Safety of electricity substations included in building of general purpose and in refit situations

The new standard IEC 62271–200 concerning Mediumvoltage metal-enclosed switchgear and controlgear introduces a concept of internal arc performance class IAC. It recommends a risk evaluation characterising the material as negligible or relevant risk level for the operator and the general public. Nevertheless, no reference is made in this standard to the pressure applied on the building nor to the consequences that could have an indirect effect on persons. This is taken into account by the standard IEC 61330 for prefabricated substations. No equivalent standard exists for substations inside buildings of general purpose. When the substation is located in a building: there is no way to make a full-scale test to investigate how the local conditions will affect the whole system behaviour. As a matter of fact, such a test cannot be considered because of non-repetitive surroundings.