a valve hall is a building which contains the valves of the static inverters of a high-voltage direct current plant. the valves consist of thyristors, or at older plants, mercury arc rectifiers. mercury arc rectifiers are usually supported by insulators mounted on the floor, while thyristor valves may be either supported by insulators or hung from the roof of the valve hall. the latter required a stronger ceiling structure, however the hall and the static inverter can better survive earthquakes compared to valve structures standing on the floor.