China, India, SE Asia to spend billions constructing, upgrading transmission systems
A new generation of UHV transmission systems and environmentally friendly structures are now being specified
By H. (Tod) Kennedy
Asia Pacific Editor
As power station construction proliferates, especially in the emerging industrial countries of Asia, remote populated areas, by necessity, are being linked by high-voltage (HV) transmission lines–like highways connecting cities often separated by harsh terrain, rivers, seas or political boundaries. With the integration of networks inside and outside national borders, many countries are fast restructuring their electricity transmission policies and looking for new approaches to tower construction, ultra high-voltage (UHV) lines and environmental options such as green, slim-profile structures and economic burial of HV cable.
In Asia, the China National Power Corp. plans to install 9,100 km of 500 kV transmission line and 24.75 million kVA substation capacity as a key part of the massive Three Gorges Grid Project to integrate regional and provincial power grids. To meet its rural needs and export electrical power to Thailand, Laos has plans to expand its transmission system fivefold by the year 2000.
Plans are under way to construct 560 km of undersea transmission cable to transfer power from the huge Bakun hydroelectric project in East Malaysia with the booming industrial peninsula of Malaysia across the South China Sea. In addition, Malaysia is planning to spend (US) $3.7 billion by 1997 in upgrading its electricity grid system.
Australia, on the heels of corporatization and privatization, is working on establishing a national power grid. Currently, the state of Queensland is connected with New South Wales via a 400 km HV line which is part of the Eastlink network. Eventually the island state of Tasmania, known for its sizable hydroelectric capacity, is expected to be connected to the mainland by an undersea cable.
Along with the global privatization and unbundling of electrical power, we see parallel advances in technology from tower design, safe cabling and solid state substation controls to single-mode, fiber-optic communication lines.
According to Pierre Daures, Electricité de France (EdF) CEO, EdF has a program to expand and improve its power grid. Currently, it takes five to six years to permit, design and construct new transmission lines, said Daures. However, to meet the need for upgrading and expanding its transmission system, EdF will construct new transmission lines, renovate obsolete sections and bury some of its older overhead lines.
Because of environmental concerns, EdF has taken steps to provide green transmission masts, camouflage some substation facilities and bury HV and low-voltage (LV) cables where practicable. However, said Daures, “An LV or medium-voltage line buried in a rural or suburban area costs one to three times more than an overhead line–and for an HV line, three to five times more.”
Despite the cost constraints, EdF has buried 21 percent of its medium-voltage lines, while for HV lines, the burying rate is set to increase from 5 to 10 percent. Plans call for burying 100 km of new HV cable each year. The French consider it virtually impossible, with today`s technology, to operate a very HV grid underground. Currently, it is only feasible to bury these cables in the immediate area surrounding nuclear power plants and outskirts of major metropolitan areas. EdF says a buried 400 kV line costs 20 times as much as an overhead line, and its operability is uncertain.
It is estimated that between now and the year 2015, 4,400 km of 400 kV supplementary double lines must be built, of which 2,000 km is to replace single lines. This means the net increase in routing will be 2,400 km, or 120 km annually. The French are literally going green with their power transmission towers and poles, and they`re looking for more aesthetic structures. While the angled trellis pylon enjoyed its days of glory, EdF is changing to structures which integrate better with the countryside. The Trianon pylon now being utilized was designed with a lower silhouette. This pylon owes its design to its first application–the axis of the Versailles Palace and the Trianon. Concurrently, the Apollone pylon, erected on a 225 kV line near Mantes, received the French industrial aesthetics award.
In the 1970s, the company asked a jury of independent experts to choose among six trellis pylon models, judge them on their aesthetic qualities and determine the materials best suited for the structure. This brought about the birth of the Beaubourg pylon. With its slender silhouette, it is considered a milestone in the evolution of transmission line pylons. In the 1980s, EdF took an interest in the US monopodal, tubular form, and the competition winners prototype designs built along these lines were recently installed. By the year 2000, some of these newer type aesthetic pylons will be installed. In addition, EdF is introducing a glued-laminated wooden structure called the Corolle pylon. This will be used for lines up to 90 kV. The first Corolle pylon is being installed in eastern France. EdF lines and poles are color coordinated according to the landscape. For example, in the Alps some lines are painted in shades of gray, while in the city, pylons are often painted in vibrant colors to blend with urban buildings.
As for the future of VHV underground cabling, despite the odds, the French are persisting with research. This includes the design of huge capacity dispensing and trenching machines which are designed to reduce installation costs by 10 percent. Two major research and development projects have been progressing since 1993, focusing on two types of cable–synthetic insulation cables with high transmission capacity and nitrogen gas insulation cables. In theory, this will increase transmission distances up to 200 km.
UHV for China
The great leap forward in the economy of China has led to urgent demands, nationwide, on the electric power industry. In addition, with the construction of the Three Gorges Dam hydroelectric scheme, the country is confronted with the need to rapidly expand its transmission network with modern technology and the ability to carry UHVs across vast areas.
