Polar Consult ACEP HVDC P2, Final Report.pdf - Alaska Center for

662 Pages·2012·26.58 MB·English

HVDC TRANSMISSION SYSTEM
FOR RURAL ALASKA APPLICATIONS

Phase II ‐ Prototyping and Testing

May 2012
FINAL REPORT, Version 1.1

project administrator
Alaska Center for Energy and Power
University of Alaska, Fairbanks
814 Alumni Dr.
P.O. Box 755910
Fairbanks, Alaska 99775
Phone: (907) 474‐5402
funding agency
The Denali Commission
510 L St., Suite 410
Anchorage, Alaska 99501
Phone: (907) 271‐1414
prepared by
polarconsult alaska, inc.
1503 West 33rd Avenue, Suite 310
Anchorage, Alaska 99503
Phone: (907) 258‐2420
FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

About the Cover Image:
The cover image is of a demonstration installation in Fairbanks of a guyed fiberglass pole similar in size, height,
and construction to the poles considered in this study for overhead transmission in rural Alaska applications. The
pole is a 12‐inch‐diameter, 60‐foot‐tall fiberglass structure supported by three micro‐thermopiles. The pole’s
four guys are anchored by two micro‐thermopiles and two screw anchors set in silt‐rich permafrost.

MAY 2012
FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

EXECUTIVE SUMMARY
Program Objectives
This report presents the achievements and findings of Phase II of the “High‐Voltage Direct Current
(HVDC) Transmission Systems for Rural Alaska” research and development (R&D) program. The
goal of this program is to improve the economic viability of Alaska’s rural communities by
providing more affordable electricity transmission alternatives. Phase II work was funded by the
Denali Commission and completed by Polarconsult Alaska, Inc. (Polarconsult) under contract to the
Alaska Center for Energy and Power (ACEP).
The effect of excessive energy costs continues to degrade the quality of life in Alaska’s rural
communities and places these indigenous populations at severe risk. Nearly 80% of rural
communities are dependent on diesel fuel for their primary energy needs. Some of the poorest
households spent 47% of their income on energy in 2008, more than five times the amount in
Anchorage (CWN, 2012).
HVDC interties will support more cost‐effective development of local energy resources, such as
wind, hydro, biomass, geothermal, hydrokinetic, gas, and coal. Reducing the cost of low‐power (1
megawatt [MW] and less) interties by using HVDC systems can enable increased interconnection of
rural communities to Alaska’s abundant energy resources.
HVDC interties will also benefit rural communities with reduced energy costs by building
economics of scale in rural power grids and allowing utilities to consolidate bulk fuel facilities and
diesel electric power plants into more efficient and lower‐cost configurations.
As a result of ongoing advances in power electronics, small‐scale HVDC interties are now feasible.
This report has identified low‐power overhead and submarine HVDC transmission systems as an
economically superior alternative to conventional alternating current (AC) interties. Additional cost
reductions can be realized by integrating HVDC systems with future expansion of broadband fiber‐
optic telecommunication networks. This synergistic opportunity between the telecommunications
and electric industries is one of several reasons HVDC interties can help surmount the economic
barriers facing Alaska’s rural communities.
Comparative analysis of HVDC transmission systems with conventional AC systems indicates
significant technical and economic advantages of HVDC systems. In many rural Alaska applications,
the use of HVDC systems will significantly lower intertie costs.
Phase II Objectives and Findings
Phase II of this R&D program follows the Phase I – Preliminary Design and Feasibility Analysis Final
Report (Polarconsult, 2009). Phase I tasks included assessing converter technical feasibility and
evaluating the economics of a low‐power HVDC system sized for rural Alaska applications. Based on
the favorable results of the Phase I project, the following Phase II objectives were established:
● Confirmation of the technical feasibility of the HVDC/AC power converter technology by
designing, building, and testing a full‐scale prototype of a 1‐MW bidirectional power
converter and key transmission system elements.
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FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

