View source for Path 27

{{Short description|Electrical transmission line in Southwestern United States}}
{{Distinguish|Path 26|text=[[Path 26]], a set of AC electrical transmission lines in California}}
{{Infobox transmission line
|name=Path 27
|photo=IntermountainHVDCline.jpg
|caption=Path 27 as seen on U.S. Route 50 in Utah. An AC transmission line has since been built alongside this segment of the HVDC line.
|map={{maplink |type=line |frame=yes |plain=yes |frame-align=center |zoom=4}}
|country=[[United States]]
|state=[[Utah]], [[Nevada]], [[California]]
|direction=Southwest
|start=[[Intermountain Power Plant]] near [[Delta, UT]] <br />{{coord|39|30|27|N|112|34|49|W|type:landmark}}
|through=[[Southern Nevada]]
|finish=[[Adelanto Converter Station]] in [[Adelanto, CA]] <br />{{Coord|34|33|4|N|117|26|14|W|type:landmark}}
|owner=[[Intermountain Power Agency]] (IPA)
|operator=IPA|substation_manufacturer=[[ASEA|Asea]],{{Efn-la|''[[ASEA|Asea]]'' and [[Brown, Boveri & Cie]] were merged to [[ABB Group|ABB]] on January 1, 1988.|name=Asea|group=lower-alpha}} <br />[[ABB Group]] (2011 upgrade)
|construction=May 1, 1984
|est=September 16, 1985<ref name= "UPI">{{Cite web |date=September 17, 1985 |title=Construction of the Intermountain Power Project's 490-mile transmission line... |url=https://www.upi.com/Archives/1985/09/17/Construction-of-the-Intermountain-Power-Projects-490-mile-transmission-line/3477495777600/ |access-date=2023-01-04 |website=UPI |language=en-US}}</ref>
|construction_cost=$1.1 billion<ref name= "UPI" />
|type=[[overhead transmission line]]
|current_type=[[high-voltage direct current]]
|length_mi=488|capacity=2,400 [[megawatt|MW]]<ref name="Hitachi">{{Cite web |title=Intermountain Power Project; Case Study |url=https://www.hitachienergy.com/us/en/about-us/case-studies/intermountain-power-project |access-date=December 14, 2022 |website=Hitachi Energy}}</ref>
|DC_voltage=±500 [[kilovolt|kV]]{{Efn-la|The symbol ± denotes a dual voltage power supply for a bipolar system of 500,000 V and -500,000 V.|name=Dual voltage|group=lower-alpha}}
|poles_no=[[bipole|2]]
|circuits_no=1
|website=https://www.ipautah.com/}}
'''Path 27''', also called the '''Intermountain'''{{Efn-la|More formally the '''Intermountain Power Project Direct Current''' ('''IPP DC''') '''Line'''.<ref name="WECC path">{{cite web|title=WECC Path Reports|url=http://www.wecc.biz/library/StudyReport/Documents/Path_WriteUps.pdf |publisher=WECC|accessdate=5 July 2023}}</ref>{{Rp|page=144}} |lead=yes |group=lower-alpha |name="Intermountain"}} or the '''Southern Transmission System''' ('''STS'''),<ref name=":6">{{Cite web |last1=Beshir |first1=Mohammed J. |last2=Bjorklund |first2=Hans |date=2012 |title=Upgrading the Intermountain HVDC Project to handle 480 MW additional Wind Power |url=https://search.abb.com/library/Download.aspx?DocumentID=9AKK105713A1118&LanguageCode=en&DocumentPartId=&Action=Launch |access-date=December 14, 2022 |website=ABB Library |publisher=Cigre}}</ref><ref>{{Cite web |date=December 9, 2022 |title=Early Power Generation |url=https://waterandpower.org/museum/Early_Power_Generation.html |access-date=2022-12-09 |website=Water and Power AssociatesEarly Power Generation}}</ref><ref name="STS">{{Cite web |title=Southern Transmission System Project |url=http://scppa.org/page/Southern-Transmission-System |access-date=28 December 2022 |website=Southern California Public Power Authority}}</ref> is a [[high-voltage direct current]] (HVDC) [[electrical transmission]] line running from the [[Coal-fired power station|coal-fired]] [[Intermountain Power Plant]]<!--{{Coord|39|30|2|N|112|34|51|W|type:landmark_region:US-UT|name=Delta Static Inverter Plant - Intermountain transmission line (north end)|display=inline,title}}--> near [[Delta, Utah]], to the [[Adelanto Converter Station]] <!--{{Coord|34|33|4|N|117|26|14|W|type:landmark_region:US-CA|name=Adelanto Static Inverter Plant - Intermountain transmission line (south end)}}--> at [[Adelanto, California]], in the [[Southwestern United States]]. It was installed by [[ASEA|Asea]], a company based in [[Sweden]], and commercialized in July 1986. The system is designed to carry power generated at the [[Power station|power plant]] in Utah to areas throughout [[Southern California]]. It is owned and operated by the [[Intermountain Power Agency]], a cooperative consisting of six [[Los Angeles]]-area cities, the largest member being the [[Los Angeles Department of Water and Power]] (LADWP), and 29 smaller Utah municipalities.<ref name="LAT_IM-1">{{cite news |last=Roth |first=Sammy |date=2019-07-11 |title=Los Angeles is finally ditching coal — and replacing it with another polluting fuel |newspaper=[[Los Angeles Times]] |url=https://www.latimes.com/business/la-fi-utah-coal-los-angeles-climate-20190711-story.html |access-date=2020-08-19 |quote=Utah’s Intermountain Power Agency owns the coal plant and the power line, known as the Southern Transmission System.}}</ref><ref name=":2">{{cite web |title=Participants & Service Areas |url=https://www.ipautah.com/participants-services-area/ |url-status=dead |access-date=2020-08-19 |publisher=Intermountain Power Agency |archive-date=2020-08-03 |archive-url=https://web.archive.org/web/20200803084032/https://www.ipautah.com/participants-services-area/ }}</ref>

Path 27 consists of an [[overhead power line]] {{convert|488|mi}} long,{{Efn-la|The circuit length is twice the value at {{convert|976|mi}}.|group=lower-alpha|name=Circuit length}} and is capable of transferring up to 2,400 [[megawatts]] (MW) of power at ±500 [[kilovolts]] (kV),{{Efn-la|name=Dual voltage|group=lower-alpha}}{{Efn|The [[American National Standards Institute]] (ANSI) classifies 500 kV as "[[High voltage#Definition|extra-high voltage]]" along with 345 kV and 765 kV.<ref name="C84.1">{{cite web | url=https://electrical-engineering-portal.com/the-choice-of-system-voltage-according-to-ansi-standard-c84-1 | title=The choice of system voltage according to ANSI standard C84.1 | publisher=Electrical Engineering Portal | date=August 20, 2014 | accessdate=26 November 2022 | author=Csanyi, Edvard}}</ref>|name=ANSI|group=lower-alpha}} higher than the power plant's operational output of 1,900 MW. The resulting maximum current is 4,800 [[ampere]]s.{{Efn-la|1=Calculated by: ''A'' = ''W'' ÷ ''V'', where ''A'' = amperes, ''W'' = watts, and ''V'' = volts.|name=Max. current|group=lower-alpha}} Given its length, a [[direct current]] (DC) is preferred to the more common [[alternating current]] (AC) as it allows the electrical energy to [[Direct-current transmission|travel farther]] with minimal loss to [[Electrical resistance and conductance|resistance]] and requires no intermediate stations. It is [[Bipole|bipolar]], meaning that it has two conductors of opposite [[Electrical Polarity|polarity]] (in place of three conductors for AC lines). Both conductors for the entire length are three cables [[Bundle conductor|bundled together]]; this is done to reduce the effects of [[Electromagnetic interference|EM interference]] and enhance the power line's performance. At each end of the line is a [[HVDC converter station|converter station]] that changes [[Rectifier|AC to DC]] on one side and [[Power inverter|back again]] on the other. Each terminus also features a dedicated [[Ground (electricity)|ground]] which is connected by an [[electrode line]] to a grounding site away from the converters to provide ample [[Earthing system|earth return]]; this helps protect the main line and equipment from [[Electrical fault|faults]], and allows the system to operate at partial capacity when one conductor is out of service.

