Given the recent large seismic activities around the world and the increase in focus on the energy industry since the Fukushima nuclear crisis, the UK has issued its own report:

“Japanese earthquake and tsunami: Implications for the UK nuclear industry” HM Chief Inspector of Nuclear Installations September 2011.

This report attempted to apply relevance to the UK from the Fukushima nuclear crisis and clearly details the tsunami and earthquake experiences in Japan.

“ The direct causes of the nuclear accident at Fukushima, a magnitude 9 earthquake and the associated 14m high tsunami, are far beyond the most extreme natural events that the UK would be expected to experience..”

On review of National Grid Electricity Transmissions current policy there is no mention of a design standard for seismic activity in the UK. Substation equipment and some civil structures are however, designed to withstand short circuit current faults which is expected to exert a greater force on the civil structures than the largest earthquake expected to be seen in the UK.

Objectives

To provide assurance that the current design specification is adequate to cope with the largest credible earthquake in the UK.

The objective of this project is to provide assessment information relating to structures selected from two example substations and for two transmission towers. The two substation configurations to be considered are a gas insulated substation (GIS) and an air insulated substation (AIS) ensuring the largest section of civil structures can be covered. The locations were chosen in order to take account of particular structures and that reside in the highest peak ground accelerations across the UK as stated in a British Geographic Study.

Two types of transmission tower types have been selected to be analysed, these are the structure type - L2 and L6. These represent a high population of the overall number of towers on the system.