T&D World Magazine
transmission

Why Not a National Grid?

We talked about this for years – why isn't it going anywhere? Or is it? Join the discussion as the experts respond.

One of our readers sent in a question to the Grill the Grid Masters contest. The question sparked such an interesting and informative discussion among our experts that we decided to publish the comments as a separate article. 

You, the reader, are invited to jump in. Tell us what you think in the comment section below.

Question:

For years we've talked about a national grid network so that power and load would be shared from coast to coast. Now with wind and solar in the equation it seems even more important. For example, solar from the west could be shared with the east coast after the after the sun has gone down in, say, New York. Also, the intermittency of wind (and solar) would be reduced if it could be averaged over the national geography. So, are we close to achieving a national grid. If not, why not?

Responses from the experts:

Concentrate Different Forms of Generation

For technical, political and economic reasons the concept of a national grid has never progressed beyond the discussion phase. The region west of the Rockies and the state of Texas for the most part remain separated from the rest of the country. Some degree of greater connectivity between all regions of the U.S. is probably desirable but not to move solar power from coast to coast. A better notion is to concentrate different forms of generation in areas best suited for specific applications. For example, siting solar installations in the southwest and wind generators in the northern regions of the midsection of the country and relying on an expanded grid to distribute the different types of power over manageable distances to maintain overall reliability. Obviously for the foreseeable future this would also involve the movement of significant amounts of fossil fuel generated power to make it all work practically and economically.
Matthew C. Cordaro, Ph.D.
Director
Center for Management Analysis
Long Island University

No

My short answer is no. And the reason is political and lack of national willingness to build a national (read: governmental) grid.
Mietek Glinkowski
Director of Technology, Power Products
ABB

Europe's Experience

Speaking as a European with limited knowledge of the United States, efforts have been made to integrate the activities of different TSOs in Europe resulting in ENTSO-E's Ten year Development Plan, which covers most of Europe and identifies points where cross-border connections need reinforcement. In principle, the United States could do something similar. In Europe political involvement is mostly limited to recognizing the need and providing the money. I see no reason why a similar approach could not be applied elsewhere.

Some "quick fixes" that could raise transmission capacity (for the transportation of RES power) include: dynamic line rating and carbon-cored conductors. In the case of dynamic line rating, this is proving quite useful in Europe since peak power demand tends to occur in cold weather (I understand that the reverse is true in the USA). Elia the Belgian TSO has been running its 380kV lines at 200% capacity due to this technique. Some quite nice equipment is available to facilitate line characterisation. Coupled to the carbon-cored conductors this gives a very substantial increase in line rating (200%).

Moving into the big money area, HVDC could provide a solution and could be implemented on existing towers (thus addressing the wayleave problem). This would solve the North-South problem in Germany and perhaps the east-west problem in the USA. However, the issue will be how to implement on networks running at capacity.

At the distribution level we considered converting a 33kV line to HVDC (with earth return path). Could be a bit entertaining if the earths are not set up correctly.

There we are, the view from Europe.
Mike Parr
Systems Engineer UK DNO:
Merseyside & North Wales Electricity Board O&M and New Build
Senior Authorised Engineer to 33KV

HVDC, Public Enthusiasm

One difference: due to the longer distances involved, many transmission links at least in the Western U.S. tend to be (angle-) stability constrained, rather than up against their thermal limits. Stability may or may not become an increasing concern as rotating synchronous machines are being replaced with inverter-based generation. So, HVDC is definitely the technical option on the table, especially if existing rights-of-way can be used. It's still a hard financial pitch, what with natural gas prices as low as they are -- and, as was noted earlier, public enthusiasm for new transmission is not that great (regardless of whether it's proposed by a private company or government agency).
Dr. Alexandra “Sascha” von Meier
Co-Director for Electric Grid Research
California Institute for Energy and Environment

 

Alternatives to Large Transmission

Given this nation’s recent history with storms and terrorism, perhaps we should consider alternatives to building large, highly vulnerable transmission lines, which as Sascha correctly notes are tough to site and finance. It seems to me that distributed generation, with a bias toward renewables and possibly coupled with strategically placed – yet limited – transmission lines, might be the best alternative … for reasons of reliability, security, and reality. As for financing, I would suggest that large utilities step up to make this happen: They have access to financial markets, they have relationships with residential, commercial, and industrial customers, they have the mechanisms in place to bill those very customers for services, and they have crews (or could develop and train crews) to install and maintain that equipment. Given current law, this may have to be accomplished through subsidiaries, but it is a huge opportunity, and an opportunity is a terrible thing to waste.
Lee Harrison
Contributing Writer
Transmission & Distribution World