Sections of Path 27 are paralleled by other AC transmission lines, including some of 500 kV. The powerline is also visible from the [[Interstate 15]] which it passes over multiple times.<ref name="IPP EIS">{{Cite report |year=1979 |title=Intermountain Power Project Environmental Statement |url=https://books.google.com/books?id=0T7RXLr39CMC|publisher=[[Bureau of Land Management]] |issue=final}}</ref>{{Rp|page=14|location=ch. 9}} The HVDC line's converter stations will be replaced as part of a project to [[Repowering|repurpose]] the Intermountain Power Plant as a [[Gas-fired power plant#Hydrogen|hydrogen-burning facility]]. The stations are expected to go online by June 2026.

== Overview ==
[[File:Western US electrical power transmission map Path 27 annotated2.png|alt=Map of WECC's transmission grid. Path 27 can be seen as a diagonal line labeled "27" between central Utah and southern California.|thumb|Rough chart of WECC's transmission grid, with Path 27 highlighted in {{Highlight|yellow}}.|572x572px|center]]

=== Background ===
[[File:DcOver247.jpg|thumb|Path 27 may be identified by its uniquely-designed steel lattice [[Transmission tower|pylons]] and two conductors. The tower's height, [[Insulator (electricity)|insulation]], and separation of conductors and their thickness meet the specifics for a 500-kV circuit. Compare to a lower-voltage, conventional three-phase power line on the right.|left|260x260px]]
[[High voltage]]s are typically needed to convey large quantities of [[Electric power|electrical power]] over a vast distance, while also minimizing the amount of energy lost to [[Electrical resistance and conductance|resistance]] in the [[Electrical conductor|conductive cables]] as a byproduct from a high [[Electric current|current]]; that is, raising the [[voltage]] lowers the amperage for the circuit, according to [[Ohm's law]].<ref name="Transmission">{{cite AV media |url=https://www.youtube.com/watch?v=qjY31x0m3d8& |title=How do Electric Transmission Lines Work? |date=September 24, 2019 |medium=YouTube |publisher=Practical Engineering |people=Grady Hillhouse}}</ref> Whereas [[Electric power transmission|high-voltage transmission]] routes commonly employ a [[Three-phase electric power|three-phase]] [[alternating current]] (AC) to move electricity in a to-and-fro fashion, [[high-voltage direct current]] (HVDC) lines, such as Path 27, carry power in only one direction. A [[direct current]] (DC) also incurs less loss of energy than AC over the same distance;<ref name="Kim-3">[[#Wiley |Wiley, ''HVDC Transmission'']], p.&nbsp;3</ref> in other words, DC can sustain power much further than AC, which may require intermediate stations, or "taps", along the route.<ref name=":0">{{Cite web |last=Mughees |first=N. |date=February 7, 2021 |title=HVDC vs HVAC power transmission systems |url=https://insights.globalspec.com/article/15927/hvdc-vs-hvac-power-transmission-systems |access-date=November 24, 2022 |website=Engineering360}}</ref> Another disadvantage for AC is that power tends to flow on the outer layer of the conductor, a phenomenon called the [[skin effect]]. DC eschews this problem; it allows power to penetrate the entire thickness of the conductor for optimal capacity.<ref name=":9">[[#Padiyar|Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;2</ref> Finally, DC circuitry has been chosen for Path 27 because the cost of transmitting power over its distance is lower than with AC,<ref name=":0" /> which is best economically suited for shorter stretches.<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], pp.&nbsp;2-3</ref><ref>[[#Wiley |Wiley, ''HVDC Transmission'']], pp.&nbsp;7-8</ref>{{Efn-la|From an investment standpoint, constructing overhead AC lines is cheaper than HVDC lines when the length is below 400 miles (600 km). Up to 500 miles (800 km) and beyond, however, makes HVDC a more attractive option. This range is called a "break-even distance." ''See also: [[High-voltage direct current#AC network interconnectors|AC network interconnectors]].''|group=lower-alpha}} HVDC is also cheaper because it utilizes fewer than three conductors, translating to less materials and subsequently allaying the cost of infrastructure and equipment used.<ref name="Kim-3"/><ref name="Allumiax">{{Cite web |date=November 5, 2020 |title=High Voltage Direct Current HVDC Transmission |url=https://www.allumiax.com/blog/high-voltage-direct-current-hvdc-transmission |access-date=2023-01-04 |website=Allumiax |language=en}}</ref>

[[ASEA|Asea]], a multinational electrical supplier based in [[Sweden]], managed the framework and supplies for Path 27, and was a chief contributor for the power line's installment.<ref name="ABB">{{citation |title=The second HVDC transmission to Los Angeles |url=http://new.abb.com/systems/hvdc/references/intermountain-power-project |publisher=ABB |accessdate=2015-08-15}}</ref> The number in "Path 27" is assigned by the [[Western Electricity Coordinating Council]] (WECC), which oversees the electrical transmission grid across the [[Western United States|American West]], to distinguish this line from the other [[WECC Intertie Paths|critical transmission routes]] in the region.<ref name="WECC path" />{{Rp|pages=4-5}} A 2010 report indicated that Path 27 was also the most [[Transmission congestion|congested electrical pathway]] within WECC's territory,<ref>{{cite web |last1=Lesieutre |first1=Bernard C. |last2=Eto |first2=Joseph H. |date=October 2003 |title=Electricity Transmission Congestion Costs: A Review of Recent Reports |url=https://www.energy.gov/oe/articles/electricity-transmission-congestion-costs-review-recent-reports |access-date=July 5, 2023 |publisher=[[US Department of Energy]] |page=1 |quote=[[Transmission congestion]] occurs when there is not enough transmission capability to support all requests for transmission services, and in order to ensure reliability, transmission system operators must re-dispatch generation or, in the limit, deny some of these requests to prevent transmission lines from becoming overloaded.}}</ref> though the system is able to handle such heavy usage.<ref name="WECC path" />{{Rp|page=145}}

