(Repeats earlier item. John Kemp is a Reuters market analyst. The views expressed are his own)
By John Kemp
LONDON, June 19 (Reuters) - China's power engineers have become world leaders in ultra-high-voltage transmission systems connecting far-off power sources with cities hungry for electricity.
China already has seven ultra-high-voltage (UHV) lines in operation, more than any other country, carrying power over thousands of kilometres at around 800,000 or even 1 million volts.
In April, the government gave the go-ahead to build another line operating at 1 million volts between rural Anhui province and the cities of Nanjing and Shanghai.
The National Energy Administration, which is part of the powerful National Development and Reform Commission, the country's top economic regulator, has ambitious plans for as many as 12 inter-regional ultra-high-voltage transmission corridors spanning the country.
Most of the existing and planned transmission lines run broadly west to east and are intended to take power from western and central regions, where there are abundant hydro, coal, gas, solar and wind resources, to major industrial cities near the east coast.
With so many projects planned, State Grid Corp of China (SGCC) is looking forward to a "golden era" of UHV development at home and likens its UHV experience to a "golden business card" to help it win business overseas, according to a company release ("China enters a golden era of UHV development", May 16).
State Grid says UHV will give China a unified national electricity market for the first time as well as helping to meet booming electricity demand and cut pollution.
UHV is intended to link the country's existing regional grids in a national network. But it is also meant to herald much bigger changes in the way China uses energy.
SGCC wants the coal- and oil-fired boilers used in factories, offices and district heating systems across northern China to be replaced by electric heating to cut the air pollution that kills millions of people every year.
Much of the electricity for the grid would still be generated from coal, a source of greenhouse emissions as well as air pollution.
But large central power stations are likely to be more efficient than the small and old boilers used in many northern areas to provide winter heating, and it would be easier to fit them with scrubbers and other technology to cut pollution.
Shifting from coal to electric heating would also enable China to integrate more clean sources of power such as wind and solar into the energy mix.
State Grid calls it the "coal-to-electricity" programme and says it would help meet many of the government's plans for increasing energy efficiency, cutting pollution, and reducing dependence on imported oil.
Coal-to-electricity aims to replace coal-burning stoves for industrial and residential purposes with electric ones to curb air pollution, SGCC Executive Vice-President Yang Qing told a conference on green electricity in November 2013.
Oil-to-electricity could help develop the market for electric vehicles and electric irrigation in rural areas, to cut reliance on gasoline and diesel, Yang explained ("SGCC proposes coal-to-electricity to control smog", Xinhua, Nov. 8, 2013).
Under a programme launched last year, SGCC intends to replace many district heating boilers with large-scale heat pumps, according to Xinhua.
SGCC's strategy for cleaning up China's pollution problem and cutting greenhouse emissions is essentially similar to the climate plans being pursued by governments in Europe and North America.
The strategy consists of two separate transitions: electrification and decarbonisation. It would shift more energy consumption away from direct use of fossil fuels onto the electricity grid, then cut emissions from power plants by replacing fossil fuels with more renewables and nuclear power.
China's problem is that main sources of fossil fuels and renewables for power generation are hundreds and even thousands of kilometres from where the electricity is most needed.
All transmission systems lose energy between generation and the end consumer as the electricity encounters resistance in the wires along the way and some energy is lost as heat.
On average, about 6 percent of the electrical energy transmitted and distributed in the United States was lost between 1990 and 2012, according to the U.S. Energy Information Administration.
The further electricity is transmitted, the more is lost. Economic considerations therefore tend to cap transmission distances.
One reason why solar power stations in North Africa and the Sahara cannot currently be used to supply electricity to Northern Europe is that the transmission losses would be too great.
But it is possible to reduce the proportion of energy lost by stepping up the voltage, which is why China and a number of other countries have begun developing ultra-high-voltage systems to carry power over much longer distances.
In the United States, most long-distance transmission lines operate at 230kV, 345kV, 400kV or sometimes 500kV, where kV stands for thousand volts. In Britain, most of the National Grid operates at 275kV or 400kV.
But China's existing UHV systems mostly operate at 800kV, nearly twice as high, or even 1,000 kV in some cases.
Operating at extremely high voltages creates technical challenges as transformers, towers, cables and relays must run safely in a more demanding environment than normal.
Much of the early work on UHV systems was done by electrical engineering companies such as Siemens and ABB . However, SGCC has mastered the technology and says 90 percent of the engineering work has now been localised.
China's existing UHV lines have delivered more than 160 terrawatt-hours of electricity since they were commissioned, about the same as the annual consumption of the state of Ohio or half what Britain uses in a year.
The company says its UHV lines have successfully withstood extreme weather, including heat, cold and storms.
Now China wants to export that expertise to other developing and developed countries looking to build long-distance transmission lines or super-grids.
In February, a consortium led by SGCC won a 30-year concession to build and operate a 2,000-km (1,240-mile), 800kV UHV line in Brazil. The transmission system will carry power from the Belo Monte dam in northern Brazil to the major consumption centres in the southeast.
"The successful bid fully reflects the company's advantages in this area and will promote China's technology, equipment and experience on UHV transmission into Brazilian and other overseas markets," SGCC trumpeted in a statement ("SGCC won the bid of Brazil's Belo Monte Hydropower UHV Transmission Project", Feb. 11).
In the past, some policymakers have expressed concerns about linking up China's entire electricity network in one giant super-grid, fearing more interconnectedness would also increase the risk of nationwide power blackouts.
But according to SGCC, top officials, including Chinese Premier Li Keqiang, endorsed the UHV super-grid strategy at a meeting in April.
"The Premier's stance ended the argument of whether to construct UHV. The answer is YES and MORE. This year will be a golden era of approving and constructing lots of UHV projects."
In practice, not all these projects are likely to be approved. SGCC has had its plans scaled back before. But enough will go into construction in the next few years to transform China's electricity industry radically. (Editing by Dale Hudson)