Valve hall

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Valve hall

A valve hall is a building that houses the valves of the static inverters in a high-voltage direct current (HVDC) plant. The valves are either thyristors or older mercury arc rectifiers. Mercury arc rectifiers are usually mounted on the floor with insulators, while thyristor valves can be supported by insulators or hung from the roof. Hanging valves requires a stronger ceiling but helps the hall and inverter withstand earthquakes better than valves on the floor.

The valve hall has heating and cooling equipment to keep the valves at the right temperature (mercury rectifiers and thyristors work best within a narrow range) and to protect the equipment from weather and dust. Several valve assemblies may be connected in series to achieve the required terminal voltage.

High-voltage bushings pass through the walls of the valve hall to connect the converter transformers on one side with the DC switchyard on the other.

Usually there is an additional building nearby for control electronics, valve cooling and monitoring, station power distribution, and worker amenities. Because of the high voltages, access to the valve hall is limited while the inverter is operating, and the plant is often controlled remotely. To protect communications from interference, valve halls are shielded against radio-frequency energy.

In some HVDC plants, such as Cabora-Bassa, outdoor valves are installed in oil-immersed containers, so no valve halls or wall bushings are required.