According to Mr. Wang Weilin, Ministry of Electric Power Wuhan High-Voltage Research Institute chief engineer, the country is aiming for a 1 million voltage transmission system. This would be similar to the 1,150 kV system his team inspected in the former Soviet Union and the 1,000 kV double-line, single-tower transmission in Japan. The latter links several nuclear power stations with a loop network of 500 kV around the Tokyo, Japan, area.
“We developed 330 kV transmission lines in the 1970s and the 500 kV level in the 1980s. However, now it is time to develop the 1,000 kV voltage grade,” said Mr. Wang. China`s electricity load center is located in the economically developed southeast, while hydropower resources are located in the southwest of China. China`s coal and oil resources are located in the north and southwest parts of the country and as a consequence require electricity to be transferred from west to east and from north to south, at a HV and large capacity.
The Three Gorges Power Station, located in central China, will be the largest of its kind in the world. It is set to have the first group of units in operation by the year 2003 and all 26 running by 2010, providing a minimum capacity of 18,200 MW. If the Gezhouba hydropower station, which is 40 km away from the Three Gorges, is included, the total capacity of the two stations will be 25,115 MW, according to Mr. Wang.
The transmission lines from these power plants will first be connected to the Central China and East China networks, and later to the country`s northern and southern networks. The objective is to form a national grid. To ensure the economic and consistent operation of all networks, complementing hydro and thermal power, a 1 million voltage united frame network is to be established. It will be centered around the Three Gorges Power Station and be a regional 500 kV network. If necessary, it can be connected with the 500 and 600 kV dc lines.
Plans call for the immediate construction of nine transmission lines on the left bank of the Three Gorges project and 13 transmission lines on the right bank. Mr. Wang said that according to former Soviet Union experience, although the cost of one 1,150 kV transmission line is about equal to four 500 kV lines, the capacity is almost equal to five 500 kV lines.
“If we build one or two million voltage transmission lines, of 1,000 kV to 1,200 kV, the number of 500 kV lines will be greatly reduced and the problems associated with the transmission corridor will be solved,” he said. “Three Gorges can supply electricity with 500 kV lines directly to Hubei, Hunan, Henan and east Sichuan, and with 1,200 kV transmission lines via Wuhan, Anhui (Jiangsu) to Shanghai on the eastern route, and via Dhuengqing to Yalongjiang Ertan hydropower station on the western route, covering a direct distance of 1,500 km from east to west.”
This will link 11 key power stations having a total capacity of 47,380 MW. Some of these plans are still under construction but should be completed by the year 2020 at the latest. Said Mr. Wang, “It takes 15 to 20 years to accept and construct a new voltage line. This includes basic research, model trial production, engineering design, equipment manufacture, construction, testing and operation.”
With UHV entrenched in the Chinese plans, the Ministry of Electric Power has instituted formal research on the subject. The ministry`s 1,000 kV models will be based on China`s 500 kV experiences and current UHV systems. Utilizing this information, a proposal for forming a special organization and raising funds has been submitted to the Chinese government.
“The new technology on UHV transmission will push our country`s electric power industry and electrical manufacturing industry into a new stage,” said Mr. Wang.
The Chinese have inspected HV transmission line constructions in several countries. These countries have adopted traditional lines with “V” style pendants, having three-phase lines framed in the tower window and insulation sticks between two phases. However, for HV, high-power compact lines, they prefer optimum-range divided conductors in every phase to enlarge the maximum field intensity to the upper limit. Because the line capacitance is increased and line impedance is reduced, the transmitted power is increased greatly. The HV, high-power compact line also decreases the tower`s weight and narrows the line passage.
Currently, Chinese researchers are carrying out trial tests on 220 kV lines in China. New technology, with different tower material, insulation sticks are being tested on lines up to 500 kV. Information from these tests will be used in designing the future 1,000 kV transmission lines.
According to Mr. Wang, China has adopted fixed-bound, parallel reactance and static compensation devices in its 500 kV and 330 kV power systems. However, these are not suitable for the 1,000 kV systems because of larger voltage drops at higher loads. To overcome this, China has developed a controlled reactance which has the ability to limit operation over-voltage and separately serve as a reactive power compensator. China believes that this kind of controlled reactance should be developed rapidly from LV low capability to HV high capability, he said.
Parallel with the new technology used for the towers and conductors, the Chinese are looking at using state-of-the-art remote control systems for unattended substations and improved transformer equipment. Mr. Wang said that new equipment and methods to improve efficiency should be introduced, including infrared cameras, infrared temperature measurement technology, laser distance measurement equipment, small style helicopter patrols and operating robotics.
In tune with worldwide trends, India has established a central agency called the Power Grid Corporation of India (Powergrid). Its task will be to monitor, mediate and coordinate the country`s multiplicity of state power authorities and joint ventures and ensure integration of regional grids, while acting as a pooling body for all the transmission lines and substations under a nodal transmission structure (see figure).
