FYI: Northern Pass High Voltage Transmission Project

[Waumbek]

I am just getting wind of this project and do not find mention of it in a forum search. Nor do I know much about it yet other than the fact that the HV lines aim to transmit power from Quebec to NH/New England. There's a first public meeting on Monday in Sugar Hill and Franconia; presumably the company will pitch the project. Maps can be found at

http://www.northernpass.us/maps/Project Route_Map_101410.pdf

The "preferred route" in this area cuts right through the Rocks Estate (SPNHF) in Bethlehem and uses an existing ROW in the WMNF; it crosses the AT on the Kinsman Ridge between Mt Wolf and Eliza Brook shelter and goes down through the lower section of Franconia Notch (see pg. 2 of the pdf maps). The alternative route, not preferred by the company, takes the line west of the WMNF and Franconia Notch and then heads east again lower down through the Plymouth area, thus bypassing the Notch area. This alternate would be roughly along the old rail route "bypass" into the north country.

Is it feasible, technologically and economically, to bury these lines in sensitive areas?

 

[MichaelJ]

That appears to be exactly the route of the existing power line corridor, at least from 302 Bethlehem through Rocks, Sugar Hill, over Kinsman ridge, and down past 112, so I'm not sure what impact there would be.

A neat idea, to take a high-voltage DC line from Hydro Quebec right down into Southern NH to feed the grid. Environmentally, however, I have no idea.

 

[Lou Hale]

Burying lines is very expensive I think the last person I talked to said 10X the cost but that's as un official as estimates get. I think its also way more intrusive to install and repair buried lines.

 

[Craig]

I'm not sure they can bury a 300KV transmission line. Those high voltage overhead transmission lines are steel – uninsulated cable. Additionally, those voltages put off a significant EMF. I wonder if the EMF would be too strong (for living things) at ground level.

<drift>
The original engineered plan for supplying 15KV power to MW Obs was to install conduit on the side of the cog trestle. There was to be separate conduit for the power and fiber optic cable. This was the most cost effective way to get power and communication to the summit. Unfortunately, the engineer couldn't demonstrate code compliance so that scenario was scrapped.

Eventually they engineered direct burial 15KV cable for power and buried conduit to install the fiber optic cable. This method was vastly more expensive (monitarily & enviromentally) but was code compliant and will probably last a lot longer than exposed conduit.
</drift>

I know they are developing direct submersion cable for the use in the distribution of offshore wind power. Not sure what voltages those will be rated for.

Hold on tight, you're going to see more and more above ground transmission projects in the future as we move away from a fossil fuel economy. I believe they've already started a few large ones out west.

 

[Fitz]

Dams

Not to mention many proposed dams in Canada to feed our needs.

 

[Lou Hale]

I'm not sure they can bury a 300KV transmission line. Those high voltage overhead transmission lines are steel – uninsulated cable. Additionally, those voltages put off a significant EMF. I wonder if the EMF would be too strong (for living things) at ground level.

<drift>
The original engineered plan for supplying 15KV power to MW Obs was to install conduit on the side of the cog trestle. There was to be separate conduit for the power and fiber optic cable. This was the most cost effective way to get power and communication to the summit. Unfortunately, the engineer couldn't demonstrate code compliance so that scenario was scrapped.

Eventually they engineered direct burial 15KV cable for power and buried conduit to install the fiber optic cable. This method was vastly more expensive (monitarily & enviromentally) but was code compliant and will probably last a lot longer than exposed conduit.
</drift>

I know they are developing direct submersion cable for the use in the distribution of offshore wind power. Not sure what voltages those will be rated for.

Hold on tight, you're going to see more and more above ground transmission projects in the future as we move away from a fossil fuel economy. I believe they've already started a few large ones out west.

more drift on your drift. I didn't think engineers needed to demonstrate code compliance and if so I wonder what the specific issue is 15KVish is a pretty common supply voltage and should have lots of off the shelf solutions

I think they can bury 300KV cables its just unimaginably expensive. The real worry for me would be current leakage 300K volts can overcome a lot of resistance

 

[Craig]

more drift on your drift. I didn't think engineers needed to demonstrate code compliance and if so I wonder what the specific issue is 15KVish is a pretty common supply voltage and should have lots of off the shelf solutions

I can see folks eyes glassing over so I PM'd you.

 

[DougPaul]

more drift on your drift. I didn't think engineers needed to demonstrate code compliance and if so I wonder what the specific issue is 15KVish is a pretty common supply voltage and should have lots of off the shelf solutions

15KV is too low for long-distance lines. Think more like 345KV. There are also 765KV lines. (The Soviet Union once operated a 1150KV line.) The higher the voltage, the lower the losses, but the more clearance required. However, for a given amount of power, the higher voltage line requires less horizontal space than multiple lower voltage lines. (Example: one 765KV line requires a 200ft cut, but the six 345KV lines required to carry the same amount of power would require a total of 900ft of cut.)