● Confirmation of the economic feasibility of the low‐power HVDC system in rural Alaska
applications by determining the commercial cost of the converter, the converter’s efficiency,
and the estimated overall costs of an HVDC system.
● Development of cost estimates for HVDC transmission systems and comparison with
conventional AC systems to quantify the benefits and savings of HVDC systems.
Phase II has demonstrated that the converter technology is technically viable and the transmission
system is economically feasible. Key Phase II findings are:
● Low‐power HVDC converter technology is expected to be commercially available at $250
per kilowatt per converter.
● Estimates of construction costs for a conceptual 25‐mile overhead HVDC intertie indicate
capital cost savings of approximately 30% compared with a conventional overhead AC
intertie. Estimated life‐cycle costs range from 79% to 107% of the life‐cycle cost of an AC
intertie.
● Longer overhead HVDC interties can expect capital cost savings of up to 40%.
● Phase II analysis also indicates that significant savings are possible for submarine cable and
underground cable applications using HVDC systems. Estimated capital cost savings on a
25‐mile low‐power HVDC submarine cable intertie are over 50% compared to AC
alternatives.
Based on Phase II findings, the benefits of low‐power HVDC systems for Alaska are substantial, and
continued development of this system is recommended.
Opportunities and Barriers
Based on analysis and study conducted during this Phase II project, Polarconsult has concluded that
this HVDC technology presents the following opportunities for Alaska’s utility industry and rural
communities:
● Less expensive rural electric interties, leading to lower‐cost energy and increased energy
independence for rural communities.
● Interconnection to currently stranded local energy resources.
● Interconnection cost savings by combining rural electric and telecommunications interties.
The successful commercialization and adoption of low‐power HVDC technology in Alaska requires
overcoming the following barriers:
● Completion of the commercial development and demonstration of the converter technology.
Continued development of the prototype converters, culminating in independent testing of
the converters and deployment on an Alaska utility system, is needed to prove that the
converters are a commercially viable technology.
● Acceptance and use of low‐power HVDC technology by Alaska’s utility industry. Continued
involvement of in‐state and international stakeholders with the ongoing development of
this technology is considered necessary to surmounting this barrier.
● Development and demonstration of standards and control protocols for low‐power
multiterminal direct‐current (MTDC) transmission networks, which are needed to build
cost‐effective regional HVDC power networks in rural Alaska.
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FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

Recommendations
Based on the conclusions and findings of this project, the following actions are recommended:
Phase III program activities:
● Continued development of the power converter technology to commercialize the existing
prototype converter design. Solicitation of additional HVDC converter manufacturers is
warranted to encourage diversity of suppliers and competition;
● Independent testing of the converters to validate efficiency and performance, followed by
deployment on an Alaskan utility system to validate functionality and reliability in a
commercial setting;
● Further development of MTDC transmission systems interconnection and control
technologies; and
● Continued involvement of in‐state stakeholders in the development of this technology.
Stakeholder actions:
● Incorporate low‐power HVDC technology into Alaska’s regional and statewide energy plans
and policies;
● Continue coordination with the State of Alaska to allow a project‐specific waiver of the
National Electrical Safety Code (NESC) to allow the use of single‐wire earth return (SWER)
circuits;
● Encourage planned rural power and telecommunications interties to incorporate HVDC
technology in their economic and technical analysis, as well as their environmental and
permitting review processes;
● Engage the telecommunications industry to raise awareness of the synergies possible
between low‐power HVDC transmission and fiber networks in rural Alaska; and
● Collaborate with international stakeholders to identify synergies and lessons learned from
parallel technology development efforts. Coordinate on development of applicable
policies/standards and identification of markets to help expedite the commercialization and
reduce the costs of low‐power HVDC systems.

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FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

TABLE OF CONTENTS
EXECUTIVE SUMMARY ........................................................................................................................................................... I 
1.0  INTRODUCTION ........................................................................................................................................................ 1 
1.1  REPORT ORGANIZATION ...................................................................................................................................................2 
1.2  ACKNOWLEDGEMENTS ......................................................................................................................................................3 
1.3  DISCLAIMER .........................................................................................................................................................................4 
1.4  COPYRIGHT NOTICE ...........................................................................................................................................................4 
2.0  BACKGROUND ............................................................................................................................................................ 5 
2.1  PROGRAM OVERVIEW ........................................................................................................................................................6 
2.2  STAKEHOLDER ADVICE ......................................................................................................................................................7 
3.0  HVDC TRANSMISSION SYSTEM DESCRIPTION ............................................................................................ 8 
3.1  HVDC BACKGROUND ........................................................................................................................................................8 
3.2  HVDC SYSTEM CONFIGURATIONS ................................................................................................................................ 10 
3.3  COMPARISON OF AC TO HVDC TRANSMISSION ......................................................................................................... 16 
3.4  OVERHEAD INTERTIE ALTERNATIVES ......................................................................................................................... 17 
3.5  SUBMARINE CABLE INTERTIE ALTERNATIVES ........................................................................................................... 19 
4.0  HVDC CONVERTER STATIONS ......................................................................................................................... 20 
4.1  OVERVIEW ........................................................................................................................................................................ 20 
4.2  CONVERTER DEVELOPMENT OVERVIEW ..................................................................................................................... 20 
4.3  ADDITIONAL EQUIPMENT .............................................................................................................................................. 28 
5.0  DESIGN CONCEPTS FOR OVERHEAD INTERTIES .................................................................................... 29 
5.1  OVERHEAD DESIGN APPROACH .................................................................................................................................... 29 
5.2  GEOTECHNICAL CONDITIONS ........................................................................................................................................ 30 
5.3  ENVIRONMENTAL LOADS ............................................................................................................................................... 30 
5.4  CONSTRUCTION, RUS STANDARD PRACTICE .............................................................................................................. 30 
5.5  CONSTRUCTION, ALASKA‐SPECIFIC CONCEPT ............................................................................................................ 31 
5.6  TESTING OF OVERHEAD DESIGN CONCEPTS ............................................................................................................... 32 
6.0  SYSTEM ECONOMICS ........................................................................................................................................... 37 
6.1  COST COMPARISON OF AC AND HVDC OVERHEAD INTERTIES .............................................................................. 37 
6.2  CASE STUDIES .................................................................................................................................................................. 41 
7.0  CONCLUSIONS AND RECOMMENDATIONS ................................................................................................ 49 
7.1  CONCLUSIONS ................................................................................................................................................................... 49 
7.2  OPPORTUNITIES AND BARRIERS ................................................................................................................................... 49 
7.3  RECOMMENDATIONS ....................................................................................................................................................... 50 