Path 27 is owned and operated by an inter-municipal syndicate known as the [[Intermountain Power Agency]] (IPA), thus lending it the alternative name Intermountain.{{Efn-la|name="Intermountain"}} The IPA's roster includes 29 Utah municipalities (amidst them two suburbs of [[Salt Lake City]], and [[Logan, Utah|Logan]] as the northernmost participant) and six [[Southern California]] cities.<ref name="fiscal">{{cite report |last=Crispin-Little |first=Jan |date=October 2003 |title=The Economic and Fiscal Impacts of Expanding the Intermountain Power Project |url=https://gardner.utah.edu/wp-content/uploads/2015/09/Sep-Oct-2003.pdf?x71849 |accessdate=23 June 2023 |publisher=[[University of Utah]] |pages=1–3}}</ref><ref name=":2" /> The cooperative was founded around this mission:{{Clear}}{{Quote frame|[Intermountain Power Agency’s mission] is to utilize its assets to provide reliable, economic and legally compliant energy products and services for the benefit of its Purchasers, members, and other stakeholders, which includes supplying a ready energy resource reserve and supporting direct and multiplier economic contributions to rural communities and the State.|IPA|align=center|width=70%}}Among its objectives is funneling excess energy to communities in Southern California; Path 27 was built to fulfill that purpose. The topmost SoCal client by population on the list is the [[Los Angeles Department of Water and Power]] (LADWP), the preeminent utility provider for [[Los Angeles]], which also receives the greatest share of power through the [[Power purchase agreement|plan]] ahead of [[Anaheim, California|Anaheim]], [[Riverside, California|Riverside]], [[Pasadena, California|Pasadena]], [[Burbank, California|Burbank]],<ref>{{Cite web |last=Bleveans |first=Lincoln |date=13 March 2014 |title=Where Does Burbank's Power Come From? |url=https://www.burbankwaterandpower.com/images/administrative/downloads/Intermountain%20IPP-Read%20More_Final.pdf |access-date=28 December 2022 |website=Burbank Water and Power}}</ref> and [[Glendale, California|Glendale]] (as shown in the table below). Altogether, these members acquire the biggest proportion of energy under the IPA.<ref name="Delta's future">{{Cite web |date=2022-05-19 |title=This tiny Utah town could shape the West's energy future |url=https://www.latimes.com/environment/newsletter/2022-05-19/this-tiny-utah-town-could-shape-the-wests-energy-future-boiling-point |access-date=2023-04-11 |website=Los Angeles Times |language=en-US}}</ref>
{{Clear2|left}}
{| class="wikitable" style="float: center; font-size: 100%; text-align: center; border: 1px solid #BBB;"
|+<big>End-Users of Path 27</big> '''<br /><small>(based on net rating of 1,800 MW)</small>'''
|LADWP
|48.617%
|-
|Anaheim
|13.225%
|-
|Riverside
|7.617%
|-
|Pasadena
|4.409%
|-
|Burbank
|3.371%
|-
|Glendale
|1.704%
|-
|'''Total'''
|'''78.943%'''
|-
| colspan="2" |<small>Source: [https://www.ipautah.com/participants-services-area/ Participants & Services]</small>
|}

=== History ===
The earliest concept of Path 27 likely originated in 1973, coinciding with an [[1970s energy crisis|energy crisis of that decade]] plaguing the U.S. During that year, after the [[U.S. Bureau of Reclamation]] warned of a forthcoming energy shortage, representatives for the Utah-based Intermountain Consumer Power Association (ICPA) convened with Southern California localities in a quest for newer power sources and for investors.<ref name="IPP EIS"/>{{Rp|page=1|location=ch. 1}} The IPA established in June 1977.<ref name=":4">{{Cite web |date=January 21, 2019 |title=Intermountain Power Project (IPP) |url=https://utahrails.net/utahcoal/utahcoal-ipp.php |access-date=2022-12-09 |website=utahrails.net}}</ref>

A crucial step for Path 27 came with the Intermountain Power Project (IPP), which emerged in 1974 as a program for financing the construction of a [[Coal-fired power station|coal-fired generator]], though it was not until 1977 that Utah's legislatures formally endorsed IPA's implementation of the project.<ref name="boomtown">{{cite report |url=https://scholarship.law.uwyo.edu/cgi/viewcontent.cgi?article=1672&context=land_water |title=Controlling Boomtown Development: Lessons from the Intermountain Power Project, Part One |last=Zillman |first=Donald |date=1986 |publisher=Land & Water Law Review |accessdate=22 June 2023}}</ref>{{Rp|page=23}}{{Efn-la|In 1977, Governor [[Scott M. Matheson]] signed into law an amendment to the Utah Interlocal Cooperation Act aimed at streamlining the creation of IPA, which soon asserted control of the IPP in 1980.<ref name="IPP EIS" />{{Rp|page=1|location=ch. 1}}|group=lower-alpha}} [[Caineville, Utah|Caineville]] in [[Wayne County, Utah|Wayne County]], UT, was one of several locations suggested for the power plant,<ref name="IPP EIS" />{{Rp|page=55|location=ch. 1}} prior to settling upon the site north of [[Delta, Utah|Delta]] in [[Millard County, Utah|Millard County]], or west of [[Lynndyl, Utah|Lynndyl]] as stated in the sanction.<ref name="IPP EIS" />{{Rp|page=77|location=ch. 8}} After clearing environmental checks, the generator broke ground on October 9, 1981, with [[United States dollar|$]]300 million in initial funds.{{Efn-la|The IPA requested an additional $900 million in 1983, one of the largest outlays by an inter-regional collateral in U.S. history.|group=lower-alpha}} The original plan called for four [[Thermal power station|thermal units]], each unit producing 750 MW,<ref name="IPP EIS" />{{Rp|page=|pages=6|location=ch. 1}} but it had decreased to two due to concerns over precipitous power demand.<ref name="fiscal" /><ref>{{Cite web |title=Project History & Location – Intermountain Power Agency |url=https://www.ipautah.com/about-ipa/project-history-and-location/ |access-date=2022-12-15 |language=en-US}}</ref> The generator's first unit was erected in 1983. The first batch of [[coal]] was delivered by train on July 2, 1985, and the first unit came online later that year. The second unit was actuated on June 13, 1987, bringing the plant to its fullest capacity of 1,500 MW.<ref name=":4" /> It would be bolstered to its present-day 1,900-MW productivity in 1989,<ref name=":6" /><ref name="industcards">{{cite web |title=Coal-Fired Power Plants in Utah |url=http://www.industcards.com/st-coal-usa-ut.htm |archive-url=https://archive.today/20130126125730/http://www.industcards.com/st-coal-usa-ut.htm |url-status=usurped |archive-date=January 26, 2013 |accessdate=2012-02-19 |work=Industcards}}</ref> hence rendering the electrical generator the [[List of power stations in Utah|largest in Utah by yield]].<ref>{{Cite web |title=The Intermountain Power Plant (IPP) is a large, coal-fired power plant near Delta, Millard County. IPP has a capacity of 1,900 MW, enough to serve roughly 1.5 million households. About 75% of the power produced by IPP is exported to Southern California. |url=https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/glad-you-asked-is-utahs-state-rock-good-bad-or-ugly/ippcoalplant/ |url-status=dead |access-date=2022-12-04 |website=Utah Geological Survey |language=en-US |archive-date=2022-12-04 |archive-url=https://web.archive.org/web/20221204163916/https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/glad-you-asked-is-utahs-state-rock-good-bad-or-ugly/ippcoalplant/ }}</ref>
{{Quote box
| title = Transmission Line Completed On Time
| quote = Completing this large and complex project on schedule is a tribute to a productive work force and excellent contractors.
| author = Mike Pontius
| source = ''[[Davis County Clipper]]''<ref name=":4" />
| align = left
| width = 25%
| border = 2 px
| bgcolor = #FEFADE
}}

