Catenary
Pennsylvania Railroad Style: Front and Side Views

front view:

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side view:

About overhead wires

The Pennsylvania style shown above was an effective way of building a high speed electricity delivery system, lasting from the early 20th century into the 21st century. A problem in a rigid system such as this is the expansion and contraction of metal with temperature: slack in the trolly (or contact) wire can cause snagging with the pantograph. Tensioned systems, where the contact wire is in (more or less) mile long lengths, tensioned with hanging weights on the ends, can eliminate this and other problems. Much of the remaining Pennsylvania has been converted, as has the New Haven's distinctive system of triangular hangers.