Overhead Power Supply
Since 1999 Metro de Madrid uses a new patented system for its installations: a solid track hung from the ceiling of the tunnels, instead of the usual copper or aluminium wire. This type of catenary (or overhead line) is rigid, making it more robust and less prone to failures. Installations outside of tunnels are rare, as they require many more support structures compared to traditional wire based overhead lines, making them more expensive to install.
This system of rigid overhead power supply is also used elsewhere.
Read more about this topic: Madrid Metro
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