However, Path 27 fully materialized when the transmission line's construction commenced on May 1, 1984, and took slightly more than sixteen months to complete.<ref>{{Cite web |date=December 9, 2022 |title=Historical LADWP Facts & Figures |url=https://waterandpower.org/museum/DWP_FACTS.html |access-date=2022-12-10 |website=waterandpower.org |page=35 |agency=Water and Power Associates}}</ref>{{Efn-la|Two HVDC lines had originally been slated, and the project would have allocated an estimated 24,400 acres of land, not counting access and service roads.<ref name="IPP EIS"/>{{Rp|pages=44-45|location=ch. 1}}}} Various American contractors were commissioned for certain aspects and segments of the line; for instance, one entity from [[Georgia (U.S. state)|Georgia]] built {{Convert|239|mi|km|abbr=out}} worth from [[Adelanto, California]] to [[Moapa, Nevada]], and another from [[Mississippi]] took on the remaining {{Convert|250|mi|km|abbr=out}} till Delta;<ref name=":4" /> but perhaps the most notable obligation for this turnkey project rested upon [[ASEA|Asea]],{{Efn-la|name=Asea|group=lower-alpha}} who imported the conductive [[High-voltage cable|cables]] and pieces for the [[galvanized]] steel-lattice support pylons<ref name="IPP EIS"/>{{Rp|page=44|location=ch. 1}} to be assembled on the spot. One phase entailed the emplacement of the pylons' cement [[Foundation (engineering)|foundations]],<ref name="IPP EIS"/>{{Rp|page=48|location=ch. 1}} which are {{Convert|20|ft|m|abbr=out|spell=in}} in average depth per pylon and vary in shape based on the tower's height and weight.<ref name=":4"/> Newspapers reported that rocky, jagged terrain often posed challenges for accessibility and had likely necessitated copious excavation and even [[Rock blasting|dynamiting]]. In all, six hundred workers were deployed for the labor.<ref name=":4" /> The line achieved revenue service in July 1986<ref name="STS" /> after the ignition of the power plant's first coal-burning unit, even though a document by LADWP attests that it might have been energized as early as December 1985.<ref>{{Cite web |title=Historical LADWP Facts & Figures |url=https://waterandpower.org/museum/DWP_FACTS.html |access-date=2022-12-10 |website=waterandpower.org |page=36 |agency=Water and Power Associates}}</ref> Depending on official tallies and news accounts, the total cost was $1.1 billion.<ref name= "UPI" />

Finally yet equally integral for Path 27 are two converter stations (''[[Path 27#Converters|see below]]''), which were inaugurated along with the transmission main, and are vital for its functionality. IPP's converter was installed in conjunction with the power generator, while the second converter in Adelanto and a tangent [[Electrical substation|switchyard]] began rising on May 26, 1985, and finished in June 1986<ref name="LADWP2011">{{citation |title=Adelanto Converter Station |url=http://bp.ladwp.com/Eastern_Stations/Adelanto/ippinfo.htm |year=c. 2011<!-- first archive.org snapshot--> |url-status=dead |publisher=Los Angeles Department of Water and Power |archiveurl=https://web.archive.org/web/20140205083640/http://bp.ladwp.com/Eastern_Stations/Adelanto/ippinfo.htm |archivedate=2014-02-05}}</ref> in time to receive freshly-borne energy from borders over. LADWP supervised the construction of the combined facility and tasked Asea with the responsibility of the accouterments.<ref name="ABB" />{{Efn-la|name=Asea|group=lower-alpha}}

==== Later history ====
Since its inception, Path 27 saw upgrades and refinements around the latter turn of the century—the IPP's latest proliferation included. At the behest of LADWP and [[Southern California Edison]], ABB Group and [[Hitachi|Hitachi Energy]] modernized the transmission line in 2008 and 2011, respectively, with improved control and protection technology{{Efn-la|Hardware in place is by [https://www.mach2management.be/ MACH2].|name=MACH2|group=lower-alpha}} alongside supplemental [[Filter (circuits)|filters]] and [[Heating, ventilation, and air conditioning|cooling systems]] at each terminal.<ref name=":6" /><ref name="Hitachi" /> This helped raise the power line's capacity to its modern-day level of 2,400 MW.<ref name="converter upgrade">{{Cite web |date=2023-03-29 |title=Hitachi to supply converter stations to multi-state 2.4 GW power line |url=https://pv-magazine-usa.com/2023/03/29/hitachi-to-supply-converter-stations-to-multi-state-2-4-gw-power-line/ |access-date=2023-04-19 |website=pv magazine USA |language=en-US}}</ref>

== Installation ==
[[File:Hvdc bipolar schematic.svg|center|thumb|520x520px|Path 27 is best illustrated in this simplified block diagram of a bipolar HVDC system.]]

=== Transmission ===
The primary component of Path 27 is the [[Electrical transmission line|transmission line]] itself, which travels a length of {{convert|488|mi}}{{Efn-la|The circuit length is twice the value at {{convert|976|mi}}.|group=lower-alpha|name=Circuit length}} entirely [[Overhead power line|aboveground]] through southwestern [[Utah]], [[southern Nevada]], and southern [[California]]. As opposed to three phases, Path 27 has two [[Electrical Polarity|poles]]; one positive ([[cathode]]) and another negative ([[anode]]);<ref name="Allumiax" /> making this a [[Bipole|bipolar]] configuration.<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], pp.&nbsp;8, 12</ref><ref>[[#Wiley |Wiley, ''HVDC Transmission'']], p.&nbsp;21</ref> It exerts 500 kV per pole, or 1,000 kV total,<ref name=":11">[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']] p.&nbsp;8</ref> and is rated for 2,400 MW,<ref>[[#IPP overview and history|IPP Station Overview and History]], slide&nbsp;6</ref> giving it a maximum current rating of 4,800 amperes.{{Efn-la|name=Max. current|group=lower-alpha}} By comparison, the [[Intermountain Power Plant]] (IPP) generates up to 1,900 MW, thus adding to the line's [[fault tolerance]]. On most HVDC systems, power can be sent in either direction;<ref>[[#Wiley |Wiley, ''HVDC Transmission'']], p.&nbsp;110</ref> Path 27 transports electricity from Utah to California under normal circumstances.<ref name="boomtown" />{{Rp|page=2}}

Any conductive material engenders [[electromagnetic radiation]] whenever electricity flows through it. A single cable carrying such high voltage would produce particularly strong [[Electric discharge|radiation]] in the form of a [[corona discharge]]<ref name=":9" /> that can deprive electrical energy and cause [[Electromagnetic interference|EM interference]] on radio and communication devices.<ref>{{Cite web |last=Daware |first=Kiran |title=Corona discharge - its effects and methods of reducing it |url=https://www.electricaleasy.com/2016/07/corona-discharge.html |access-date=2022-12-21 |website=ElectricalEasy.com}}</ref> For this reason, Path 27's conductors comprise three cables fastened together, or are [[Bundle conductor|triple-bundled]]. This not only reduces the detrimental effects of discharge,<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;110</ref> it also provides more surface area for power to flow, thereby improving transmission efficiency.<ref>{{Cite web |date=October 28, 2020 |title=Advantages of Bundled Conductors |url=https://www.electrical4u.com/advantages-of-bundled-conductors/ |access-date=2022-12-21 |website=Electrical 4 U |language=en-US}}</ref> Each cable is made of [[Aluminium-conductor steel-reinforced cable|aluminium strands enveloping a steel core]] for strength and durability,<ref name="Hackaday">{{cite web | url=https://hackaday.com/2019/06/11/a-field-guide-to-transmission-lines/ | title=A Field Guide To Transmission Lines | publisher=[[Hackaday]] | date=11 June 2019 | accessdate=26 June 2023 | author=Cockfield. Bryan | location=Very Strong Wires}}</ref> and the composite measures {{convert|1.8|in|mm}} in [[American wire gauge|breadth]].<ref name="IPP EIS" />{{Rp|page=44|location=ch. 1}}

