Presentation and definition
Modular indoor substations for high and extra-high voltages

Between air-insulated outdoor substations and metal-enclosed substations (modular assembly of connections and equipment enclosed in grounded enclosures insulated with a pressurized dielectric, generally sulfur hexafluoride), modular indoor substations (MIS) are air-insulated building substations with reduced distance between live parts and metal masses, built in the form of modules, part of which is prefabricated in the factory; live parts are kept out of reach by interposing an obstacle (compartmentalized technology) or by moving away (non-compartmentalized technology).