DC lines also have some advantages over AC lines.

Ref: Wald, Matthew L., "How to Build the Supergrid", Scientific American, Nov 2010, pp 57-61. http://www.scientificamerican.com/article.cfm?id=how-to-build-the-supergrid

My eyes hadn't glazed over and I didn't get the PM, so I figured I post...

Doug

 

[MichaelJ]

There are certainly 100kV and higher lines under the streets of Boston and surrounding towns. However, and I don't know what is the controlling factor, some of them are oil-filled.

But as Doug points out ... this is a DC transmission line. It doesn't need three-phase lines spread out across the arms of a tower, there's no phase. It needs only one line, but hopefully they'll use two, as there are detrimental environmental effects to having voltage return through the ground. Voltages can be up to the 600kV range.

One thing I didn't know until researching this was that a steady wind across a DC transmission line can produce a corona effect, losing voltage and producing ozone. There are ways to mitigate this, of course, and the number one is burying. In fact, buring an unshielded return cable is much cheaper than a second shielded cable, but will mitigate the effects of having a ground return.

 

[Davehiker]

It's interesting to me that much of the "Central Section First Alternative," and the "Preferred Route" parallels an existing high-voltage right of way from near Bath as far south as Salisbury, crossing it in Bath, and again in Groton. I seem to remember that that existing line comes from Quebec to the Comerford converter station in Monroe, and continues at least as far as Manchester. I wonder if it's more cost effective to build a new right of way than to share one with another company.

I'm a layman and have little knowledge of power transmission, but it seems to me that a significant advantage of small solar and wind power projects is that the power is produced closer to where it's used, reducing the need for long-range transmission lines. As long as we continue to use more electricity, the infrastructure must grow to continue reliable service.

 

[DougPaul]

But as Doug points out ... this is a DC transmission line. It doesn't need three-phase lines spread out across the arms of a tower, there's no phase. It needs only one line, but hopefully they'll use two, as there are detrimental environmental effects to having voltage return through the ground. Voltages can be up to the 600kV range.

Actually, one can use two DC phases: plus and minus...

With two wires, one can be run positive (+1/2) and the other negative (-1/2) (or +1 and -1 to double the effective voltage) which has advantages over running a hot wire (+1) and a ground (-0).

That said, I don't know what industry practice is with regard to single vs double wire DC transmission systems.


There is a bunch of general info at http://en.wikipedia.org/wiki/Electric_power_transmission.

Doug

 

[DougPaul]

I'm a layman and have little knowledge of power transmission, but it seems to me that a significant advantage of small solar and wind power projects is that the power is produced closer to where it's used, reducing the need for long-range transmission lines. As long as we continue to use more electricity, the infrastructure must grow to continue reliable service.

One of the problems with solar and wind is that the best locations for the power generators tend to be far from the consumers. Thus a high-capacity power grid will be required if they are ever to produce large fractions of the power used by consumers.

And integrating wind generators into the power grid can actually increase the overall CO2 output because of changes that must be made elsewhere to handle the unpredictable variable output of wind generators. I read recently that while Denmark has about 20% of its power generated by wind there is no overall reduction of CO2 production.

Doug

 

[el-bagr]

I'm interested to see this discussion here -- dealing with transmission lines from Canada, and their policy implications, is part of what I do for work. Canadian generators (like Hydro-Quebec and Nalcor) have large amounts of hydropower and other generation north of the border, far in excess of local demands. In fact, last Friday I met with Canadian developers in Boston, many of whom were very eager and open about wanting to supply power to New England and the US.

Personally, I think Lou Hale is right when he suggests that the costs of burying any significant length of a 1200 MW HVDC line are staggering. Northern Pass proposes to construct a single circuit ~345kV HVDC above-ground transmission line. Generally, towers for that size of line are mounted about 90 feet to 135 feet tall. It proposes to acquire a 150' wide right of way from the border in northern Coös County to the Lost Nation substation in Northumberland 45 miles away. From the Lost Nation substation south to a converter station in Franklin, Northern Pass's proposed new line would be located largely within an existing transmission ROW. They can deviate from that initial route, but generally in so doing incur higher costs or environmental consequences.

Davehiker, you're right that distributed generation can play a role in meeting electric demand requirements while minimizing transmission costs. There are federal and state policies that promote distributed generation for just those reasons. On the other hand, the magnitude of the Canadian renewable generation is so large that developers argue that it is less costly and less environmentally harmful, even though it requires expensive transmission lines.

Keeping this thread germane: I suspect many of us have crossed part of the transmission system in question, hiking along the AT from Mount Wolf north to the Kinsmans. According to Guy Waterman, Nathan Kinsman settled in the Easton Valley in 1782 and cut a cart path over the Kinsman Ridge through a notch where the present power line and the Reel Brook Trail cross. Perhaps it's only natural that this route would be attractive to a transmission developer today.