Two [[Overhead power line#Ground wires|shield wires]] are mounted above the main conductors and shared by the same support pylons. These wires guard the power line against lightning strikes.<ref>[[#Wiley |Wiley, ''HVDC Transmission'']], pp.&nbsp;213-214</ref>{{Efn-la|Lightning storms frequently take place between July and August in parts of the Mojave Desert that Path 27 traverses. This weather pattern is due to moist air migrating from [[Baja California]] during the [[North American monsoon|monsoon season]].}}
{{Clear}}

=== Converters ===
{{Further|HVDC converter}}
Both sides of Path 27 feature a [[HVDC converter station|converter station]], which bridges electrical power between AC and DC circuitry and is ubiquitous to HVDC projects worldwide.<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], pp.&nbsp;12-14</ref> The converters are located at the IPP station north of [[Delta, Utah|Delta, UT]], and the [[Adelanto Converter Station]] in [[Adelanto, California|Adelanto]], north of [[San Bernardino, California|San Bernardino, CA]].<ref name="fiscal" /><ref name="IPP Renewal">{{Cite web |title=Intermountain Power Plant Renewal, Millard County, Utah, USA |url=https://www.nsenergybusiness.com/projects/intermountain-power-plant-renewal/ |access-date=2023-06-23 |website=NS Energy Business |language=en-US}}</ref>
{{Gallery |title=Path 27's terminals<br /><small>(Power moves from left to right of gallery)</small> |width=240 | height=240 |align=center
|File:Adelanto Converter Station.jpg
 |The Adelanto Converter Station is the end point of the HVDC line.
 |alt1=HVDC converter station with valve hall close to center of image.
}}

[[File:Pole 2 Thyristor Valve.jpg|thumb|Path 27 uses stacks of thyristor valves similar to these on the [[HVDC Inter-Island]] in New Zealand. Note the person for scale.]] The heart of the conversion process transpires in clusters of [[Electrical valve|electronic valves]] that procedurally modify the flow of electricity in a manner similar to [[Electrical switch|switches]].<ref name="valves">[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;21</ref> The type of valves on Path 27 is [[thyristor]],<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], pp.&nbsp;9, 11</ref> technology popular in HVDC since the late 1960s.<ref name=":7">{{Cite web |last1=Schulze |first1=H.-J. |last2=Niedernostheide |first2=F.-J. |last3=Kellner-Werdehausen |first3=Uwe |last4=Przybilla |first4=Jens |last5=Uder |first5=Markus |date=2022 |title=High-Voltage Thyristors for HVDC and Other Applications: Light-Triggering Combined with Self-Protection Functions |url=https://www.researchgate.net/publication/255573312 |access-date=December 15, 2022 |website=[[ResearchGate]]}}</ref><ref>{{Cite web |title=Modern HVDC Thyristor Valves |url=https://library.e.abb.com/public/1402c60973f47e72c1256fda004aead8/thyrvalv.pdf}}</ref> The valve configuration is identical for both converters: 24 stacks about {{Convert|50|ft|m}} in height of 24 valves apiece (or three "[[Thyristor#HVDC electricity transmission|quadruple-valves]]"),<ref name=":7" /> organized into twelve modules<ref name="LADWP2011" />—a single valve contains 144 thyristors.{{Efn|That amounts to 165,888 thyristors for Path 27.|group=lower-alpha}} As a matter of redundancy, the valves at both terminals are grouped two by six; should one be disabled, the other can pick up the slack above its designated capacity for a limited duration.<ref name="LADWP2011" /> The entire assemblage is housed in a hangar-like enclosure called a [[valve hall]] that protects it from the weather and airborne dust.<ref>{{Cite web |last=Tatum |first=Malcolm |date=November 20, 2022 |title=What Is a Valve Hall? |url=http://www.aboutmechanics.com/what-is-a-valve-hall.htm |access-date=2022-12-12 |website=About Mechanics |language=en-US}}</ref> The valves are affixed on tall insulators that separate them from the interior walls, floor, and ceiling; done to hinder [[Electrostatic induction|induction]] and [[Electrical fault#Ground fault (earth fault)|premature grounding]], as well as aid [[cooling]].<ref>{{Cite web |title=Converter Stations - HVDC - AlternativeUniversity.net |url=https://alternativeuniversity.net/aec/electricity/hvdc/stations/ |access-date=2022-12-12 |website=alternativeuniversity.net}}</ref> Path 27's valve halls are also fortified against earthquakes.

As the IPP converter is adjacent to the [[Power station|power plant]], electricity is generally fed into the HVDC line from this terminus. Ingress for power to the system is preceded by a row of [[transformer]]s<ref name=":10" /> that step up the voltage level to 500 kV. Next, it infiltrates the valve hall through enormous [[Bushing (electrical)|bushings]] that protect the building from damage caused by [[arcing]]. Inside the hall, the valves pipe the electrical flow from AC to DC in a complex process called [[Rectification (electricity)|''rectification'']].{{Efn-la|This process is found in most [[rechargeable battery]] appliances.|group=lower-alpha}} On the DC circuitry back outside sits a [[HVDC converter station#DC equipment|sequence of filters and reactors]] that reciprocally smooth out the DC supply<ref name=":10">[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;14</ref> and serve to cushion the facility from disturbances as a result of [[Power surge (spike)|power surges]].<ref name=":5">{{Cite web |title=Station Layouts - HVDC - AlternativeUniversity.net |url=https://alternativeuniversity.net/aec/electricity/hvdc/stationlayouts/ |access-date=2022-11-27 |website=alternativeuniversity.net}}</ref> The electricity is then sent on its way down Path 27.

The Adelanto Converter Station demarks the receiving end of the HVDC line and has relatively the same layout, but the conversion mechanism is reversed. Beyond another set of reactors and filters, the inpouring power enters the valve hall to be carried over to AC circuitry anew—this is ''[[Power inverter|inversion]]'',{{Efn-la|The ''[[solar inverter|inverter]]'' on a [[solar power system]] uses this process.|group=lower-alpha}} and it blocks any power backflow on the AC conduit from reaching the valves to enforce unidirectional movement.<ref name="valves" /> The electricity advances through a second tier of transformers before disemboguing onto diverging AC lines to be dispersed across the vicinity.<ref>[[#Wiley |Wiley, ''HVDC Transmission'']], p.&nbsp;13</ref><ref name=":5" />{{Efn|Adelanto's converter connects to a 500-kV [[busbar|bank]], so the transformers here merely act as a buffer against [[overvoltage|overvoltages]].<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;105</ref> They are reputedly the largest ever manufactured to the U.S. by ABB Group.<ref name="LADWP2011" />|group=lower-alpha}}

Ideally, Path 27 can work in the opposite direction, with the Adelanto terminal becoming a rectifier, and the IPP an inverter,<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;13</ref> although this seldom happens out of practicality.<ref name="WECC path" />{{Rp|page=147}}
{{Clear}}

