page_title: Dead-end tower
section_title: Long spans
hierarchical_section_title: Dead-end tower / Long spans
caption_attribution_description: English: Low-profile 500 kV A/C single-circuit anchor towers, near Toronto, ON at Highway 410.
context_page_description: A dead-end tower is a fully self-supporting structure used in construction of overhead power lines. A dead-end transmission tower uses horizontal strain insulators at the end of conductors. Dead-end towers may be used at a substation as a transition to a "slack span" entering the equipment, when the circuit changes to a buried cable, when a transmission line changes direction by more than a few degrees, or just once in a while to limit the extent of a catastrophic collapse.
  Since dead-end towers require more material and are heavier and costlier than suspension towers, it is uneconomic to build a line with only self-supporting structures.
  Dead-end towers are used at regular intervals in a long transmission line to limit the cascading tower failures that might occur after a conductor failure. An in-line dead-end tower will have two sets of strain insulators supporting the lines in either direction, with the lines connected by a jumper between the two segments. Dead-end towers can resist unbalanced forces due to line weight and tension, contrasted with suspension towers which mostly just support the conductor weight and have relatively low capacity for unbalanced load.
context_section_description: For crossings of large bodies of water, wide freeways, or valleys, where the span width of the conductors is very long, specific constructions must be used to achieve a wider distance between the conductors, mostly to prevent short-circuits which may occur when conductors come in contact with one another due to wind or other interferences.  These towers may be built as H-frame towers, or may have each conductor placed on a single tower or mast.  In every case, these towers are built more stably than most of the other towers used, as the wide span between towers means that much greater forces are placed on these towers.
caption: Low-profile 500kv A/C single-circuit towers crossing a highway, near Toronto, ON.
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