Fascinating to see this discussion here. I write a daily blog about energy policy issues, like Canadian power imports. If you're interested, you can read it here:
http://www.energypolicyupdate.blogspot.com/

 

[RoySwkr]

Keeping this thread germane: I suspect many of us have crossed part of the transmission system in question, hiking along the AT from Mount Wolf north to the Kinsmans. According to Guy Waterman, Nathan Kinsman settled in the Easton Valley in 1782 and cut a cart path over the Kinsman Ridge through a notch where the present power line and the Reel Brook Trail cross.

Apparently this was originally called Kinsman Notch, with the notch to S being Lost River Notch

The present powerline location was also proposed as a route for I-93 with many AMC officials preferring it to Franconia Notch, but as we know it didn't happen

 

[Waumbek]

So how does the argument in this link relate to the discussion at hand about the prohibitive expense of burying the Northern Pass HVDC line?

http://www.renewableenergyworld.com...und-hvdc-power-costs-no-more-than-ugly-towers

 

[MichaelJ]

The phrase in this article about "rapidly becoming cheaper" is actually a link to another article about HVDC Light, which refers to small and medium size transmissions of 5-150 megawatt, with accordingly small/light hardware.

The Northern Pass talks about bringing 1,200 megawatts into NH. That's going to take much more serious hardware, cabling, installation, etc.

 

[peakbagger]

May I point out that NH is named the "Granite state". It is very rare in northern NH to have any major excavation project that doesnt run into solid ledge. The PNGTS natural gas line went way over budget several years ago when they had to blast a major portion of the line through the state. I would expect burying a new transmission line would run into a similiar issue.

High voltage transmission lines are out of my league, but I do know that air cooling medium voltage lines can be smaller for an equivalent amperage than wires in conduits. Repair of above ground lines is a lot easier, they can be spliced readilly in place. Splicing an underground line is a far greater challenge, it can and is done but requires specialized equipment plus access the site of the problem whihc can be a challenge if it is under a river or in a wetland.

 

[Remix]

Just a comment, but here in Connecticut people and certain entities have been so opposed to building new transmission lines that the Federal Government imposed a "congestion charge" on many Connecticut resident's electricity bill.

Ironically the money goes to pay owners of older, inefficient, and dirtier plants to keep them running because power cannot be brought into the region from elsewhere.

 

[Spiny Mouse]

Close to Home

Interesting. My home is directly adjacent to the existing power line corridor easement where they wish to put the new HVDC line.

I walk my dog, ride my mountain bike, and cross country ski on the trails under the existing power lines. The easement is only 300 feet from where I'm sitting right now.

Having the corridor so close is actually a nice aspect of where I live. The trails I use wouldn't exist without the corridor. The shrub type vegetation attracts deer and birds who otherwise wouldn't be around here. This isn't wilderness, but it is the big outdoors.

Recently, Unitil made a major upgrade to the transmission lines along the corridor, replacing one of the original 3-phase systems that was many decades old (1957?) with a new system of taller towers which actually have a much smaller footprint on the ground.

Before they did this work, they sent us a letter explaining their project to us. They had to cut trees along the corridor, but within the existing easement to get the new line in, prior to removing the old line. I'm heating my home right now (as I type!) with one of the oak trees they cut down then. I haven't received any notice from them of this proposed new line. I imagine they will need to notify all abutters at some point.

Also, there is already an HVDC line from Hydro-Quebec running through NH down to Boston. I've spotted it north of Littleton, crossing Interstate 89 near Concord, and at the intersection of Routes 101 and 114 in Bedford. It's easy to identify because it has only two main conductors instead of the usual three.

I've had the opportunity to tour both the Manic 2 and Manic 5 hydro dams in Quebec. These are truly impressive structures of the mega-engineering sort. Do a google map search for Manicouagan Reservoir in Quebec. It'll knock your socks off. Check out http://en.wikipedia.org/wiki/Manicouagan_Reservoir to see where some of the power you're using now comes from.

 

[peakbagger]

The hydro quebec DC line actually runs through Northern Vt before swinging over to the NH side of the river. I think it crosses over somewhere around Moore Dam near Littleton. I speculate that the routing of the line through northern NH rather than colocating on the VT section is to avoid the state of VT environmental and development regs that delay any major project in the state. The PNGTS gas line did a similiar rerouting around 10 years ago where they skipped the Portland Pipeline right of way through VT before rejoining it in Gorham NH.

"Clean Canadian Hydro" isnt, it is very similiar to the Dickey Lincoln proposed project in nortnwestern maine of many years ago but on a much larger scale. There were many protests by the local native tribes when the first dams went in. Eventually they were bought off and that model is being used for the new dams.