Editing Electric power transmission (section)

== Communications ==
{{Unreferenced section|date=November 2022}}
Grid operators require reliable communications to manage the grid and associated generation and distribution facilities. Fault-sensing [[protective relay]]s at each end of the line must communicate to monitor the flow of power so that faulted conductors or equipment can be quickly de-energized and the balance of the system restored. Protection of the transmission line from [[short circuit]]s and other faults is usually so critical that [[common carrier]] telecommunications are insufficiently reliable, while in some remote areas no common carrier is available. Communication systems associated with a transmission project may use:
* [[Microwave]]s
* [[Power-line communication]]
* [[Optical fiber]]s
Rarely, and for short distances, pilot-wires are strung along the transmission line path. Leased circuits from common carriers are not preferred since availability is not under control of the operator.

Transmission lines can be used to carry data: this is called power-line carrier, or [[power-line communication]] (PLC). PLC signals can be easily received with a radio in the long wave range.
[[File:High Voltage Pylons carrying additional fibre cable in Kenya.jpg|thumb|High-voltage pylons carrying additional optical fibre cable in Kenya]]
Optical fibers can be included in the stranded conductors of a transmission line, in the overhead shield wires. These cables are known as [[optical ground wire]] (''OPGW''). Sometimes a standalone cable is used, all-dielectric self-supporting (''ADSS'') cable, attached to the transmission line cross arms.

Some jurisdictions, such as [[Minnesota]], prohibit energy transmission companies from selling surplus communication bandwidth or acting as a telecommunications [[common carrier]]. Where the regulatory structure permits, the utility can sell capacity in extra [[dark fiber]]s to a common carrier.