=== Grounding system ===
{{Sidebar|title=Grounding node locations:|content1={{Coord|39|18|58.309|N|112|55|19.066|W|type:landmark}} <!--39.31619691817959, -112.92196284244686-->|content2={{Coord|35|2|50.427|N|116|42|13.495|W|type:landmark}}<!--35.047340922158064, -116.70374869393142-->|content3={{efn-la|The distance between Path 27's grounding nodes is approximately {{Convert|361|mi|km|abbr=out|}}.<ref name="map">{{Cite web |title=Google Maps |url=https://www.google.com/maps/@36.863829,-114.61836,7.03z |access-date=2023-06-25 |website=[[Google Maps]] |language=en}} "Measure distance" tool used.</ref>|group=lower-alpha}}}}
Like any HVDC scheme, Path 27 needs to be [[Ground (electricity)|grounded]] at both ends in order to operate with respect to the earth.<ref name=":8">[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;127</ref><ref name="electrode overview">{{Cite book |url=https://www.cigre.cl/wp-content/uploads/2017/02/Brochure-Cigre-FRancia-HVDC-Electrones-675.pdf |title=General Guidelines for HVDC Electrode Design |publisher=Cigre |date=January 2012 |isbn=978-2-85873-378-1}}</ref>{{Rp|pages=|page=3}} Grounding provides the electric current a common [[Earthing system|path back into the earth]], which serves as a neutral point for the circuit.<ref>[[#Wiley |Wiley, ''HVDC Transmission'']], p.&nbsp;229</ref><ref>{{Cite web |title=Grounding - Energy Education |url=https://energyeducation.ca/encyclopedia/Grounding |access-date=2022-11-27 |website=energyeducation.ca |language=en |ref=def}}</ref>

Even with safeguards and a substantive fault tolerance, failures on the line can and do occur, thence grounding becomes a workaround for continued reliability of the system.<ref>[[#Wiley |Wiley, ''HVDC Transmission'']], pp.&nbsp;6-7</ref> If one pole develops a [[Electrical fault|fault]], its current is diverted via the ground return to complete the circuit.<ref name="electrode siting">{{Cite web |last=Holt |first=Richard J |date=April 1997 |title=HVDC Power Transmission Electrode Siting and Design |url=https://digital.library.unt.edu/ark:/67531/metadc697480/m2/1/high_res_d/580585.pdf |access-date=November 26, 2022 |publisher=[[Oak Ridge National Laboratory]]}}</ref>{{Rp|page=3}} This de-energizes the problem conductor, while the second pole remains active.<ref name="electrode overview" />{{Rp|page=18}} In technical terms, grounding allows the power line to function as a [[High-voltage direct current#Monopole|monopole]] instead of a bipole.<ref name="electrode siting" />{{Rp|page=1}} However, it halves the line's overall capacity.<ref name="electrode siting" />{{Rp|page=3}} A pole may also be taken offline by the same means for maintenance, ensuring the safety of work crews. This contingency precludes the need to shut down the whole HVDC system and interrupt the power source, yet it is temporary, as the earth return on a bipolar system is not intended for prolonged use.<ref>[[#Padiyar |Padiyar, ''HVDC Power Transmission Systems'']], p.&nbsp;12</ref><ref name="electrode siting" />{{Rp|pages=1–3}}

HVDC exhibits significant [[Electric potential|potential]] such that the converter's onsite grounding devices are not enough to withstand alone, and a return current would otherwise cause issues at the electrical facility including rapid [[metal corrosion]],<ref name="electrode overview" />{{Rp|pages=47–50}} so the grounding nodes are set at remote locations.<ref name=":8" /> On Path 27, the IPP converter's grounding point is situated about {{Convert|22.2|mi|km|abbr=out}} southwest of the valves ([https://www.google.com/maps/place/39%C2%B018'58.3%22N+112%C2%B055'19.1%22W/@39.316196,-112.9229407,421m/data=!3m2!1e3!4b1!4m6!3m5!1s0x0:0x990030ca0bf3a7ba!7e2!8m2!3d39.3161964!4d-112.9219768?hl={language} here]), while the Adelanto converter's lies about {{Convert|53.85|mi|km|abbr=out}} to the northeast ([https://www.google.com/maps/place/35%C2%B002'51.1%22N+116%C2%B042'13.5%22W/@35.055308,-116.7166441,7125m/data=!3m1!1e3!4m5!3m4!1s0x0:0xcda7226c8bf8d8ef!8m2!3d35.0475318!4d-116.7037504?hl={language} here]) on the edge of a [[Dry lake|playa]] known as [[Coyote Lake (San Bernardino County, California)|Coyote Lake]].<ref name="map" /><ref>{{Cite web |date=2014-01-10 |title=A Pilgrimage to the Buried Electrical Network Outside Los Angeles |url=https://gizmodo.com/an-electrical-pilgrimage-to-the-buried-battery-outside-1498692476 |access-date=2022-12-09 |website=Gizmodo |language=en}}</ref>{{Efn-la|By comparison, that grounding site is about {{Convert|21|mi|km|abbr=out}} east-northeast of central [[Barstow, California|Barstow]].|group=lower-alpha}} These spots were chosen in part for high [[Electrical resistivity and conductivity|conductivity]] within the earthen minerals.<ref name="electrode siting" />{{Rp|pages=10–38}} Each node covers an area of approximately {{Convert|0.65|km2|sqmi|abbr=out|order=flip}}.

At each grounding point is an array of buried conductive rods that form an [[electrode]], marking the actual transition into the earth for the current. Within the electrodes for Path 27 are sixty rods{{Efn-la|The rods themselves are elements divided into segments interlaced with smaller cables.<ref name="electrode overview" />{{Rp|pages=22}} This allows the elements to expand and contract.|group=lower-alpha}} arranged in a circular rim about {{Convert|3000|ft|m|abbr=off}} in diameter<ref name="map" /> and spaced evenly for the best result.<ref name="electrode overview" />{{Rp|pages=|page=21}} Each rod is placed vertically to reach subterranean layers with the least [[Electrical resistivity and conductivity|resistivity]] possible:<ref name=":8" /><ref name="electrode overview" />{{Rp|pages=21, 74|page=}} IPP's electrode rods are {{Convert|87|m|ft|abbr=off|order=flip}} deep, and Adelanto's extend {{Convert|60|m|ft|abbr=off|order=flip}} downward.<ref name="electrode siting" />{{Rp|page=45}} The rods are individually encased in a [[Perforated metal|perforated-metal]] tube, or a "well", to retard corrosion.<ref name="electrode overview" />{{Rp|pages=|page=23}} The wells are filled with [[petroleum coke]] to enhance the current's connectivity into the soil.<ref name="electrode overview" />{{Rp|pages=|page=82}} Additionally, the coke regulates heat that the rod naturally emits when a current is induced;<ref name="electrode overview" />{{Rp|pages=|page=89}} this is to mitigate the electrode's impact on the surrounding environment.<ref name=":8" /><ref name="electrode overview" />{{Rp|pages=|page=79}} A series of [[jumper cable]]s radiating from the center of the circle feed the return current into the rods. At the center is a small structure perched on the surface called a [[Electrical enclosure|terminal house]],<ref name="electrode siting" />{{Rp|page=42}} which is also equipped with a transmitter that helps technicians monitor the electrode's performance.<ref name=":1">{{Cite web |title=Coyote Dry Lake Return Electrode {{!}} The Center for Land Use Interpretation |url=https://clui.org/ludb/site/coyote-dry-lake-return-electrode |access-date=2022-12-02 |website=clui.org}}</ref><ref name="electrode overview" />{{Rp|pages=133–136}} The "deep-well" setup of Path 27's electrodes is a variation of the "ring-style" electrode found on other HVDC projects such as the [[Nelson River DC Transmission System|Nelson River Transmission System]] in Canada.<ref name="electrode overview" />{{Rp|page=20}}