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FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

LIST OF TABLES
Table 6‐1 Estimated Life‐Cycle Costs for 25‐mile Overhead AC and HVDC Interties ...................... 39
Table 6‐2 Summary of Case Studies ...................................................................................................................... 42
Table 6‐3 Estimated Cost for a Greens Creek – Hoonah HVDC Intertie ................................................. 44
Table 6‐4 Estimated Benefit‐Cost Ratio of Greens Creek – Hoonah HVDC Intertie .......................... 45
Table 6‐5 Estimated Installed Cost for a 5‐MW Pilgrim Hot Springs – Nome Intertie .................... 48

LIST OF FIGURES
Figure 3‐1  Typical Large HVDC Station .................................................................................................................... 9 
Figure 3‐2  Three Types of Interties Used in HVDC Systems ........................................................................ 11 
Figure 3‐3  Monopolar HVDC Intertie Using SWER ........................................................................................... 12 
Figure 3‐4  Monopolar HVDC Intertie with Return Conductor (SWER‐capable for Backup) .......... 13 
Figure 3‐5  Bipolar HVDC Intertie (SWER‐capable for Backup) .................................................................. 14 
Figure 4‐1  Low Voltage Alternating Current (LVAC) Enclosure: Mechanical Layout ........................ 22 
Figure 4‐2  HVDC Transformer Tank: Mechanical Layout ............................................................................. 23 
Figure 4‐3  Central Resonant Link Test Setup ..................................................................................................... 25 
Figure 4‐4  Hi–Pot Test Setup for HVDC Transformer ..................................................................................... 25 
Figure 4‐5  Dry System Inverter Mode Test Schematic and Setup.............................................................. 26 
Figure 4‐6  System #1 HV Tank and LV Enclosure ............................................................................................ 27 
Figure 4‐7  System #1 Showing HV Measurement Probes ............................................................................. 27 
Figure 5‐1  Installing Micro‐Thermopile for Guy Anchor ............................................................................... 33 
Figure 5‐2  Assembling the Prototype GFRP Pole Splice ................................................................................ 34 
Figure 5‐3  Prototype GFRP Pole Foundation During Installation .............................................................. 35 
Figure 5‐4  Prototype Pole at the Fairbanks Test Site ...................................................................................... 36 
Figure 6‐1  Comparative Installed Cost: Overhead 1‐MW HVDC and AC Interties .............................. 38 
Figure 6‐2  Comparative Life‐Cycle Cost: Overhead 1‐MW HVDC and AC Interties ............................ 40 
Figure 6‐3  Location Map for Potential HVDC Project Sites ........................................................................... 41 
Figure 6‐4  Greens Creek – Hoonah Intertie Route ........................................................................................... 43 
Figure 6‐5  Prospective Transmission Route from Pilgrim Hot Springs to Nome ................................ 47 
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FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

