The Great Plains Expansion project includes the construction of 4,345km long, 345kV overhead transmission lines across seven US states, including Kansas, Texas, Nebraska, Oklahoma, Arkansas, Missouri and Iowa.

The proposed $4bn project consists of five key overhead transmission lines, substations, an administrative facility, and related infrastructure facilities. The first line will run from western Kansas to southern Iowa and the second will be laid between east-central Nebraska and north-central Iowa.

The third line will originate in western Oklahoma and terminate in south central Missouri, while the fourth will be built from south-west Kansas to south-central Missouri. The fifth line will stretch from eastern Texas to south-west Arkansas via southern Oklahoma.

The Great Plains Expansion project proposal was prepared by ITC Great Plains, a subsidiary of ITC Grid Development, and submitted to the Southwest Power Pool in October 2012. The project is currently in planning stage.

The Power for the Plains Transmission Program is a $3bn capital investment initiative that aims to expand and improve the electric infrastructure across Texas, Oklahoma and New Mexico through a series of power transmission line projects.

Approved by the Southwest Power Pool in 2010, the project is being developed by Xcel Energy. A total of 1,287km of transmission lines and ten substations have been built across the three states since 2011.

An additional 1,126km of power lines that are planned to be built under the project through 2021 include the 115kV Potash Junction-Livingston Ridge transmission line, the 345kV TUCO-Yoakum-Hobbs line, the 115kV Mustang-Shell CO2 line, the 115kV China Draw-Yeso Hills line, and the 115kV Bailey-New Amherst-Lamb line.

The Power for the Plains initiative, which also includes construction or refurbishment of more than 25 substations, is expected to be completed by 2022.

The 1,854km long Miracema-Sapeacu overhead transmission line is planned to be built between Miracema and Sapeaçu in Brazil, covering 47 municipalities in the states of Tocantins, Maranhão, Piauí and Bahía. The objective of the project is to expand the capacity of the National Interconnected System.

The project is being undertaken by the Brazilian electric power regulator Agência Nacional de Energia Elétrica at an estimated cost of $970m. It will involve the laying of 500kV transmission lines, interconnection of six substations, and installation of converter transformers and generators.

The plans for the transmission line project were announced in 2010 and the engineering, construction and procurement (EPC) contract was awarded to Abengoa Brasil in December 2012. The installation licence was issued by the Brazilian Institute of Environment and Natural Resources in March 2015.

The project was, however, halted in June 2016, following the liquidation of Abengoa due to financial issues.

The Ethiopia-Kenya electricity transmission interconnector is a proposed 500kV, HVDC overhead power transmission line being built between Wolayta-Sodo in Ethiopia and Suswa in Kenya. With a power transfer capacity of 2GW, the line aims to improve exchange of electricity between the two countries.

The $1.26bn interconnector has a total length of 1,045km, of which 433km will be built in Ethiopia and the remaining 612km in Kenya. The project also covers AC/DC converter substations, suspension towers, and electric feeder systems.

The memorandum of understanding for the Ethiopia-Kenya interconnector was signed between the governments of Ethiopia and Kenya in May 2006. The line is being developed by Kenya Electricity Transmission Company and Ethiopia Electric Power Corporation.

The construction works commenced in August 2016, with completion scheduled for 2019. China Electric Power Equipment and Technology was selected to build the transmission line, while the contract for the construction of substations was awarded to a consortium of Isolux Corsan and Siemens.

The Côte d'Ivoire, Liberia, Sierra Leone and Guinea (CLSG) transmission interconnector is a 1,349km long overhead transmission line that aims to increase electricity supply to the four countries.

The project involves construction of 225kV double-circuit towers and 11 substations, transmission stations, two regional control centres, and associated infrastructure.

The project is being developed in four lots. The lot one power line runs from Yekepa to Buchanan in Liberia, while the lot two will link Buchanan, Monrovia, and Mano in Liberia. The lot three will stretch from Mano to Kenema and Bikongor in Sierra Leone, while the lot four will connect Bikongor to Yiben in Sierra Leone via Bumbuna.

Construction on the $444.3m project began in June 2017, with completion scheduled for 2019. The EPC contracts for the four lots were awarded to EIFFAGE-ELECNOR joint venture, National Contracting Company, Jyoti Structures of India, and Kalpataru Power Transmission, respectively.