The converters are linked to the electrodes by a pair of conductive cables, each measuring {{Convert|908|mm2|sqin|abbr=out|order=flip}} in thickness, to enable physical contact with the earth. These are the [[electrode line]]s,<ref name=":8" /> arteries for the return current—more precisely, the electrode line carries the current to the terminal house which then injects it through the electrode.<ref name="electrode overview" />{{Rp|pages=|page=135}} Starting at both termini, the electrode line runs atop Path 27's main pylons in lieu of shield wires before branching off along a standalone set of steel [[utility pole]]s. Steel poles have been selected for their resiliency in the hot, arid locales.<ref>{{Cite web |last=Sims |first=John |date=November 6, 2019 |title=Pros And Cons Of Steel Utility Poles |url=https://www.critterguard.org/blogs/articles/pros-and-cons-of-steel-utility-poles |access-date=2022-12-10 |website=Critter Guard |language=en}}</ref> The electrode line for the IPP converter has a total length of {{Convert|48|km|mi|abbr=out|order=flip}}, and the Adelanto's extends {{Convert|95|km|mi|abbr=out|order=flip}}.<ref>{{Cite journal |last=Sibilant |first=G. |date=November 2010 |title=HVDC Ground Electrode Overview |url=https://www.epri.com/research/products/1020116 |format=PDF |journal=[[Electric Power Research Institute]] |edition=Updated}}</ref><ref name="electrode siting" />{{Rp|page=45}} Uniquely, Adelanto's electrode line [[Undergrounding|travels underground]] for its final {{Convert|2|mi|km|abbr=out|spell=in}} approximately till the grounding site.<ref name="map" /><ref name=":1"/>

The electrodes and electrode lines are distinct from the [[High-voltage direct current#Monopole|metallic return]], which would involve an extra third conductor along the span of Path 27—the former [[HVDC Vancouver Island]] being an example. Such method would likely be infeasible for its scope and magnitude.<ref>[[#Wiley |Wiley, ''HVDC Transmission'']], p.&nbsp;17</ref>

{{Clear}}

==Route==
{{Multipleimage
| direction         = vertical
| image1            = Old Spanish Trail, Utah Iron Springs - panoramio - brsolutions.jpg
| caption1          = The [[Old Spanish Trail (trade route)|Old Spanish Trail]] meanders beneath Path 27 in Utah.
| image2            = Path 27 Power Lines in California 0.JPG
| caption2          = Path 27 crossing Interstate 15 outside [[Yermo, CA]]. Three electrical lines of various voltages parallel this leg of the HVDC line.
}}

Following the regular power flow, Path 27 begins at the [[Intermountain Power Plant]] in Utah and heads briefly west before curving southward, passing over the [[U.S. Route 50 in Utah|U.S. 50]]/[[U.S. Route 6 in Utah|U.S. 6]] [[Concurrency (road)|duplex]] west of [[Hinckley, Utah|Hinkley]]. The DC line ventures through legions of dry basins and high mountains in the state due southwest; all the while crossing [[Utah State Route 21|Utah Routes 21]], [[Utah State Route 56|56]], and [[Utah State Route 18|18]]; before reaching Nevada about {{Convert|5.5|mi|km|abbr=out}} north of [[Arizona]]'s northwestern corner, simultaneously entering the [[Mojave Desert]].

Inside Nevada, Path 27 traverses the [[Mormon Mesa]], bypassing [[Glendale, Nevada|Glendale]] and crossing the [[Muddy River (Nevada)|Muddy River]]. It bisects the [[Moapa Band of Paiute Indians|Moapa River Indigenous Reservation]] lands<ref name="IPP EIS" />{{Rp|page=50|location=ch. 2}} before crossing [[Interstate 15 in Nevada|Interstate 15]] near [[Crystal, Clark County, Nevada|Crystal]]. Across [[Las Vegas Valley]], the line meets with [[Nevada State Route 564|NV 564]] while riding through the [[Frenchman Mountain]], straddles the [[River Mountains]] bypassing [[Henderson, Nevada|Henderson]], and crosses [[Interstate 11]] at [[Railroad Pass (Nevada)|Railroad Pass]] before heading into [[Eldorado Valley]]. Upon traversing the [[McCullough Range]], it descends into [[Ivanpah Valley]], missing [[Primm, Nevada|Primm]] in its north and crossing Interstate 15 again; shortly thereafter, it enters California.

Path 27 cuts across isolated, oft-rugged tracts of the [[High Desert (California)|High Desert]]<ref name="IPP EIS" />{{Rp|page=4|location=ch. 5}} while also encountering [[California State Route 127|CA 127]] north of [[Baker, California|Baker]]. Now in the [[Inland Empire]], the line proceeds through [[Victor Valley]] where it crosses [[Interstate 15 in California|Interstate 15]] once more near [[Yermo, California|Yermo]], as well as [[U.S. Route 66|old U.S. 66]] and [[Interstate 40 in California|Interstate 40]] between [[Daggett, California|Daggett]] and [[Newberry Springs]]. It then encounters [[California State Route 247|CA 247]] south of [[Barstow, California|Barstow]]. Around [[Bell Mountain, California|Bell Mountain]], Path 27 meets with Interstate 15 one last time, and then old U.S. 66 a second instance and [[U.S. Route 395 in California|U.S. 395]] near [[Oro Grande, California|Oro Grande]]<ref name="IPP EIS" />{{Rp|page=7|location=ch. 5}} before reaching [[Adelanto, California|Adelanto]], where the line arrives at its final destination of the [[Adelanto Converter Station]].<ref name="map" />

Numerous AC transmission lines parallel Path 27 throughout its course.<ref>[[#Wiley |Wiley, ''HVDC Transmission'']], p.&nbsp;384</ref> A 345-kV circuit runs beside the DC line interlinking the IPP and a [[Milford Wind|wind farm near Milford]].<ref name=":6" /> A second 345-kV circuit leading to the [[Harry Allen Generating Station]] joins Path 27 near [[Cedar City, Utah|Cedar City]]. North of [[Mesquite, Nevada|Mesquite]], both are joined by a 500-kV line connecting the decommissioned [[Navajo Generating Station]]; the three travel somewhat within eyeshot of Interstate 15 until a [[Nellis Solar Power Plant|solar park]] near Crystal. An assortment of 500-kV transmission corridors then follow Path 27 through Las Vegas Valley toward [[Eldorado Valley#Solar power|another collection of solar farms]] outside [[Boulder City, Nevada|Boulder City]]. From Ivanpah Valley onward, two more 500-kV circuits and a third of 287 kV accompany Path 27 across the desert—these three constitute WECC [[Path 46]].<ref name="WECC path" />{{Rp|page=197}} By [[Victorville, California|Victorville]], Path 27 splits from the three AC routes but is once again shadowed by others of various voltages before culminating in Adelanto. Stringing multiple circuits on the same right-of-way is often favored, as it consumes less land per mile.<ref>{{Cite journal |url=https://www.mdpi.com/1996-1073/15/21/8249/pdf |title=Power Flow Modeling of Multi-Circuit Transmission Lines |publisher=[[MDPI]] |format=PDF |first=Andrey |last=Kryukov |journal=Energies |date=4 November 2022 |volume=15 |issue=21 |page=8249 |doi=10.3390/en15218249 |accessdate=26 June 2023 |doi-access=free }}</ref>
{{Clear|both}}

