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Three Gorges - Changzhou China Converter transformers are 9th world's largest HVDC.

With support from The Three Gorges Office of the State Council, National Development and Reform Commission and State Grid Corporation, a combination formed by our company and ABB Corporation designed and submitted a bid jointly for Three Gorges — Shanghai DC Transmission Project (?500kv,3000a,3000mw); the XD Transformer Co., Ltd. of the XD Group has obtained manufacture task of 14 converter transformers and 3 smoothing reactors, and the quantities of machines it made are much more than the quantities it made in Three Gorges — Guangdong DC Transmission Project. Significant breakthrough has been made in localization of manufacture of thyristor valve, system research and design of complete set of equipment of converter station: a combination formed by our company and ABB Corporation designed and submitted a bid jointly, 50% thyristor valve used in the project, i.e. twelve lockshield valves, were made by XPR of our company, and thyristor components(348 components totally)of another 50% thyristor valves were also assembled by XPR XIHARI(Xi'an High Voltage Apparatus Research Institute Co., Ltd.)of the company has undertaken system research and design of complete set of equipment of the converter station of the project together with Beijing Wanglian DC Engineering Technology Co., Ltd. Total amount of the contract is USD 114.877 million, which is equivalent to RMB 949.34352 million Yuan according to list price of exchange rate 1: 8.264 of Bank of China on June 16, 2004. 

China XD Group’s ability on technology and manufacture of DC transmission has taken three steps through the engineering practice of four 500kv DC Transmission Projects of Three Gorges-Changzhou, Three Gorges-Guangdong, Guizhou-Guangdong and Three Gorges-Shanghai:

  • We introduced technology; assembled and manufactured some equipment when we took part in Three Gorges-Changzhou Project;
  • We jointly designed and independently manufactured converter transformers and smoothing reactors in Three Gorges-Guangdong Project and Guizhou-Guangdong Project.
  • We have made the depth of localization and manufacture share of domestic manufacturing company taking a step by adopting the ways of joint-design, syndicated tender and independent manufacture in Three Gorges-Shanghai Project, especially the significant breakthrough we made in the aspects of localization of making thyristor valve and system research and design of complete set of equipment of converter station.

Therefore, China XD Group has the ability of designing and manufacturing and supplying converter transformer, smoothing reactor and thyristor valve used in ?500kv HVDC Transmission Project; has two programs for transporting converter transformer and smoothing reactor by rail and by road; can take part in or undertake system research and design of complete system of converter station of ?500kv HVDC Transmission Project.

Source: China XD Group


Guizhou – Guangdong, China converter station is top 10 largest HVDC line in the world. 

The DC Transmission Project (the long-distance transmission system of the Guizhou-Guangdong II line ± 500 kV) transmits 3,000 MW power from the Xingren substation in the Guizhou Province of Southwest China to the load center of Shenzhen in the Guangdong Province.

The system has a long-term overload capability of up to 115 %. Power transmission in the reverse direction is also possible. The project is carried out in cooperation with Chinese partners supported by Siemens. The bipolar system is designed for a ceiling suspended 12-pulse converter bridge arrangement with single-phase two-winding converter transformers and oil-insulated smoothing reactors.

The 500 kV DC converter groups of modular design are equipped with direct light-triggered thyristors with water cooling. Most of the DC equipment is provided with composite housings improving the performance of operation under severe environmental conditions.

For harmonic filtering triple tuned AC and DC filters are used. The design considers the installation at 1450 m above sea level (Xingren converter station). The interconnection of the neutrals of both stations is implemented by means of ground electrodes. The contract was awarded in May 2005.

After successful completion of the test phase, Siemens Energy commissioned the “Guizhou-Guangdong II” high voltage DC transmission link (HVDC) on schedule at the beginning of January 2008.

source: Siemens


HVDC facilitates the movement of electric power from resource-rich areas to faraway demand centers. This is an existential boon for intermittent power generation resources, such as wind and solar, since HVDC can average out and smooth the outputs of large numbers of geographically dispersed wind farms and solar farms.

In fact, studies have shown that an HVDC-based wide area super grid covering the fringes of Europe can bring 100% renewable power to the continent at close to today’s prices.

