[LINK] Back of Beyond Power Transmission Costs and Efficiencies.

Tue Apr 5 09:24:31 AEST 2011

I do admit that Australia has more distance to cover than most countries but a couple of things you've said don't add up.  

The total transmission power loss for the whole of the US which has a huge grid and an area similar to Australia was 6.5%.  From Innamincka they only have to get to the nearest point on the grid, not to Victoria.  That might be Broken Hill 350km or Roxby Downs 300km or at the furthest Adelaide 550km?  

>From the (secure) wikipage:
> Losses
> 
> Transmitting electricity at high voltage reduces the fraction of energy lost to resistance. For a given amount of power, a higher voltage reduces the current and thus the resistive losses in the conductor. For example, raising the voltage by a factor of 10 reduces the current by a corresponding factor of 10 and therefore the I2R losses by a factor of 100, provided the same sized conductors are used in both cases. Even if the conductor size (cross-sectional area) is reduced 10-fold to match the lower current the I2R losses are still reduced 10-fold. Long distance transmission is typically done with overhead lines at voltages of 115 to 1,200 kV. At extremely high voltages, more than 2 MV between conductor and ground, corona discharge losses are so large that they can offset the lower resistance loss in the line conductors. Measures to reduce corona losses include conductors having large diameter; often hollow to save weight, [8], or bundles of two or more conductors.

I don't see why upping the voltage to 1.2Mv would be so costly and anyway that's a part of the capital cost of the project that can be written off over a very long time?  In any case there are a few industrial/mining projects in the area that can use some of the power saving what they are now taking off the grid.

On 2011/Apr/05, at 8:18 AM, Tom Koltai wrote:

> In response to Greg Kim and Andy...
> 
> OK, here goes.... (difficult to do within the restrictions imposed on an
> ASCII text based transmission medium ...)
> 
> On further reading, the hotrocks project will in fact be a 50 MW plant
> so the 2 MW dissipating to zero by Melbourne doesn't apply.[5]
> 
> For the other Linkers scratching their heads about power loss...  
> 
> Start Prologue/
> The cost of delivering 50 MW of power from the Hotrocks project to
> Portland Victoria, with less than 2% power loss  (direct) would be
> approximately 1.2 billion dollars Therefore unrealistic and commercially
> unviable.
> /end prologue
> Disclaimer - There are many factors involved, right of way, terrain,
> temperature variations along the transmission lines, wind shear [HV
> cables swinging in the wind] , therefore this  number should definitely
> be discounted as a back of the envelope stochastically generated A--e
> Pl--k.
> ================================
> 
> In simple terms, higher amounts of power can be transmitted if
> transmission voltages are higher. [2]
> 
> The majority of Australia's Grid (was in 2004) at 330 kV (that's 330,000
> volts).
> 
> Let us say that the power in Innamincka will be generated at 23000
> Volts, it then needs to stepped up to 330 kV for the long haul in
> between transgrid points, when it leaves the Grid network, it is
> transformed down to 132 kV and then after distribution to the regional
> substation it is transformed again down to 33 kV and when it gets to the
> city substation it is transformed again to 11 kV and sent around to the
> transformers you see on poles in the street, these transformers then
> transform the power one more time down to 415 V for reticulation to you,
> the user.
> http://kovtr.com/data/Key_Elements_of_the_Grid.gif
> 
> 
> Now we need to analyse the power loss at each of these Voltages.
> 
> 6.6 kV     PLP km  278%
> 11 kV      PLP km  100% 
> 20 kV      PLP km    30%
> 33 kV      PLP km    11%
> Source [1]
> 
> PLP = Power Loss Per 
> 
> Australia is upgrading her transmission Grid gradually. But it is a
> hodgepodge of different transmission voltages.
> 
> 345 kV    PLP 200 km       8%
> 500 kV    PLP 200 km       2%
> 765 kV    PLP 200 km     <1%
> http://kovtr.com/data/Graph_Relative_line_losses_for_various_transmissio
> n_voltages.gif
> 
> Unfortunately the cost of a substation to step up the power to 765,000
> volts (for a 50 mW plant is close to 50 million dollars.) and the cost
> of the transmission line exceeds 1 million per kilometre. 
> 
> Quote/ [Ref: Table 3. Typical Capital Costs for Electric Transmission
> Lines, by Voltage [4]]
> New 345 kilovolt (kV) single circuit line $915,000 per mile
> New 345 kV double circuit line $1.71 million per mile
> New 138 kV single circuit line $390,000 per mile
> New 138 kV double circuit line $540,000 per mile
> New 69 kV single circuit line $285,000 per mile
> New 69 kV double circuit line $380,000 per mile
> Single circuit underground lines Approximately four times the cost of
> aboveground single circuit lines.
> /Quote
> Source: American Transmission Company, 10-Year Transmission Assessment,
> September 2003.
> 
> Quote/  [4]
> In a recent proposal to build 34 miles of 500 kV in California, the "per
> mile" cost of the project was $10 million.
> /Quote
> 
> Therefore as can be seen from the brief insight that I have tried to
> give, Transmission losses vary depending on the voltage, the feeder
> length, the number of interconnects into the feeders and the
> interconnects into the transmission long hauls.
> 
> In Australia, in 2005 based on the Grid as it was then constructed and
> all of the information that I compiled over four months [incomplete for
> parts of South Australia and northern QLD] [remembering that NT and WA
> are not part of our eastern seaboard power grid] and analysed over three
> weeks of mind numbing excel data comparison modelling...
> 
> The transmission loss was 2 kW per kilometre and I will defend that to
> my grave.
> Of course, with the Grid constantly being upgraded and with new
> consumers [read Greenfield developments] and decreasing industrial
> requirements, that 2 kW figure today may have changed by as much as 5%
> to 2.1 kW or maybe down to 1.9 kW.
> 
> ("And sometimes I should just shut-up and not say anything", he says
> after an hour of compiling this stuff....)
> 
> References:
> 
> [1] Electricity distribution network design Page 168 Table 9.1 Relative
> Characteristics of medium-voltage overhead lines. [ E. Lakervi, E. J.
> Holmes]
> http://books.google.com.au/books?id=HMLBEXay1DUC&pg=PA168&lpg=PA168&dq=R
> elative+line+losses+for+various+transmission+voltages&source=bl&ots=x2vF
> YxkjVS&sig=BSqbWkXSUk_rxZFNbVBvwdZ8p3Y&hl=en&ei=6SOaTdzXBY66vQPQ5IDkCw&s
> a=X&oi=book_result&ct=result&resnum=7&ved=0CEEQ6AEwBg#v=onepage&q&f=fals
> e
> [2]  Practical Concepts in Capability and Performance of Transmission
> Lines [CLAIR 1953.]
> http://www.nerc.com/docs/pc/spctf/Practical_Concepts_in_Capability_and_P
> erformance.pdf
> [3] http://www.aep.com/about/transmission/docs/EnablerforCleanEnergy.pdf
> [4] Electricity Transmission - A Primer
> http://www.raponline.org/Pubs/ELECTRICITYTRANSMISSION.pdf
> [5] http://www.geodynamics.com.au/IRM/Company/ShowPage.aspx?CPID=1464
> (Rename to Showpage.pdf - stupid IE format closed eco system Microsoft
> web servers - should all be crushed and remanufactured as iPads..)
> 
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> Link mailing list
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