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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.

Superconductor cables, only recently available for utility applications, uniquely solve these issues. A single distribution voltage superconductor cable can carry amounts of power normally associated with transmission voltage levels, therefore eliminating the need for multiple cables and greatly simplifying placement issues.  Superconductor cables also have a unique dual-personality; under normal conditions they conduct power very efficiently, but during faults they actually limit the amount of current that can flow through them. This eliminates the risk of substation equipment damage from excessively high fault currents when paralleling substations. The installation of superconductor cable-powered bus ties between distribution substations serve as an efficient means to utilize more effectively and fully the existing power delivery infrastructure while simultaneously increasing reliability.

Promoted by key projects including large-scale long-distance power transmission, ultra-high voltage grid construction, power grid construction in new rural areas and railway electrification reconstruction, the power transmission and distribution and control equipment industry of China achieved rapid development in 2009, with the annual sales revenue and total profit of RMB 656.19 billion and RMB 49.13 billion, a YoY rise of 15.7% and 19.5% respectively. Boosted by the fast growth of power transmission & distribution and control equipment industry, five sub-sectors mounted up vigorously in 2009. In particular, capacitor and corollary equipment sub-sectors showed the most rapid growth, with the prime operating revenue and total profit increasing by 28.3% and 63.3% respectively from a year earlier. This can be ascribed to the following three factors: firstly, China has made much progress in the development of ultra-high voltage and extra-high voltage technologies; secondly, it is the period from 2009 to 2010 that the ultra-high voltage demonstration projects in China have been constructed in succession, characterizing huge investment; thirdly, China has actively promoted the concept of energy conservation and emission reduction and paid increasing attention to voltage quality, safety and electricity saving, etc.

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

Feasibility and technical aspects of partial undergrounding of extra high voltage power transmission lines [808 KB]

The company has three manufacturing facilities producing extra and high voltage, medium voltage, and low voltage power cables and employs approximately 1,200 people. The company has also recently completed a major investment program to enhance its industrial capability. Shandong Yanggu is fully qualified by the State Grid Corporation of China (“SGCC”) to produce 110kV and 220KV cables. The company supplies energy infrastructure cables to SGCC, power generation groups and various other industries.

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

ABB, the leading power and automation technology group has entered into an agreement with Jiangsu Jingke Smart Electric Company in China to establish a joint venture that will design, manufacture and service high voltage instrument transformers from 72.5 kV to 750 kV. The portfolio will include oil and SF6 stand-alone current and voltage transformers, ring-core current transformers, GIS voltage transformers and optical transformers.