The 900km long Phokoje to Kasane overhead power transmission line represents the second phase of the North West Transmission Grid Connection programme, which is being implemented by the Botswana Power Corporation.

The P2.4bn ($240m) project will consist of a 400kV transmission line stretching from Phokoje to Pandamatenga through Dukwi, a 220kV line from Pandamatenga to Kasane/Kazungula, and a 132kV line from Mawana to Disaneng.

It will also include the development of a 400kV/330kV/220kV/33kV substation at Pandamatanga, a 400kV/132kV substation at Dukwi, a 220kV/66kV substation at Kazungula, as well as 220kV/33kV, 66kV/33kV and 66kV/11kV substations.

The plans for the project were announced in early 2015 and tenders were issued in December 2015 and February 2016. The construction works are expected to start in August 2019, with completion scheduled for 2020.

The Riyadh-Mecca high-voltage direct current (HVDC) overhead power interconnector transmission line runs from Riyadh to Mecca, covering the central and western parts of the Kingdom of Saudi Arabia. The plans for the construction of the line were announced in the first quarter of 2010 and the project was completed in the third quarter of 2015.

The project included the laying of power lines, installation of transformers and power-control units, and construction of substations and related infrastructure. With a total length of 800km, the line can transmit up to 3GW of power between Dharma in Riyadh and Bahra in Mecca Province.

It aims to increase network capacity in the region, while providing a reliable back-up power supply in emergency situations.

The detailed technical specifications for the $1bn transmission line project were prepared jointly by Italian company CESI Middle East and Tractebel Engineering under a contract awarded by the operator Saudi Electricity Company in November 2012.

The 754km long Luanda hydroelectric transmission line is being built to interconnect the 2.1GW Laúca hydroelectric power plant to the Capanda and Cambambe hydropower plants and the Soyo combined-cycle thermal power plant in Angola.

The project comprises construction of 400kV/220kV extra-high voltage transmission lines and installation of transformers, suspension towers, and anchor towers. It also includes construction of four new large substations at Zango, Bita, Calandula and Malange, and expansion of six substations.

The overhead transmission line is being built by Brazilian firm Odebrecht under a $797m contract awarded in November 2015. Completion of the project is scheduled for the fourth quarter of 2019.

The second 500kV overhead transmission line stretching from Yacyreta hydroelectric power station to Villa Hayes substation was inaugurated in August 2018. Built with an investment of $140m, the line interconnects the Itaipu hydroelectric dam and Yacyreta projects through the Villa Hayes substation to improve reliable electric power supply.

The 364km long line consists of two sections including a 17km-long stretch from Yacyreta to Ayolas and a 347km long section from Ayolas to Villa Hayes, while the existing Itaipu-Villa Hayes interconnection has a length of 348km.

The project also included expansion of the 500kV and 220kV yards in the Ayolas and Villa Hayes substations, as well as installation of transformers and towers.

Construction on the Yacyreta-Ayolas-Villa Hayes line began in May 2016. The works were carried out by CIEGEC consortium, formed by CIE and SOMAGEC, and Siemens-Rieder consortium, formed by Rieder & Cia and Siemens. The transmission line is operated by the National Electricity Administration of Paraguay.

Credit: Junior Braz / Shutterstock.com

The 623km long, 525kV NordLink is the first HVDC link between Tonstad, Norway, and Wilster, Schleswig-Holstein, Germany. Construction on the link began in September 2016, while commercial operations are expected to begin in 2020. The estimated cost of the project is between €1.5bn ($1.7bn) and €2bn ($2.3bn).

The project comprises a 516km subsea cable route in the North Sea, a 53km overhead line from Vollesfjord seafloor in the southern part of Norway to Tonstad in Vest-Agder county, and a 54km underground section stretching from Busum dike in northern Germany to Wilster substation in Schleswig-Holstein.

Norwegian transmission system operator Statnett is responsible for the construction of the Norwegian section of the project, while the German section will be built by DC Nordseekabel, which is jointly owned by Tennet and German state development bank KfW. Nexans Norway and ABB were selected for the construction and installation of HVDC cables.

With a capacity of 1.4GW, the transmission line will facilitate the exchange of renewable energy between the two countries.