Powergrid has the enormous task of establishing grid discipline, which will be helped by enhancing the role of Regional Electricity Boards and augmenting the regional grids. Ultimately, they will be integrated into a national grid system. The goal is to improve the operation and maintenance of its transmission systems, strengthen regional power grids and establish inter-regional links. India is also introducing a rationalized tariff structure for exchange of power between states and five of the country`s regions which are now operated by Powergrid. According to a study, inter-regional links will save about 10,000 MW of generation capacity after the year 2000. Because of this, India is expected to see a reduction of unserved demand by 50 percent over the next few years.
The World Bank has extended a loan of (US)$350 million to Powergrid for various projects and organizational studies. It has also committed up to (US)$1.5 billion for other power-related projects. Currently, there are 19,092 km of 400 kV ac lines and 1,630 km of HV dc systems in operation. India is also constructing 132, 200, 400, 800 kV systems, along with 13 substations. Total installed transmission capacity is 22,750 MVA distributed over 53 substations throughout the country.
According to Powergrid executives, they are committed to adopt the most modern technologies in power transmission. To do this they are implementing an 800 kV transmission system which will help them transfer large blocks of power, conserve rights-of-way and reduce the costs for upgrading and uprating existing systems.
Other technological areas of crucial importance include:
– unified load dispatch and communication facilities;
– HV dc back-to-back system;
– large capacity, long distance HV dc bipole;
– series compensation and static VAR compensation to existing lines; and
– phase shifting transformers to adjust flow of power in parallel circuits and improve the transient and dynamic performance of the system.
The corporation, in keeping with India`s “open economy” has signed a memorandum of understanding (MOU) with the National Grid Company PLC in the UK for exchange of information and expertise. It has also signed an MOU with Hydro-Qu?bec International of Canada for sharing experience and technological cooperation in the field of power system engineering and joint business development.
Powergrid`s long-term perspective is to become a “facilitator-cum-change agent” in restructuring the Indian power sector. This will be performed through its various business divisions, some of which will promote regional power pools. The corporation envisions the concept of “joint network operator” with state electricity boards (SEBs) for integrated regional system planning. Under this concept, SEBs will remain responsible for their investments and would own, maintain and operate their own lines and substations, while Powergrid`s role would evolve as a facilitator for scheduling, dispatching and settlement services.
Transmission and distribution (T&D) systems are receiving priority treatment according to the Ragyadhyaksha Committee of Power, which recommended that the allocation of expenditure for generation, T&D and rural electrification should be a ratio of 4-to-2-to-1. In other words, T&D should get up to 50 percent of the total allocation of resources for the power sector. This is in a climate where frequent power cuts, load shedding, grid collapses and continuous voltage fluctuations have become a common feature in most parts of the country.
Because of the inability of Indian utilities to keep pace with T&D development, a new effort is being made to encourage private investment in this field. And already, states such as Orissa, Rajasthan, Haryana and Uttar Pradesh have initiated structural reforms to attract international funding for both generation and transmission work.
Australia and SE Asia
Australia has some of the world`s largest facilities for the manufacture and testing of transmission towers, poles and conductors. A leading company in the business, Transfield manufactures and installs transmission lines throughout the Asia Pacific region. Today, the company is also involved in the construction of thermal and hydropower generation plants. One of its divisions, Transfield Transmission Lines, has designed and built more than 50 HV systems in Australia, Thailand and Malaysia.
In 1995, the company started its second contract in Sarawak, Malaysia, for the supply and installation of a 132 kV transmission line. Under this contract, the company is responsible for the design, fabrication, testing and erection of all structures, including 100 m-high river crossing towers. It is supplying and installing control and communication systems utilizing fiber-optic cable.
With the development of independent power producers in Malaysia, the demand for 500 kV transmission lines will continue. Plans are under way for the installation of an undersea cable link across the South China Sea. The first section of the line, linking Johore, at the southern tip of the peninsula to the Thai border in the north, has just been completed. A contract for the second stage will soon be put out for bid.
Structural testing system used for HV transmission tower analysis. Photo courtesy of Transfield, Australia.
Tower test rig operated by Transfield in Sydney, Australia. Photo courtesy of Transfield, Australia.
220 kV transmission line across the Yarra River, Victoria, Australia. Photo courtesy of Transfield, Australia.
A ccording to Dean Caletti, of Transfield Transmission Lines, the company was the first in Australia to build a full-scale test facility for high-voltage transmission towers.
This equipment, located at Seven Hills, Sydney, Australia, simulates wind forces on the tower and conductors, as well as loads induced by conductor tensions.
Verification of existing structures or designs can be carried out promptly and accurately in the form of design checks or a full-scale tower test. One of the computerized programs developed by the company is “Trantower,” which is used in for the design of lattice tower structures fabricated from steel angle sections.
The testing facility requires the application of loads on the structure to simulate, as near as possible, the actual loads encountered when the transmission line is in service. Loads are applied in the transverse, longitudinal and vertical directions to model the conductor and wind effects on the structure.
The facility is designed to test three basic structures–pyramidal, delta and pole–under critical load conditions. All of the loads applied to the structures are continuously monitored. In addition, a control system is used to simultaneously load and/or unload the structure under test.