Transmission System and Renewable Generation Integration Issues

What do you think is the largest problem we are going to have with our existing transmission lines in the next ten years?

The biggest problem is that electricity for all customers may not be available on demand. To ensure that that problem does not occur means that the transmission system must be upgraded in accordance with industry and government expectations and timeline.

Factors contributing to transmission system inadequacy are:

(1) Age of transmission system in some areas of the United States, e.g. northeast and midwest.

(2) Population shifts (Reference 1)

(3) Reduced investment in the transmission system for almost 25 years (Reference 2)

(4) Technology change

(5) Housing Boom (Reference 3)

(6) Connecting new generation

Since energy storage has been, and will continue to be, a lower priority for the short-term future, generation must be matched with demand. Cost pressures also play a role. If local generator sources available are more costly to run (e.g. gas or diesel generators) or cannot supply load fast enough, the regional system dispatcher will seek supply elsewhere. The transmission system links users with generators. As an example, a utility in Minnesota may purchase power from a utility in Tennessee if the cost of the power supplied plus transmission charges are less than what the cost would be for the local utility to startup its own unit. Locally, similar transfers occur between Oregon and Washington and California through the high voltage AC and DC lines near The Dalles. Such routing through common lines can result in high current flows or low voltages in the system. As a result, a localized event, e.g. a power plant trip off-line, a substation transformer failure, transmission system relay failures, could result in a significant regional grid failure as the northeast blackout which occurred most recently in 2003 (Reference 4).

Electrical transmission systems must be in synch with the population shifts. Since 1900, the populations of the southern and western states have had higher increases than the northeast and midwest (Reference 2). Since 1970, electricity demand has increased at a 2.4% average annual rate. This is due to 3 factors (1) population increase, (2) technological change (e.g. central air conditioning, computer use, call centers), (3) increasing size of new homes (1500 square feet to 2350 square feet between 1970 and 2004). (Reference 3). During recessions, one can expect reduced demand.

The transmission system issue arises from several causes depending on which part of the US you are concerned with.

  1. The eastern United States has a number of older systems that cannot adquately handle the increased current flow, directional changes, or demand.
  2. The western United States is still building transmission systems to handle the population shifts. Between 2008 and 2018, the western interconnection is expected to add 14000 miles of transmission or 47% of the total US transmission lines to be added.
  3. All areas of the US have experienced the need to add transmission as additional generation has been added and will continue to have to be added. (Reference 5)

The transmission system has been experiencing bottlenecks where demand cannot be met or can only be met at a higher cost, e.g. more expensive local generation. (Reference 6)

To facilitate transmission siting in the national interest, Congress passed the Energy Policy Act of 2005. Two National Interest Electric Transmission Corridors have been designed. (References 7,8,9).

There is no doubt that more investment must be made in transmission systems, however, that pales with the investment that must be made in generation. Transmission system cost is only about 6% of the final retail electric cost. (Reference 10). This cost is borne first by the transmission company, local utilities, or regional operator. In the US, slightly more than 70% of the transmission systems are owned by investor owned utilities, the remainder by the government. (Reference 11). The other 94% covers the investment in generating, distribution, and control facilities.

As a country, US electrical demand per capita ranks in the top 10 nations. (Reference 12) However, it is important to realize that residential demand is dwarfed by commercial and industrial demand. While individually we may be able to reduce demand, the major challenge is for companies to reduce demand and/or improve energy efficiency.

A review of the Department of Energy, North American Electricity Reliability Corporation, Federal Energy Regulatory Commission, and National Renewable Energy Laboratory and US Senate documents indicate many of the issues and problems are being identified and worked through (References 13-30).

I agree with many of the comments made, particularly those regarding house size, smart grid and transmission construction challenges.

The following are suggested as ways to address current and future challenges to the transmission system:

  1. Upgrade the transmission system to deal with component aging, out-of-date design, and new generation.
  2. Ensure adequate redundancy in the design to reduce the current and prior problems with bottlenecks.
  3. Provide encouragement for investor-owned companies or require participation by the federal and state governments in investment in transmission systems in cases where private investment is not possible.
  4. Minimize the legal challenges to the national interest and other transmission corridors.
  5. Provide incentives to encourage landowners and federal/state government agencies (e.g. Forest Service) to allow transmission system easements. The social upheaval that surrounded installation of the 500 KVDC western Minnesota CPA-UPA line in the late 1970s should be avoided (Reference 19).
  6. Provide incentives to encourage societal changes to reduce electrical demand. One way of doing this is to develop methods of on-site energy generation that would reduce demand on the transmission system. Possibly the mortgage crisis will encourage builders and potential homeowners to invest in small energy-efficient houses that they can afford.


