Three-level pylon

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A three-level pylon is a pylon designed to arrange conductor cables on three crossbars in three levels. For two three-phase circuits (6 conductor cables), it is usual to use fir tree pylons and barrel pylons. Three-level pylons are taller than other pylon types, but require only a small right-of-way. They are very popular in a number of countries such as Belgium, China, and Hong Kong. However, due to their taller height, these pylons are not usually used near airports and other locations where height is an issue. Some dual-circuit power lines may switch to a two-level pylon instead or split up into two shorter, delta pylon single-circuit lines.

A barrel pylon is a common type of three-level pylon. It arranges two three-phase circuits in three levels, at which the lowest cross beam possesses a smaller span than the middle crossbar and thus a larger span than the highest crossbar. As a rule the highest and the lowest cross beam have the same span at ton masts.

In the United States, the three-level pylon is common for voltages like 115 kV and 230 kV which venture into cities with small, narrow rights of way. However, the 500 kV wire, which usually runs in rural or suburban regions, usually uses single-circuit delta-pylons instead of the three-level pylon. This is probably because there is no need to build a taller, three-level pylon dual-circuit line when there is enough space for two single-circuit lines. As a result, 500 kV dual-circuit lines are rare in the United States, with only a few instances of line in California, like Path 15 and Path 66. Bonneville Power Administration is the only utility in the United States with several barrel pylon dual-circuit 500 kV wires, located in Washington, Oregon, Idaho, and Montana^[1].

[edit] See also

• Two-level pylon
• Delta pylon

[edit] References