== Future ==
{{See also|Intermountain Power Plant #Natural gas and green hydrogen plant plans}}

The coal-firing powerhouses at the {{Abbr|IPP|Intermountain Power Plant}} site are to be retired by 2027.<ref name="Delta's future" /><ref name="LADWP_newsletter">{{cite web |last=Tucker |first=Carol |date=21 April 2020 |title=The Future of IPP Is Green - Transforming L.A.'s Last Coal Plant to Help Reach 100% Renewable Energy |url=http://www.ladwpintake.com/the-future-of-ipp-is-green/ |access-date=2020-10-14 |work=[[LADWP]] |quote=Engineering studies had determined that 840 MW was the minimum generation capacity needed to maintain sufficient voltage for the critical transmission systems to operate reliably.}}</ref> This adheres to LADWP's wishes for reducing its dependence on fossil fuels in favor of [[Sustainable energy|greener energy]].<ref name="LAT_IM-1" /> In a renewal project announced by LADWP, the plant will be replaced with a [[Gas-fired power plant|gas-powered facility]] specially tailored for [[Gas-fired power plant#Hydrogen|harvesting hydrogen]] by 2025,<ref name="LAT_2019-11">{{cite news |last=Roth |first=Sammy |date=2019-11-19 |title=Climate change activists urge Los Angeles not to build a gas plant in Utah |newspaper=[[Los Angeles Times]] |url=https://www.latimes.com/environment/story/2019-11-19/climate-change-activists-urge-los-angeles-not-to-build-new-gas-plant-in-utah |access-date=2020-10-14 |quote=The utility plans to replace Intermountain in part with an $865-million plant that runs on natural gas. ... LADWP officials claim that without a traditional power plant at Intermountain, they won’t have the physical ability to transport solar and wind energy through the transmission line to Los Angeles. They also say they hope to eventually fuel the gas plant with clean-burning hydrogen, although the technology is still being developed and could be prohibitively expensive.}}</ref> and paired with at least two [[Photovoltaic power station|solar farms]] on nearby parcels.<ref>[[#IPP overview and history|IPP Station Overview and History]], slides&nbsp;39-40</ref><ref>{{Cite web |date=18 September 2013 |title=LADWP May be Buying Utah Sun |url=http://www.kcet.org/news/redefine/rewire/solar/photovoltaic-pv/ladwp-may-be-buying-utah-sun.html}}</ref><ref>[[#Greg |Greg, ''Intermountain Power Plant & Green Hydrogen'']], slide&nbsp;3</ref> The sources will beget 840 MW and 300 MW at peak, respectively, or 1,140 MW when combined, still lower than Path 27's maximal capacity. The renewal project also calls for both converter stations to be replaced and activated by June 2026,<ref name="converter upgrade" /><ref name="IPP Renewal" /><ref>[[#IPP overview and history|IPP Station Overview and History]], slide&nbsp;33</ref> as well as improvements to Path 27 to lengthen the power line's [[service life]].<ref>{{Cite news |date=April 2023 |title=Public Finance Team Advises the Southern California Public Power Authority on Bond Deal |work=[[Norton Rose Fulbright]] |url=https://www.nortonrosefulbright.com/en-us/news/88ab2164/public-finance-team-advises-the-southern-california-public-power-authority-on-bond-deal |access-date=July 5, 2023}}</ref>

== See also ==
* [[Pacific DC Intertie]] - a similar HVDC system running through the Western U.S.
* [[List of HVDC projects]]

== Notes ==
{{Notelist-la}}

== References ==
{{Reflist}}

=== Sources ===
<references group=""></references>
*{{Wikicite | ref = Padiyar | reference=Padiyar, K. R. (2005). HVDC Power Transmission Systems. New Age International. {{ISBN|8122401023}}}}
*{{Wikicite | ref = Wiley | reference=Kim, Chan-Ki; Sood, Vijay K.; Jang, Gil-Soo; Lim, Seong-Joo; Lee, Seok-Jin (2009). HVDC Transmission : Power Conversion Applications in Power Systems. Hoboken: John Wiley & Sons. ISBN {{ISBN|9780470822968|plainlink=yes}}}}
*{{Wikicite| reference= [https://www.utah.gov/pmn/files/839711.pdf Intermountain Power Project Station Overview and History]. Utah.gov. | ref = IPP overview and history}}
*{{Cite web |last=Huynh |first=Greg |date=July 2020 |title=Intermountain Power Project & Green Hydrogen |url=https://ww2.arb.ca.gov/sites/default/files/2020-07/ladwp_cn_fuels_infra_july2020.pdf |access-date=December 9, 2022 |publisher=LADWP |ref=Greg}}

==Further reading==
*{{cite book | title=Design, Control, and Application of Modular Multilevel Converters for HVDC Transmission Systems | publisher=John Wiley & Sons | author=Kamran Sharifabadi, Lennart Harnefors, Hans-Peter Nee, Staffan Norrga, Remus Teodorescu | date=October 17, 2016 | isbn=978-8122401028}}
*Debroy, Rupam {{Google books|title=HVDC: High Voltage Direct Current Transmission line|Wt3CBQAAQBAJ}}
*{{cite book |title=High Voltage Direct Current Transmission; Converters, Systems and DC Grids |publisher=John Wiley & Sons |author=Dragan Jovcic |date=July 2019 |isbn=9781119566618 |edition=2nd}}

==External links==
{{commons category|Path 27 (Western Interconnection)}}
* [https://www.google.com/maps/d/edit?mid=1Xwxh0knMGksBni8CxrwcZEYDLgI&usp=sharing Map of Path 27's course], including overhead electrode lines, locations of converters and grounding points, [[Google Maps]]
* [http://www.abb.com/industries/ap/db0003db004333/3ade4e1a0a27ac5ec125774b00282f7b.aspx  Intermountain HVDC transmission system], The ABB Group 
* [https://www.wecc.org/epubs/StateOfTheInterconnection/Pages/Transmission-Adequacy.aspx Transmission Accuracy] in [[Western Electricity Coordinating Council]]; Path 27's usage value listed 
* [https://web.archive.org/web/20050526185217/http://www.transmission.bpa.gov/cigresc14/Compendium/IPP.htm The Intermountain Power Project (IPP) HVDC Schema]
* [https://web.archive.org/web/20050426153127/http://www.transmission.bpa.gov/cigresc14/Compendium/Ipp+Pictures.pdf The Intermountain Power Project (IPP) HVDC Pictures]

{{GeoGroup}}

{{Power Transmission Corridors of the Western United States}}
{{Energy resource facilities in Nevada}}

[[Category:Western Interconnection]]
[[Category:Energy infrastructure in California]]
[[Category:Energy infrastructure in Nevada]]
[[Category:Energy infrastructure in Utah]]
[[Category:HVDC transmission lines]]