http://www.civilbeat.com/posts/2012/04/27/15675-uncovering-the-truth-about-the-undersea-cable/
Uncovering the Truth About the Undersea Cable
by Henry Curtis
I challenge anyone to find a factual error in the following story.
Hawaiian Electric Company (HECO) asserts that the State of Hawai'i is unique in that Hawai'i has six separate transmission grids, located on the islands of Hawai'i, Maui, Moloka'i, Lana'i, O'ahu, and Kaua'i. These grids are not interconnected. If something goes wrong with one grid, that grid cannot import power from somewhere else, unlike the U.S. continent.
From 1971-2002, HECO proposed building a 138-kV high voltage transmission line between the Kamoku Substation near Iolani School and the Pukele Substation in the mauka section of Palolo.
HECO asserts that there were two distinct proposals (1971-84 & 1994-2002).
In 1971 HECO filed a request for the Kamoku-Pukele transmission line to the Hawaii Public Utilities Commission (PUC). Thousands protested. In 1984 HECO informed the Federal Energy Regulatory Commission (FERC) that they had closed their financial line item for their proposed transmission line.
In 1994 HECO filed a Conservation District Use Application (CDUA) with the Department of Land and Natural Resources (DLNR). Three groups intervened: Malama O Manoa, The Outdoor Circle, and Life of the Land. In 2002 the Board of Land and Natural Resources (BLNR) rejected the HECO application.
HECO asserted during the Kamoku-Pukele (Wa'ahila Ridge) transmission line fights, that if one transmission line is down for maintenance and a second one fails, a third line is needed. This need for three transmission lines permeates justifications that HECO, MECO and HELCO have asserted for the past few decades for proposed transmission lines.
HECO also maintains what it calls spinning reserve. This is similar to a racecar revving at a red light. In case the 200 MW Campbell Industrial Park AES Coal Plant suddenly crashes, there must be sufficient HECO generators available, that can immediately increased their output to make up for this sudden loss.
HECO terms their reliability standard the N-1-1 standard. The grid must be able to survive when one transmission or generation unit is out for maintenance, and a second one fails.
On October 15, 2006, HECO had a line load of 837 MW and spinning reserves of 275 MW when an earthquake struck off Hawai'i Island. HECO immediately lost 230 MW of on-line load (Kahe 5 and 6) followed by another 68 MW of on-line load (Kahe 3 and Honolulu 8). This resulted in a total on-line loss of 298 MW. In addition, these four generators had 95 MW of spinning reserve which was also lost. HECO experienced a cascading failure, resulting in the wiping out the O'ahu grid.
HECO, MECO and HELCO transmission grids are based on alternating current (AC). To minimize line loss HECO proposes that the interisland cable use direct current (DC). Thus the proposed Maui County wind farms would be connected to an AC/DC conversion station, then a DC high voltage undersea transmission line, then another AC/DC conversion station, and then to the HECO AC grid.
HECO has teamed up with the (1) Hawai'i Natural Energy Institute (HNEI) which is part of the University of Hawai'i, Manoa; (2) National Renewable Energy Labs (NREL), which are affiliates of the U.S. Department of Energy; and (3) the Hawai'i Department of Business, Economic Development and Tourism (DBEDT).
HECO, HNEI, NREL and DBEDT believe that new wind data collection points can be established and new computer models can be developed that will give some predictability to short-term wind forecasts. This should help determine how much wind can be absorbed by the utility grid and any given time.
None of these four entities has published any document, cited any document, or referenced any document, that discusses failure rates of AC/DC conversion stations and/or dc transmission lines.
There are only a handful of undersea high voltage transmission lines within the U.S. All of these were installed in the last few years.
One undersea cable often cited by DBEDT is the Neptune Regional Transmission System (NeptuneRTS), a 65 mile, 660 MW, dc transmission line running between New Jersey and Long Island, New York. The Neptune system went on-line in 2007. It has had a reliability factor of 98 percent. That is, 2 percent of the time there is either a planned outage for maintenance or an unplanned outage (failure).
Another undersea cable often cited by DBEDT and HECO is the Trans Bay Cable, a 53 mile, 400 MW, dc transmission line running between the City of San Francisco and the City of Pittsburgh in the East Bay. Completed in 2010, the line failed in its first week.
No piece of equipment is 100 percent reliable. HECO, MECO and HELCO assert that they must be extra cautious because they have isolated grids and they can not rely on others when there is a grid failure.
Assume that a single undersea transmission line is constructed which brings 400 MW of wind energy from Maui County to O'ahu.
Any one of the three pieces of equipment could fail – either AC/DC converter station or the dc line.
A 400 MW loss would knock out the O'ahu grid, resulting in a 24-36 hour blackout. To alleviate this, three separate undersea transmission lines must be built, each with their own AC/DC converter stations.
If the wholesale cost of wind is 13 cents per kilowatt-hour and the wholesale cost of each of three cables is 8 cents per kilowatt-hour, then the wholesale cost of inter-island wind/ three cable is 37 cents per kilowatt-hour. Added to this, is the cost is on-island transmission and distribution costs, metering, sales, administrative costs and overhead. So we are looking at a retail rate of about 60 cents per kilowatt.
To date, proponents have only argued for the unreliable single cable, and to expend ratepayer money studying the issue. Those arguing for Senate Bill (SB) 2785 state it only creates a regulatory structure for undersea high voltage transmission lines, and does not actually endorse any proposed line. But what is also does, is to give state blessing to more ratepayer studies focusing on the unreliable single transmission cable concept. Surely lawmakers can think of better ways of helping some of us to recover from the recession.
About the author: Henry Curtis has been Executive Director of Life of the Land since 1995, and has a BA in Economics from Queens College, City University of New York. He is a community organizer, videographer, director, producer, peer reviewer, moot court judge, community facilitator, and provides expert testimony on ocean power, biofuels, energy, and externalities at the Public Utilities Commission, where he has represented Life of the Land in over twenty regulatory proceedings. He is committed to Hawaii’s energy self-reliance and well-being, and is motivated by the values of aloha aina, malama aina, and his love for Hawaii nei.
Posted by Henry Curtis on 04/27/2012
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