Safety in the event of an internal fault: modelling or tests?

To facilitate the integration into the environment of public distribution MV/LV substations installed by EDF, their size has been divided by 5 since 1950. In addition to this trend, there is a notable increase in the short-circuit power, to improve the quality of electricity, and a desire for constant improvement of the safety of personnel and property. In this context, the development of new MV/LV substations and MV switchgear cubicles, and EDF's aim to bring into general use and harmonise internal fault protections, led the authors to carry out an investigation into internal arcing phenomena and their consequences. In collaboration with the Aachen University of Technologie RWHT and Schneider Electric, they created different forms of modelling which were validated by a series of power tests. This enabled them to gain a better understanding of the physical phenomena associated with internal faults, in particular the increase in pressure, in order to specify electrical devices and their type tests with maximum efficiency.