According to the latest findings of E.ON’s in-house investigation into the causes for the disruption to the European power grid on 4 November, that were submitted to the Federal Network Agency today, human error, as opposed to any technical malfunctions, was chiefly responsible for the outage.

Thanks to a detailed analysis of a comprehensive set of data, E.ON has already been able to largely reconstruct the chain of events that led to the disruption. The results show that an E.ON control center had assessed developments correctly and accordance with standard procedures but, owing to time pressure, had not made use of all technical options for a comprehensive situation analysis.

Prior to the scheduled deactivation of the ultra-high voltage transmission line that crosses the Ems River ahead of the passage of the Norwegian Pearl cruise ship, the control center had not checked whether the outage of an additional transmission line might overload the power grid. About half an hour later, another high voltage transmission line was overloaded – for reasons that are not yet known. To compensate for this, a number of lines were switched together at a substation. Contrary to the assessment of the control center’s staff, this did not decrease but further increased the load on the power grid, which, in turn, triggered an automatic shutdown procedure. The outage of the second transmission line therefore ultimately set off the domino effect which led to the temporary disconnection of the European interconnected power grid.

There is, however, no evidence whatsoever of any technical malfunction of the transmission lines, control or monitoring systems involved. Findings to date indicate that all systems reacted correctly and in accordance with standard procedures, effectively preventing a complete blackout. Insufficient investment in maintenance or technical infrastructure can therefore be ruled out as causes for the disruption.

Further investigation is required until all remaining issues have been resolved. These, for instance, include the cause for the rapid and unexpected increase in electricity flows through the transmission lines in question. It is not until these issues have been fully investigated that possible improvement measures can be pinpointed. In doing so, E.ON Netz intends to work closely with the Federal Network Agency and all other parties involved.

Klaus-Dieter Maubach, the E.ON Energie Board of Management Member responsible for the power grid, issued the following statement on the matter: “We deeply regret the disruption to the power supply that affected many European electricity consumers as a result of the events of 4 November. We were quickly able to identify the main cause for the disruption but will continue to press ahead with our investigations until all remaining questions have been answered to our full satisfaction.”