APPENDICES
APPENDIX A HVDC OVERVIEW ............................................................................................................................ A‐1
APPENDIX B ECONOMIC ANALYSIS ................................................................................................................... B‐1
APPENDIX C CONCEPTUAL DESIGN OF OVERHEAD HVDC INTERTIE LINES ................................. C‐1
APPENDIX D CONCEPTUAL DESIGN FOR SUBMARINE CABLES ............................................................ D‐1
APPENDIX E SWER CIRCUITS AND HVDC SYSTEM GROUNDING ......................................................... E‐1
APPENDIX F HVDC POWER CONVERTER DEVELOPMENT ..................................................................... F‐1
APPENDIX G HVDC SYSTEM PROTECTION, CONTROLS, AND COMMUNICATIONS ...................... G‐1
APPENDIX H CANDIDATE HVDC SYSTEM DEMONSTRATION PROJECTS .......................................... H‐1
APPENDIX I STAKEHOLDER ADVISORY GROUP INVOLVEMENT AND MEETINGS ........................I‐1
APPENDIX J BIBLIOGRAPHY .................................................................................................................................. J‐1

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FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

ACRONYMS AND TERMINOLOGY
°F degrees Fahrenheit
A, a, i amperes or amps
AC alternating current
ACEP Alaska Center for Energy and Power
ACSR aluminum conductor steel reinforced
ADNR Alaska Department of Natural Resources
AEA Alaska Energy Authority
AEL&P Alaska Electric Light and Power Company
AFI Arctic Foundations, Inc.
AKDOL Alaska Department of Labor
albedo The extent to which an object diffusely reflects light.
alternating The form of electricity commonly used in homes and businesses in which the
current current and voltage oscillate at a frequency of 60 cycles per second. (The
frequency in some nations is 50 cycles.)
Alumoweld A type of cable used in electrical systems. Each strand of the cable consists of a
steel core with a layer of aluminum extruded over it during the pulling and
drawing process. The steel core provides increased strength, and the aluminum
exterior provides better corrosion protection and increased electrical
conductivity.
amperes/ A measure of the amount of electrical current flowing through a circuit (a typical
amps household circuit is rated for 20 amperes).
AP&T Alaska Power and Telephone Company
APA Alaska Power Association
ASCE American Society of Civil Engineers
AVEC Alaska Village Electric Cooperative, Inc.
AVR automatic voltage reference
bandwidth A measure of the data transfer capability of a given communications method.
Units of bandwidth can vary but are generally bits per second.
BEC Bethel Electric Utility
bipolar A type of direct current circuit that uses two wires to transmit energy. Bipolar
circuits operate one wire (“pole”) at a positive potential and the second pole at a
negative potential relative to ground (e.g., +/‐ 600,000 volts). These circuits
normally also have an earth return pathway or a dedicated ground conductor that
is used to compensate for any imbalance on the two poles and serves as a
temporary return pathway if the negative or positive pole is out of service for any
reason.
BSNC Bering Straits Native Corporation
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FINAL REPORT, VERSION 1.1 POLARCONSULT ALASKA, INC.
HVDC TRANSMISSION SYSTEM FOR RURAL ALASKAN APPLICATIONS
PHASE II – PROTOTYPING AND TESTING

Btu British thermal unit
CEA Chugach Electric Association, Inc.
CIGRE Internationale des Grands Reseaux Electriques
circuit A circuit provides an electrical pathway from a point of energy supply (e.g., a
generator or battery) to a point of energy use (e.g., motor, lighting, etc.), and then
back to the point of supply. Without a complete pathway from supply to use and
back, the circuit will not function. The pathway can take many forms. Most
commonly, it is made of metallic (copper or aluminum) wires, but it can also use
water, the earth, or other materials. These other materials are most often used on
the return pathway back to the point of supply, where the voltage differential
relative to the surrounding environment is low.
conductor A typically metallic wire or cable that is designed and fabricated to conduct
electricity between two locations.
converter An electrical device that converts electricity from AC to DC and/or from DC to AC.
“Converter” is a more general term for a rectifier or inverter.
CVEA Copper Valley Electric Association, Inc.
DC direct current
direct current Direct current is the form of electricity commonly used in battery‐powered
devices such as cars, flashlights, etc. The current does not appreciably vary with
time.
distribution Refers to lower‐voltage electrical systems. Definitions vary, but systems operating
class at or below nominal 35 kilovolts (kV) are generally classified as distribution‐class.
Most rural Alaska interties function as transmission systems, but operate at
distribution‐class voltages, typically 14.4 kV.
earth return A means of completing an electrical circuit by using the earth as a return path
instead of a second wire. In many nations, this approach is frequently used in
rural areas where (1) the cost to install a second wire for the return path is
prohibitively high and (2) the lack of buried utilities ensures that technical issues
with ground return are minimized.
EHS extra‐high‐strength
EPR ethylene propylene rubber
fiber optics A communications method that consists of sending pulses of light down glass
fibers.
FO fiber optics
ft‐lb foot‐pound
gal gallon(s)
GEC Gustavus Electric Company
GFRP glass‐fiber‐reinforced polymer
GPS Global Positioning System
GVEA Golden Valley Electric Association, Inc.
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