But in the age of Trade Wars, it has become more and more critical to tap both public and private financing to cover the costs of building and operating HVDC energy highways, including China’s $250 billion upgrade plan to link regional grids via 20 HVDC power corridors by 2020.

The power sector now attracts more investment than oil and gas combined, and this opportunity to define the future of energy will certainly make the difference between which power companies and electrical equipment providers grow into new markets and which ones are gobbled up in mergers and acquisitions.

Having the world’s largest electricity market nearly double the size of the United States’ at 6.3 million GWh per year, the economy driving much of the growth in the power sector will be China’s. 

Motor systems used in Chinese industry alone will account for almost a fifth of the increase in global electricity demand to 2040, and home air conditioners in developing economies like China are increasing to 2.5 billion units, up from 600 million today.

Wouldn't you benefit from strong relationships with the dominant transmission system operators of the world’s largest and fastest-growing electricity markets — minus political noise?

When you attend the 3rd Annual HVDC Energy Highways Conference, you not only gain new connections for partnership with the transmission system operators from around the world who are investing in HVDC technology but also with public and private sources of financing looking to support infrastructure development in the world’s fastest-growing economies.

Registration is EASY! Simply complete your delegates' details on the Registration Form, include your card details, and send it back to This email address is being protected from spambots. You need JavaScript enabled to view it.!

Group discounts are available for teams of 3 and 5.


"Well-organized conference!"

- Jim Cai, Director, State Grid NA


"High-value content for HVDC!"

- Jesús Martos, Director, Siemens


Beyond the ‘break-even’ distance, HVDC transmission systems cost less, even with the added expense of terminal stations. Meanwhile, an HVDC line has lower power losses than an HVAC of the same capacity in practically all cases, which means more power is reaching its final destination.

HVDC systems also have a lower environmental impact because they require fewer overhead lines to deliver the same amount of power as HVAC systems. And HVDC interconnections enable power systems to use generating plants more efficiently, for example substituting thermal generation with available hydropower resources. 

The technology is a key component in the future energy system based on renewable energy sources, such as wind and solar power which are often both volatile and remotely located.


Positive effects on the power systems

Many HVDC transmissions have been built to interconnect different power systems. The links help existing generating plants tied into a power system operate more effectively, so new power station builds can be deferred. This makes economic as well as environmental sense.

The obvious environmental benefit is not having to build a new power station, but there are even greater gains coming from the operation of an interconnected power system that uses its available generating plants more efficiently. There are great environmental advantages to linking a power system with large hydroelectric resources to a system with mostly thermal generation. You can reduce thermal generation (predominately at peak demand) by tapping the hydro generation, which also helps to run the thermal generation more efficiently at constant output, without having to follow load variations.


Reduced right-of-way

One bipolar HVDC overhead line is comparable to a double circuit AC line from a reliability point of view. Therefore, a single HVDC line with two conductor bundles has less environmental impact than a double circuit AC line with six conductor bundles - it requires less space and has less visual impact.

With HVDC Light it is possible to use extruded polymer cables for DC transmission. This has made the use of buried land cables an interesting alternative to traditional overhead lines.


Lower losses

HVDC transmission losses are lower than AC transmission losses in practically all cases. An optimized HVDC power transmission line has lower losses than AC lines of the same capacity. Losses in the converter stations must also be added and they are about 0.6 percent for HVDC Classic and below 1 percent for HVDC Light of the transmitted power in each station.

Hence, in a side-by-side comparison, total HVDC transmission losses are still lower than the AC losses in practically all cases. HVDC cables also have lower losses than AC cables. The diagram below shows a comparison of the losses in 1,200 MW overhead line transmissions using AC and HVDC.

Losses overhead line AC versus DC


Lower investment cost

An HVDC transmission line costs less than an AC line for the same transmission capacity. However, it is also true that HVDC terminal stations are more expensive due to the fact that they must perform the conversion from AC to DC, and DC to AC. But over a certain distance, the so called "break-even distance" (approx. 600 – 800 km), the HVDC alternative will always provide the lowest cost.

The break-even-distance is much smaller for subsea cables (typically about 50 km) than for an overhead line transmission. The distance depends on several factors (both for lines and cables) and an analysis must be made for each individual case.

The break-even distance concept is important, but only one of a number of factors, such as controllability, that are important to consider in choosing an AC or HVDC transmission system. 

source: ABB



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