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Low-Voltage Cables "Transmission and Distribution Electrical Engineering" breaks down transmission and distribution cables into five separate categories. The most basic category is "low voltage." This includes cables used for telephone wires, as well as fire-retarded and resistant cables. These cables have the lowest maximum voltage of the four groups, ranging from 50 to 1,000 volts. Medium-Voltage Cables Medium-voltage cables --- which have a maximum capacity ranging from three to 7.2 kilovolts --- are the next class of transmission and distribution lines. These cables are typically used for solid dielectric and MI/MIND purposes. High-Voltage Cables The third class of transmission and distribution cables is high voltage. These power lines can carry a maximum voltage capacity of 10 to 150 kilovolts. While these cables can be used for the same purposes as low- and medium-voltage cables, their higher threshold makes them less cost-efficient than lower-grade wires. The main purposes of high-voltage wires include oil-filled cables, as well as gas-pressure or gas-insulated ducts. Very High-Voltage Cables Like medium- and high-voltage cables, very high-voltage lines are used for solid dielectric, oil-filled and gas-insulated ducts, but in situations where a higher maximum voltage is required. These cables have a maximum capacity of 150 to 300 kilovolts. Because of their very high-voltage capacity, these are typically transmission lines and not distribution lines.

Transmission development has not kept pace with electricity generation in the 10th and 11th plan, resulting in the lack of sufficient transmission capacity. India has installed capacity of 225 GW, yet we are able to meet peak demand of only 123 GW - one of the key reasons being lack of sufficient transmission lines.

Developing countries such as China, India and Brazil have large populations and are modernizing quickly, but closing the gap with the developed world will require a large amount of electric power. HVDC is the most environmentally friendly and economical way of transmitting large amounts of electric power. Compared with AC, DC transmission needs much narrower right-of-ways, while higher voltages reduce both electricity losses and the cost of building large-scale power lines. As generation takes place further and further away, higher and higher transmission voltages are required. The highest DC transmission voltage has almost doubled during the last decade

HVDC – High-Voltage Alternating CurrentFACTS (Flexible AC Transmission Systems) DevicesGas-Insulated Substations (GIS)Superconductors / HTS CablesWide Area Monitoring Systems

Swiss-Swedish multinational corporation ABB Ltd has commissioned a $440 million transmission link in China, which is said to be the world’s longest and most powerful transmission cable. The Xiangjiaba-Shanghai project was completed in a record time of 30 months, a year ahead of schedule. The project is the first ultra high-voltage direct current transmission link in the world to start commercial operations.

Quick take: Sure, sure, the smart grid is important. But if we really want to prepare for the future -- and if we want to keep up with China -- we also need to be working on what testing and consulting firm DNV KEMA calls "the super grid" -- namely "trans-national, or even trans-continental transmission networks that facilitate the transport of high volumes of electricity across great distances." China is already well underway on high-voltage transmission. Now DNV KEMA is opening up testing facilities in Europe to help the rest of the world get with the program. – Jesse Berst

Utilities continue to face an abundance of technical hurdles, not the least of which is the transmission and distribution infrastructure. As the demand for electricity continues to grow, so do the increasing challenges of upgrading the existing infrastructure and building new transmission circuits. As a result, utilities are looking for new and innovative ways to increase circuit capacities and maintain system reliability.

Some of the above-listed disadvantages can be eliminated with the use of new technologies. In particular, disadvantages such as a complete power fault of the HVDC transmission system during short-circuits inthe AC power system and reactive power consumption can be eliminated completely, or mostly, with the use of turn-off thyristors.Several research centers are working on improving high-capacity turn-off thyristors and also on new types of converter devices for high-capacity HVDC transmission.Finally, there are several new techniques for the perfection of grounding devices, providing for decreased electro-corrosion impacts and the formation of so-called “metal return”, which precludes the working current from flowing through the ground. Other techniques aimed at perfecting HVDC technology are also being developed (Koshcheev 2001).

The need to replace old, fragile transmission and distribution (T&D) power infrastructure and inject more power into the grid is pushing electricity utilities across Southeast Asia to strengthen and expand the T&D power infrastructure. Poor grid connectivity to remote villages too is compelling electricity utilities to lay out comprehensive plans to extend electricity to new regions. As a result, the T&D substation market in the region is expected to see sustained growth.

The Southeast Asian region has an unreliable and obsolete power transmission grid which faces frequent black-outs resulting in severe losses. Power utilities in the region have geared-up and have decided to invest in power generation projects. However, the grid is unable to take this excessive pressure that will build up when this additional power is injected into the grid. This has forced the utilities to invest in transmission grid infrastructure development.

Brazil is boosting its industrial production, power capacity and enhancing its transmission and distribution infrastructure to meet the needs of its expanding economy as well as for the 2014 FIFA football World Cup and the 2016 Olympic Games.