Editing Substation (section)

==Design==
[[File:Poste Adelard-Godbout 06.JPG|thumb|In continuous operation since 1901, the [[Poste Adélard-Godbout|Adélard-Godbout]] substation in [[Old Montreal]] is Canada's oldest substation. It has a facade in clay brick with gray stone ornaments to blend in to its downtown environment.]]
[[File:Leśna%2C_Elektrownia_wodna_Leśna_-_fotopolska.eu_(129510).jpg|thumb|Substation in a castle-like building from the 1910s serves as distribution point next to the Lésna dam. It is one of several hydroelectric stations at the [[Bóbr]] river.]]
[[File:Lesna-Podlaska-trafo-180902.jpg|thumb|15 kV/400 V distribution tower in Poland]]

Substation design is aimed at minimizing cost while ensuring power availability and reliability, and enabling changes to the substation in the future.{{sfn|Finn|2019|p=68}}

Substations may be built outdoors, indoors, or underground or in a combination of these locations.{{sfn|Glaubitz et al.|2018|p=375}}{{sfn|Glaubitz et al.|2018|p=422}}

===Location selection===
Selection of the location of a substation must consider many factors. Sufficient land area is required for installation of equipment with necessary clearances for electrical safety, and for access to maintain large apparatus such as transformers. The site must have room for expansion due to load growth or planned transmission additions. Environmental effects of the substation must be considered, such as [[drainage]], noise and road traffic effects.

The substation site must be reasonably central to the distribution area to be served. The site must be secure from intrusion by passers-by, both to protect people from injury by electric shock or arcs, and to protect the electrical system from misoperation due to vandalism.

If not owned and operated by a utility company, substations are typically occupied on a long [[lease]] such as a renewable 99-year lease, giving the utility company [[security of tenure]].<ref>Chapman, A. and Broom, R., [https://www.squirepattonboggs.com/-/media/files/insights/publications/2018/02/electricity-substation-leases/energyelectricitysubstationleasesconsiderationsforutility.pdf Electricity Substation Leases: Considerations for Utility Companies, Landowners and Developers], ''[[Squire Patton Boggs]]'', originally published by ''Utility Week'', 26 January 2018, accessed 22 August 2023</ref>

===Design diagrams===
[[File:LEB substation, Tottenham Marshes.JPG|thumb|Tottenham Substation, set in wild parkland in North London.]]
The first step in planning a substation layout is the preparation of a [[one-line diagram]], which shows in simplified form the switching and protection arrangement required, as well as the incoming supply lines and outgoing feeders or transmission lines. It is a usual practice by many electrical utilities to prepare one-line diagrams with principal elements (lines, switches, circuit breakers, transformers) arranged on the page similarly to the way the apparatus would be laid out in the actual station.<ref name="Design Guide for Rural Substations" />

In a common design, incoming lines have a [[disconnector]] and a [[circuit breaker]]. In some cases, the lines will not have both, with either a switch or a circuit breaker being all that is considered necessary. A disconnect switch is used to provide isolation, since it cannot interrupt load current. A circuit breaker is used as a protection device to interrupt fault currents automatically, and may be used to switch loads on and off, or to cut off a line when power is flowing in the 'wrong' direction. When a large fault current flows through the circuit breaker, this is detected through the use of [[current transformer]]s. The magnitude of the current transformer outputs may be used to trip the circuit breaker resulting in a disconnection of the load supplied by the circuit break from the feeding point. This seeks to isolate the fault point from the rest of the system, and allow the rest of the system to continue operating with minimal impact. Both switches and circuit breakers may be operated locally (within the substation) or remotely from a supervisory control center.

With [[overhead transmission line]]s, the propagation of [[lightning]] and switching [[Voltage spike|surges]] can cause [[Insulator (electricity)|insulation]] failures into substation equipment. Line entrance [[Surge arrester|surge arrestors]] are used to protect substation equipment accordingly. Insulation Coordination studies are carried out extensively to ensure equipment failure (and associated [[Power outage|outages]]) is minimal.

Once past the switching components, the lines of a given voltage connect to one or more [[Busbar|buses]]. These are sets of [[busbar]]s, usually in multiples of three, since [[three-phase]] electrical power distribution is largely universal around the world.

The arrangement of switches, circuit breakers, and buses used affects the cost and reliability of the substation. For important substations a ring bus, double bus, or so-called "breaker and a half" setup can be used, so that the failure of any one circuit breaker does not interrupt power to other circuits, and so that parts of the substation may be de-energized for maintenance and repairs. Substations feeding only a single industrial load may have minimal switching provisions, especially for small installations.<ref name=STD11>Donald G. Fink, H. Wayne Beatty ''Standard Handbook for Electrical Engineers Eleventh Edition'', McGraw Hill 1978 {{ISBN|0-07-020974-X}} Chapter 17 ''Substation Design''</ref>
[[File:Breaker and a half.svg|thumb|right|This single-line diagram illustrates the breaker-and-a-half configuration often used in switchyards of small utilities. In large utilities the double-bus-double-breaker configuration is often preferred.]]

===Safety===
Because of the risk of electrical shock, substations are inherently dangerous to electrical workers.{{sfn|Finn|2019|p=41}} To mitigate this hazard, substations are designed with various safety features.{{sfn|Finn|2019|p=42}} Live conductors and bare equipment are kept separate, either with protected equipment, or using screens or distance.{{sfn|Finn|2019|p=42}} Based on the jurisdiction or company,{{sfn|Finn|2019|pp=46, 53}} there are safety standards with minimum required clearance between different live equipment or conductors or between live metal and the ground, which often varies with higher clearance being required for higher voltages because of the greater ability to generate [[flashover]].{{sfn|Finn|2019|pp=46–47}} To this is added the necessary space for employees to work safely and vehicles to pass.{{sfn|Finn|2019|pp=48–49}} Sometimes it is necessary to work on parts of the substation while energized, but employees must maintain a safe distance of at least {{convert|3|m}}.{{sfn|Finn|2019|p=51}} The aim to reduce substation footprints comes into conflict with ease of maintenance enhanced by including gaps where employees can safely work.{{sfn|Finn|2019|p=54}}

Underneath a substation, a mat or grid of conductors laid around {{convert|0.5 or 0.6|m}} underground provides [[ground (electricity)|grounding]].{{sfn|Finn|2019|pp=55-56}}{{sfn|Nixon et al.|2018|p=313}} This grid, which is typically copper although it may be [[galvanized iron]] in some countries,{{sfn|Nixon et al.|2018|p=313}} is used to ground circuits that are being worked on to prevent accidental re-energization while workers are in contact with a de-energized circuit.{{sfn|Finn|2019|p=56}} Often, earth rods are driven deeper into the ground from the grounding grid for lower resistance grounding,{{sfn|Nixon et al.|2018|pp=313-314}} and may be surrounded by [[bentonite]] or [[marconite]] to further reduce resistance and ensure effective grounding for the lifetime of the substation.{{sfn|Nixon et al.|2018|pp=314-315}} Above ground, the grounding conductors may be steel, aluminum, or copper. They must be thick enough to carry the expected current of a fault for 1-3 seconds and remain undamaged.{{sfn|Nixon et al.|2018|p=313}} Substation fences, typically at least {{convert|2|m}} in height, both protect the public from electrical hazards and also protect the substation from vandalism.{{sfn|Finn|2019|p=64}} Internal fences can also be incorporated to protect employees from areas that are unsafe when energized.{{sfn|Finn|2019|p=65}}