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Siemens building HVDC transmission system with record capacity of 2,000 MW

Siemens is building power converter stations for a high-voltage direct current (HVDC) transmission system with a record capacity of 2 x 1,000 megawatts. Beginning in 2013, the new HVDC PLUS technology will transmit 2,000 MW as direct current over a distance of 65 kilometers underground.

This system, which is being partially funded by the EU, connects the French and Spanish grids between Baixas and Santa Llogaia. At present the two countries’ grids are linked only by low-capacity lines.

Power grids will have to be substantially upgraded throughout Europe before more renewable energy can be used, Siemens says. The Desertec power generation project (earlier post) for the climate-friendly production of electricity in the deserts of North Africa and the Middle East, in particular, will require high-performance electricity highways.

Alternating current is commonly used for overhead lines, but it isn’t suitable for transmitting high capacities over long distances underwater or underground. In non-overhead systems, losses would be very high due to the charging and discharging of the cable capacities. In an HVDC system, on the other hand, transmission losses are 30 to 40% lower than in a comparable three-phase alternating current transmission line.

By 2013, developers at Siemens Energy will have constructed a system that can transmit 1,000 MW through each of two cables. The power will be transmitted at the highest voltage possible for today’s cables: +/-320 kilovolts. The new HVDC PLUS power converter stations use VSC-MMC (voltage-sourced-converter in modular multilevel-converter configuration) technology, which is not only more flexible and robust than today’s systems, but also less prone to faults.

At the heart of the new system is a converter that uses insulated gate bipolar transistors (IGBTs), which are semiconductor devices that convert alternating current into direct current and vice-versa. The system is very flexible since IGBTs can be switched at any time, no matter how high the voltage. A reactive power exchange is possible between each power converter and the three-phase alternating current network, which helps to stabilize overloaded grids.

In addition, MMC technology causes few high-frequency faults, which diminish voltage quality, so there is no need for high frequency filters. The system also has a black start capability, which means the grid doesn’t require external assistance to gradually restart after a blackout. Another advantage of the system is that the energy converters don’t have to change their polarity if the direction of the transmission is reversed, thus reducing wear and tear.

A 1,000-MW HVDC cable was recently put into operation along a 260-kilometer underwater line between the Netherlands and the UK. The first HVDC system in VSC-MMC technology also recently commenced commercial operation: the HVDC Plus installation with the project name Transbay, likewise erected by Siemens Energy, transmits 400 MW of electrical output at a transmission voltage of ±200 kV with low losses and high energy efficiency via an 88-kilometer marine cable link from Pittsburg, California, to San Francisco.

HVDC systems are part of Siemens’ environmental portfolio, with which the company generated about €28 billion (US$41.6 billion) in sales in 2010.

Comments

HarveyD

This technology could soon evolve to the level required for future smart power grids. Nobody likes to see power lines on their farms, in towns and cities.

SJC

There is no reason AC lines can not be underground, the capacitance to ground can be dealt with for shorter runs, it was mainly the cost. It was said to cost 20% more to put transmission lines under ground, so they chose not to.

Arne

Sjc,

Nevertheless, power companies don't put power lines underground. Apparently because they have to compensate for reactive power every 20 km or so, which costs energy, increasing the losses.

Arne

I mean 'AC powerlines', of course.

CelsoS


Choosing High Voltage Direct Current(HVDC) transmission lines for low loss or coupling of different frequency systems is not really something new. Just take a look at this http://en.wikipedia.org/wiki/HVDC_Itaipu !

    "Technical description

    High Voltage Direct Current (HVDC) was chosen both because this technique allows long transmission lines with little loss compared to other systems (like AC), and also allows interchange of the Paraguayan 50 Hz input and the Brazilian 60 Hz input and user grid. Both lines operate at ±600 kV and are built as overhead lines with a length of 818 (North line) and 807 (South line) kilometer. Away from their terminal stations, the two lines are at least 10 km apart to reduce risks. Each one is designed for 3150 MW at ± 600 kV D.C. and 2625 A. The lines are 4 x 689 mm² (about 30 mm ∅) ACSR cables.[2]

    Incoming is 500 kV AC from the hydro dam (Foz do Iguacu), outgoing is 345 and 500 kV AC into the South/Southeastern grid (Ibiúna, São Paulo). At 1/3 into the route, at Ivaiporã (Parana), there is a branch into 500 kV, 60 Hz AC, delivering into the Southern grid.

    By introducing, in 1989 and later, series capacitors in Ivaiporã (at ⅓ of the line) and Itaberá (at ⅔) the capacity grew from 4300 MW to 6300 MW."

SJC

Imagine if AC line were underground throughout the U.S. No more wind storm power outages due to lines being knocked down. When you look at what it costs to put them back up and the loss of power inconvenience, the extra cost seems like not so much of a burden.

Reel$$

SJC!! What a remarkable vision! And YES it is going to happen. But burying power lines has more than line loss and initial cost to be concerned about. There are costly easments and right of way issues. General maintenance is higher even than overhead because you have to dig the ground up to get at damaged sections.

The REEL solution is of course DISTRIBUTED ENERGY SYSTEMS - and it looks like the cat simply cannot be kept in the bag any longer.

Andrea Rossi's recent introduction of a catalyst that produces excess heat is likely to lead the way in the exotic area of LENR "The E-Cat produced 12.4 kilowatts of heat with an input of just 0.4 kilowatts, a gain of 31 times input power."

But there are LOTS of people and laboratories with similar results (Randy Mills, SPAWAR.) There IS a need for massive HVDC connectivity between large segments of grids. But the demand for these will be vertical as DISTRIBUTED ENERGY SYSTEMS replace outdated central power plants and grids.

This is going to be disruptive. But then, so was penicillin to strep. And the motorcar to livery stables. Change is good.

SJC

Distributed is fine and underground utilities will not stop that. There may come a time when distributed is the main source and the grid is the backup.

The one thing I know is I watch the news and there is a storm and it knocks trees down and the trees bring the lines down and many are out of power for days and all of this could be prevented easily.

Reel$$

Interested to hear from the engineers here. Large scale central power systems (traditional plus wind/solar transmitted across distance) or modular, self-contained energy distributed throughout communities?

Mr. Rossi is putting the heat on...

3PeaceSweet

There is no reason it can't be a bit of both. Large powerplants have a lot of benefits in economies of scale, but distributed CHP is a great fit for place that use lots of heat.

Although I do like the idea of being able to transmit electricity from Iceland to the UK

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