A Mix, and New Technologies

The story seems to be progressing nicely. There is probably a compelling argument to consider a “national” grid that would allow nation-wide grid access to connect all resources and markets, but as has been mentioned a number of times in different contexts, the idea of a national interconnected AC system using conventional technology probably doesn’t make sense for a number of technical, economic and political reasons. Solutions have been proposed in this string of conversations ranging from long-distance HVDC to microgrids, while increasing the capacity and functionality of our current AC system with DC conversion of AC lines, dynamic ratings (thermal, and I’d suggest angular as well), and high-temperature, low-sag conductors. Each taken alone offers some solutions but poses other challenges, e.g., HVDC crosses many political jurisdictions, microgrids - unless interconnected over a large geography - face local resource adequacy difficulties, etc. Some mix of these might be optimal. I’d suggest considering adding another technology and configuration to the mix: AC/DC/AC interties throughout the interconnection that would create a capability of dynamic islanding and a “prophylactic” for market participation with reduced risk of spreading cascading outages. The total mix of options would allow for very flexible grid configurations as one national grid, smaller regional grids and local microgrids that would allow every electric customer access to any power market while offering maximum supply security. Is it affordable. Beats me. I guess it depends on the costs, including the diseconomies, of the alternatives. One alternative, to which Sascha alluded, is natural gas, and that I think introduces a wildcard into the mix, both as an energy resource and an energy carrier.
Dr. Merwin Brown
Co-Director, Electric Grid Research
California Institute for Energy and Environment

 

Congestion

There is already a "national grid" of sorts in the US.  States within the eastern and western systems have been interconnected since the late 60's to early 70's.  Asynchronous ties link the western and eastern interconnects. The first of seven such ties was installed in 1976.  There are also two asynchronous ties linking ERCOT with the eastern interconnect.  A similar situation exists in Canada with its eastern and western interconnects and asynchronous Quebec.  Furthermore, British Columbia, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick and, most recently, Alberta are interconnected with the US.  This transmission network was developed by multiple parties, e.g. investor owned utilities, federal power marketing agencies, public power agencies, G&T cooperatives, large municipals and provincial governments. More recently private developers have been successful in building new transmission.  The Pacific AC and DC Interties are prime examples of joint private and public transmission development.  They nicely complement one another. 

The uneven distribution of load and resources, particularly renewables, and siting issues have led to transmission congestion.  Strategically placed transmission overlays can serve to alleviate this congestion.  AC offers the advantage of easier access along the transmission path. DC offers the advantages of lower cost for long distance bulk power transmission, and controllability for bypassing congestion.  The problem is who plans, builds, owns and pays for the transmission overlay necessary to provide access to remote renewable energy. 

It is interesting to note that countries with very high penetrations of non-hydro, renewable energy also have the highest electricity rates, e.g. Denmark and Germany. 

http://spectrum.ieee.org/energywise/energy/policy/germany-could-face-electricity-customer-revolt   
Mike Bahrman
HVDC Business Development
ABB

Interties Should be Beefed Up

Point well taken. There are three major interconnections in the US and Canada, and a small part of Mexico. As you mention, asynchronous interties are what link those three main interconnections. However only a small amount of power flows through those interties. Once at a conference, a speaker was promoting a single interconnection for North America, stating that those “weak” asynchronous interties should go away. My reaction was that the opposite should happen; they and more should be beefed up and utilized to create a national grid.
Dr. Merwin Brown
Co-Director, Electric Grid Research
California Institute for Energy and Environment

Just to Add Fuel to the Fire

At the last CIGRE Plenary Session in Paris on Aug. 26, 2012, there was a keynote presentation from Zhenya Liu, President of State Grid Corporation of China who outlined, down to the technical specifics , details, economics, routes, etc. the connection between Europe and China. For me it was an unprecedented and even a bit controversial vision but... it has been presented to over 4000 participants of that conference.

For those of you who are CIGRE members it is definitely a presentation worth reviewing. I would not go into the controversial part of it but the vision could be realized at least from the technology point of view. The distance of thousands of miles is now achievable either with UHV AC or DC and "follow the sun" concept might not be such a SciFi dream as it might seem.
Mietek Glinkowski
Director of Technology, Power Products
ABB

­DC Should Be Increased

I agree with Merwin.  The number and capacity of DC interconnections should be increased.  If done in a rational manner (admittedly a big assumption in today’s political environment), it could (as previously mentioned) improve reliability and limit the potential for cascading blackouts.  Additionally, it could link energy producers with energy buyers across regions. 

As Paul pointed out in his Aug. 21 article on solar, there are times when California experiences relatively high solar production at times of low system load.  This condition currently occurs in ERCOT with wind during the spring.  At these times the combination of high supply and low demand combine to depress energy prices.  Occasionally, bid prices in ERCOT have gone negative as producers needed to get wind energy into the market in order to claim their Production Tax Credits.  Strong DC links between regions could provide market access for surplus energy of all varieties including wind and solar. 

Here’s one to think about.  Would it be possible to implement these DC interties as Merchant Transmission Providers?  Under normal conditions such providers would respond to market conditions and be paid for the transmission services as part of interregional energy transactions.  During system emergencies, system operators could require these entities to transport energy at pre-arranged prices for reliability purposes
John H. Baker Jr.
Inception Energy Strategies, LLC

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