HVDC systems
Modern HVDC systems combines the good experience of the old installations with recently developed technologies and materials. The result is a very competitive, flexible and efficient way of transmitting electrical energy with a very low environmental impact.
It is important to remark that an HVDC system not only transmit electrical power from one point to another, but it also has a lot of value added which should have been necessary to solve by another means in the case of using a conventional AC transmission.
Ok, here are the three really awesome high-voltage direct current (HVDC) transmission projects finished in last ten years in Australia:
1. Basslink
Crossing Bass Strait required a submarine cable measuring 290km in length, which now is the longest of its kind in the world. The charging current of such a cable makes a High Voltage Alternating Current (HVAC) solution impossible, and therefore High Voltage Direct Current (HVDC) transmission was the only feasible solution.
The Basslink HVDC Interconnector consists of a monopolar metallic return scheme, with a rated DC voltage of 400 kV, a rated DC current of 1250 A and a rated continuous power of 500 MW defined at the DC terminal of the rectifier converter station. Both HVDC converter stations, located at Loy Yang (Victoria) and George Town (Tasmania), are designed to transmit rated power in either direction.
Additionally, the HVDC system has a dynamic power transfer capacity of up to 630 MW from Tasmania to Victoria to meet Victorian peak demands.
Under fault conditions the HVDC frequency controller can rapidly control DC power to prevent frequency deviation beyond a certain limit.
Project Details
| Project type | HVDC interconnector |
| Location | Bass Strait, between Victoria and Tasmania Converter stations at Loy Yang (Victoria) and Georgetown (Tasmania) |
| Capacity | – 400 kV DC transmission – 12 pulse bridge line commutated HVDC – 60 thyristors per valve, 720 total per station – 500 MW continuous rating. Dynamic facility for limited time of up to 6 hours for 630 MW |
| Year of commissioning | 2006 |
| Purpose | To connect the 500 kV transmission system in Victoria and the 220 kV transmission system in Tasmania, at 290 km in length, Basslink is the world’s second longest submarine power cable |
Video // Basslink, The National Grid
2. Directlink HVDC Light Project
Terranora interconnector is a 180 MW underground HVDC Light transmission link connecting the New South Wales and Queensland electrical grids in Australia, allowing power to be traded between the two states.
The 65-km long link was built by TransÉnergie Australia, a subsidiary of the Canadian utility Hydro Québec and Country Energy. TransÉnergie US supplied its technical expertise for the construction and operation of the interconnection, as well as its expertise in marketing transmission services.
| Project type | HVDC interconnector |
| Location | Between New South Wales and Queensland, with converter stations at Bungalora (New South Wales) and Mullumbimby (Queensland) |
| Capacity | Main data Rated power: 3×60 MW DC voltage: ± 80 kV DC current: 342 A per converter AC system voltage Bungalora 110 kV Mullumbimby 132 kV AC filters (per converter): 39th harmonic 1 branch 78th harmonic 1 branch IGBT valves Valve type: two level Cooling system: water IGBT type: 2.5 kV/500 A |
| Year of commissioning | 2000 |
| Purpose | An HVDC Light™ project to connect the New South Wales and Queensland electricity grids and to boost supply services to the Tweed Heads region of New South Wales |
3. Murraylink HVDC Light Interconnection
The Murraylink 220 MW ±150 kV HVDC Light bipolar interconnector is believed to be the world’s longest underground power transmission system, connecting the Riverland region in South Australia and Sunraysia region in Victoria through converter stations at Red Cliffs in Victoria and Berri in South Australia.
The controllable interconnection allows power to be traded in either direction between the two States, and provides enough electricity to meet the needs of around 200,000 households. ABB’s HVDC Light transmission system comprises extruded (oil free) cables buried in the ground and an HVDC Light converter station at each end of the link.
Key reasons for the choice of voltage source converter (VSC)-based HVDC technology include:
- Buried cables, enabling use of existing rights-of-way and speeding up the permit/approval process;
- Reactive power control to support weak AC networks;
- Compact converter station layout, and
- Modular, factory-tested design for a short field testing and commissioning period.
The Murraylink project earned several Australian state and national awards for both environmental and engineering excellence.
| Project type | HVDC interconnector |
| Location | Between South Australia and Victoria, with converter stations at Berri (South Australia) and Red Cliffs (Victoria) |
| Capacity | Main data Rated power: 220 MW DC voltage: ± 150 kV DC current: 739 A AC system voltage Red Cliffs 220 kV Berri 132 kV Reactive support at rated power Inverter operation: -100 +100 MVAr Rectifier operation: -75 +125 MVAr IGBT valves Valve type: VSC 3 level IGBT type: 2.5 kV/1000 A Cooling system: water HVDC Light cables Cross section: 1200 and 1400 mm2, Aluminium Outer diameter: 80.2 and 83.7 mm Length: 2×176 km |
| Year of commissioning | 2002 |
| Purpose | An HVDC Light™ project, with converter stations at Red Cliffs in Victoria and Berri in South Australia, to connect the Riverland region of South Australia and the Sunraysia region of Victoria. At 176 km in length, Murraylink is the world’s longest underground high-voltage interconnection |
HVDC Light – invisible on the map
References:
- CIGRE – Enhancing the Transmission Networks
- Case Study: The Basslink HVDC Interconnector – SIEMENS
- High Voltage Direct Current (HVDC)Transmission Systems Technology Review Paper – Roberto Rudervall
- ABB Energiekabel GmbH
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