Sumitomo Electric is one of the world’s leading manufacturers of high-voltage power cables and overhead conductors. We offer a wide variety of products to fulfill many different needs, and have extensive experience with product development and installation. In 1921, we supplied the first high-voltage submarine cable in Japan, which at the time was the world’s longest submarine cable system, and since then we have provided more than 6,000 km of submarine cable to locations around the world. In 1979, we manufactured the first high-voltage underground DC cable system in Japan, and in recent years have provided HVDC cable for interconnecting power grids in Europe.

High-voltage DC cable

For HVDC applications, we offer fluid-filled cable systems, mass impregnated (MI) cable systems, and cross-linked polyethylene (XLPE) cable systems. XLPE cable is the most recently commercialized of these cable types, and they offer benefits such as capex reduction and increased operational margins. The key features of XLPE cables include polarity reversal operations with conventional LCC converters and significantly higher operational conductor temperatures than MI cables.

Some applications of XLPE HVDC cable systems:

• The UK-Belgium interconnect uses 400 kV XLPE cable to transmit electricity generated by offshore wind farms in Belgium to the UK’s electrical grid. The cable link comprises 130 km offshore and 12 km onshore cabling. This 1 GW interconnect has been in operation since 2019.
• In Germany, the Corridor A-Nord project is being constructed with 525 kV XLPE insulated HVDC underground cable. This DC link will be used to transmit the increasing volume of renewable energy generated by wind farms in north Germany to customers in the central parts of the country.
• In India, the first voltage source converter HVDC project uses XLPE cable systems for the 32 km route to supply electricity to the country’s southern region. The Pugalur-Thrissur HVDC project will have a capacity of 2 x 1 GW when it is completed in 2020.

High-voltage AC cable

We also have extensive experience with HVAC projects both underwater and underground. For underground HVAC projects, we have delivered cable installed in various ways such as direct burial, horizontal directional drilling, duct pipe installation, and vertical shaft installation. Some of the special features we have for HVAC cables include an extruded aluminum corrugated sheath to provide increased flexibility and radial strength of the sheath, better protection against moisture, and larger fault current capacity. We have also developed a unique XLPE triplex cable design to solve oil-leak problems with existing fluid-filled pipe-type cables, and offer a special anti-termite jacket made from FR polypropylene to prevent termite damage in places where this can be an issue.

Some applications of HVAC cable systems:

• In Japan, 120 km of AC 500 kV XLPE cable was installed in the Tokyo metropolitan area as part of the world’s first project to adopt 500 kV XLPE cable technology for long-distance transmission lines. This system has been in operation since 2000.
• In the US, approximately 1,850 km of 115 kV cable was installed in an HDD pipeline for a channel crossing. This installation proved to be more cost-effective and robust compared to conventional submarine cable installation.
• The San Francisco Bay Crossing uses 230 kV XLPE submarine cables with a special design to provide high tensile strength along its approx. 14 km route. This system has been in service since 2016.
• In Germany, 155 kV submarine cable is used to connect an offshore wind platform with a HVDC offshore platform in the North Sea. Service at this installation started in 2017.

Overhead conductors

We offer many types of high-quality overhead conductors in order to meet a wide range of project requirements and environmental conditions.

• HTLS (high-temperature, low-sag) conductors enable increases of transmission capacity by 1.6 to 2.0 times without replacement or reinforcement of existing towers, while maintaining the same sag level as conventional ACSR (aluminum conductor, steel-reinforced) conductors. HTLS conductors are constructed from thermal-resistant aluminum alloy with an aluminum-clad Invar core.
• High-strength & thermal-resistant conductors feature a special design that reduces sag in order to ensure adequate clearance under long spans, while maintaining high current capacity. These conductors were developed for long-distance overhead line crossings, such as a 2,300 m crossing over one of China’s major rivers. They combine extra-high-strength aluminum-clad steel with thermal-resistant aluminum alloy.
• Low-loss conductors reduce transmission loss by up to 25% compared to conventional ACSR conductors, and can also reduce CO2 emission.
• Environmental-friendly conductors reduce wind noise and sunlight reflection as a way to mitigate their impact on surrounding communities.

Cable accessories

In addition to cables, we have developed many types of cable accessories to meet a wide variety of customer requirements. One example is a metal-enclosed GIS termination for outdoor termination that complies with the IEC 62271 standard, which has a Y-branch joint for XLPE and fluid-filled cables. For joints, we offer transition joints that can be used to replace existing fluid-filled cables with new XLPE cables, and we also provide offshore joints for the installation and repair of transmission lines from offshore wind farms.

Distributed temperature sensing system

OPTHERMO is a temperature sensing system that uses an optical fiber as a sensor to continuously measure temperature along the fiber. The optical fiber is embedded inside or attached to the power cable. This method is ideal for performing real-time measurements of cable temperature over a long distance with significantly high temperature and spatial resolution. OPTHERMO can also be used for applications such as downhole monitoring of oil/gas wells, monitoring of LNG tanks, and fire detection in tunnels.