load. The standards applicable for the establishment of high-voltage pylons were adhered to. However, BAM verified that one pylon, which was first to collapse, had been remediated; further pylons then collapsed like dominos. An unusual concatenation of different factors had thus led to the failure of the pylons. Discussions are now ongoing in relevant circles on the appropriate form of remediation.
Through its expert opinions, BAM contributes to the clearing-up of cases of damage. The results of damage analyses quite often leads to new information about material properties, improper design, unknown loads or lack of regulations.
More information:
Working group Safety of Technical Systems and Damage Analysis (in
German)
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