1. Demographic Trends in the 20th Century, Census 2000 Special Reports, Frank Hobbs and Nicole Stoops, November 2002.

2. Our National Transmission System Today and Tomorrow, Lawrence Berkeley Laboratory, Figure 1.4

3. Electricity: The Next Energy Jolt?, Kevin L. Kliesen, The Regional Economist, October 2006, Federal Reserve Bank of Saint Louis.

4. Final Report on the August 14, 2003 Blackout in the United States and Canada: Causes and Recommendations, U.S.-Canada Power System Outage Task Force, April 2004,

5. 2009 Long-Term Reliability Assessment 2009-2018, October 2009, North American Electric Reliability Corporation. 2009 _LTRA.pdf

6. U.S. Department of Energy Transmission Bottleneck Project Report, March 19, 2003, Jim Dyer, Electric Power Group, Consortium For Electric Reliability Technology Solutions (CERTS).

7. National Electric Transmission Corridor Report and the Ordered National Corridor Designations, DOE Office of Electricity Delivery & Energy Reliability.

8. Mid-Atlantic Area National Corridor Map

9. Southwest Area National Corridor Map

10. Reliability of the U.S. Electricity System: Recent Trends and Current Issues, page 7

11. The Changing Structure of the Electric Power Industry 2000 : An Update, Chapter 3,

12. List of countries by electricity consumption, Wikipedia

13. Annual Energy Outlook 2010 with Projections to 2035, US Energy Information Administration

14. Executive Summary of the North American Electric Reliability Corporation (NERC) special report, Accommodating High Levels of Variable Generation, April 2009.

15. Department of Energy Wind Energy Resource Potential and Wind Energy Projects

16. Cape Wind

17. Bing search cape wind opposition

18. Electricity Transmission: A Primer, National Council on Electric Policy, June 2004

19. Wikipedia CU Project Controversy

20. Eastern Wind Integration and Transmission Study: Executive Summary and Project Overview , January 2010

21. Eastern Wind Integration and Transmission Study , January 2010

22. Western Wind and Solar Integration Study: Executive Summary , May 2010

23. Western Wind and Solar Integration Study , May 2010

24. Federal Energy Regulatory Commission, Transmission Line Siting,

25. Moving Beyond Paralysis: How States and Regions Are Creating Innovative Transmission Projects May 2009 May 2010 , NREL/SR-550-46691, October 2009

26. Generation Interconnection Policies and Wind Power: A Discussion of Issues, Problems, and Potential Solutions, NREL/SR-550-44508, January 2009

27. FERC Order 2003, Standardization of Generator Interconnection Agreements and Procedures, July 2003

28. Transmission Cost Allocation Methodologies for Regional Transmission Organizations , NREL/SR-550-48738, July 2010, page 4

29. Historical Tables; Budget of the U. S. Government , Table 1.1, Summary Of Receipts, Outlays, And Surpluses Or Deficits (): 17892015

30. Fiscal Year 2011 Budget of the United States Government

As a follow-on to my earlier discussion, I believe that the transmission system will not be upgraded as expected. Traditionally major construction projects fall behind schedule. When you consider all of the hurdles encountered in buying property or getting easements, getting the necessary local, state, and federal (if necessary) approvals, completing the design, and then doing the construction.

The actual construction involves siting and installing the necessary substations, installing the needed tower bases (excavating, pouring, and curing) and towers, then hanging the wires and insulators. For the step-up and step-down transformers there is usually a long lead time. Transformer construction depends on meeting close tolerances, excellent control of the materials used in the transformer, good quality control in the construction followed by satisfactory acceptance testing. It may take 1-2 years between the time a transformer is ordered and it is delivered on-site.

The page shows a new substation in Klickitat County specifically built to add renewable energy from the wind turbines (also shown).

Renewables Home - Virtual Nuclear Tourist - Tuesday March 29, 2011