Editing Utility pole (section)

===Power distribution wires and equipment===
[[File:US utility pole - labeled.jpg|thumb|upright=1.1|Typical North American utility pole, showing hardware for a residential 240/120&nbsp;V split-phase [[service drop]]: <span style="color:red;">(''A'',''B'',''C'')</span> 3-phase primary distribution wires (mounted on a crossarm), <span style="color:red;">(''D'')</span> neutral wire, <span style="color:red;">(''E'')</span> [[fuse cutout]], <span style="color:red;">(''F'')</span> [[lightning arrester]], <span style="color:red;">(''G'')</span> single-phase distribution transformer, <span style="color:red;">(''H'')</span> ground wire to transformer case, <span style="color:red;">(''J'')</span> "triplex" service drop cable carries secondary current to customer, <span style="color:red;">(''K'')</span> telephone and cable television cables ]]
On poles carrying both electrical and communications wiring, the electric [[overhead power line|power distribution lines]] and associated equipment are mounted at the top of the pole above the communication cables, for safety. The vertical space on the pole reserved for this equipment is called the ''supply space''.<ref name="Florida" />  The wires themselves are usually uninsulated, and supported by [[insulator (electricity)|insulators]], commonly mounted on a horizontal beam ('''{{vanchor|Crossarm|text=crossarm}}'''). Power is transmitted using the [[three-phase electric power|three-phase]] system, with three wires, or phases, labeled "A", "B", and "C".

Sub transmission lines comprise only these 3 wires, plus sometimes an overhead ground wire (OGW), also called a "static line" or a "neutral", suspended above them. The OGW acts like a lightning rod, providing a low [[Electrical resistance and conductance|resistance]] path to ground thus protecting the phase conductors from lightning.

[[File:China utility pole.jpg|thumb|left|A joint-use utility pole in China]]

Distribution lines use two systems, either grounded-wye ("Y" on [[Circuit diagram|electrical schematics]]) or delta (Greek letter [[Delta (letter)|"Δ"]] on electrical schematics). A delta system requires only a conductor for each of the three phases. A grounded-wye system requires a fourth conductor, the [[Ground and neutral|neutral]], whose source is the center of the "Y" and is grounded. However, "spur lines" branching off the main line to provide power to side streets often carry only one or two phase wires, plus the neutral. A wide range of standard distribution voltages are used, from 2,400&nbsp;V to 34,500&nbsp;V. On poles near a [[service drop]], there is a pole-mounted step-down [[distribution transformer]] to transform the high distribution voltage to the lower secondary voltage provided to the customer. In [[North America]], service drops provide 240/120&nbsp;V [[Split-phase electric power|split-phase]] power for residential and light commercial service, using cylindrical single-phase transformers.  In Europe and most other countries, 230&nbsp;V [[three phase]] (230Y400) service drops are used. The transformer's primary is connected to the distribution line through protective devices called [[fuse cutout]]s. In the event of an overload, the fuse melts and the device pivots open to provide a visual indication of the problem. They can also be opened manually by [[lineman (technician)|linemen]] using a long insulated rod called a [[hot stick]] to disconnect the transformer from the line.

The pole may be [[ground (electricity)|grounded]] with a heavy bare [[copper]] or [[copper-clad steel]] wire running down the pole, attached to the metal pin supporting each insulator, and at the bottom connected to a metal rod driven into the ground. Some countries ground every pole while others only ground every fifth pole and any pole with a transformer on it. This provides a path for leakage currents across the surface of the insulators to get to ground, preventing the current from flowing through the wooden pole which could cause a fire or shock hazard.<ref name="Grigsby"/><ref name="Florida"/>  It provides similar protection in case of [[flashover]]s and lightning strikes. A [[surge arrester]] (also called a lightning arrester) may also be installed between the line (ahead of the cutout) and the ground wire for lightning protection. The purpose of the device is to conduct extremely high voltages present on the line directly to ground.

If uninsulated conductors touch due to wind or fallen trees, the resultant sparks can start [[wildfire]]s. To reduce this problem, [[Aerial bundled cable|aerial bundled conductors]] are being introduced.