HomeMy WebLinkAboutSE Alaska HVDC Sys Report Update 2-2011Southeast Alaska HVDC System Report 6-Draft 3-10-11.docx
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CITY AND BOROUGH OF SITKA, ALASKA
SITKA-KAKE-PETERSBURG
INTERTIE STUDY UPDATE
February 2011
DR. GEORGE KARADY – Professor and consultant
F. MIKE CARSON - Northstar Power Engineering
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SITKA-KAKE-PETERSBURG HVDC INTERTIE STUDY
George G. Karady and F. Mike Carson
2011
Executive Summary
The objective of this study is to assess the feasibility to interconnect Sitka-Kake-Petersburg
when the Takatz Lake Hydro is built. The proposed line would constitute an important
section of the Southeast Alaska Intertie Plan. The system capacity would be rated at 50 MW.
This will permit energy transfer between Sitka, Kake, and Petersburg. The intertie would also
provide back-up power during faults in local generation. A similar study was prepared 10
years ago by the same authors. After reviewing several feasible system configurations, this
study concluded that a multi-terminal voltage source converter based High Voltage Direct
Current (HVDC) system in a bi-polar configuration was the most economical system for the
intertie. The major advantages of the multi-terminal HVDC system are the active, reactive
power control, and black start capability. The final conclusion was that HVDC Light system
made by Asea-Brown-Boveri (ABB) would be the best solution.
In the last 10 years the voltage source based multi-terminal HVDC become a matured
product, more than eleven (11) systems are in operation. In addition to ABB,
manufacturers like Siemens and Areva also offer a similar system. However, the market
has changed in the last 10 years and the cost of IGBT converters and DC cable
increased significantly. ABB proposed 50MW, 80 kV converters at an estimated cost of
$35M.
Another market change is that the manufacturers are not interested in building small
HVDC Light or HVDC Plus systems. Indian and Chinese markets as well as the
European offshore wind farms demand large, several hundred megawatt ratings for the
voltage source based HVDC systems. The manufacturers are working on large IGBT
based HVDC systems which can compete with the classical thyristor based HVDC and
suitable to form DC networks.
ABB suggested building a traditional 138kV, 50MW AC intertie with submarine cable
compensated by reactance. System operation analysis proved that the submarine cable
capacitive current can be compensated with two reactances. This system is close to 36
million dollars cheaper than lowest cost HVDC system. The intertie will use the 138kV
and 69kV transmission lines, which are already in operation in Alaska. The new
component is the submarine cable and its compensation with two inductances. The one
line diagram of the recommended 138kV and 69 kV systems is shown in figure below.
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Table of Contents
Executive Summary .................................................................................................................. 2
List of Figures ........................................................................................................................... 5
List of Tables ............................................................................................................................ 6
1 Nomenclature .................................................................................................................... 7
2 Introduction ....................................................................................................................... 7
3 Objectives ......................................................................................................................... 9
4 Description of the Proposed Line ..................................................................................... 9
5 Present State of Voltage Source Converter Based HVDC Systems ............................... 12
5.1 HVDC with Voltage Source Converter .................................................................. 13
5.2 HVDC Substations .................................................................................................. 17
5.3 HVDC Cables ......................................................................................................... 20
1 Manufacturers Data ......................................................................................................... 26
2 Conceptual design and cost estimate .............................................................................. 29
2.1 Hybrid system ......................................................................................................... 31
2.2 Hybrid system-Alternative 1 ................................................................................... 31
2.3 Hybrid system Alternative 2 ................................................................................... 35
2.3.1 Transmission Line and Cable Cost Estimate ...................................................... 36
2.3.2 Hybrid System Alternative 1 & 2 Cost Estimate ................................................ 36
2.4 Multi-Terminal DC System .................................................................................... 39
2.4.1 Multi-Terminal DC System Alternative 1 .......................................................... 39
2.4.2 Multi-Terminal DC System Alternative 2 .......................................................... 42
2.4.3 Budgetary Cost Estimate for Multi-Terminal HVDC Light Systems ................. 42
2.5 AC transmission System with compensated submarine cable ................................ 43
2.5.1 Analysis of the Three Phase AC Intertie Operation ............................................ 44
2.5.2 Budgetary Cost Estimate Three Phase AC System............................................. 46
2.6 Summary of the Comparison of Different Systems ................................................ 46
3 Conclusions ..................................................................................................................... 47
4 References ....................................................................................................................... 47
5 Biosketches ..................................................................................................................... 48
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List of Figures
Figure 1 Proposed Intertie between Sitka-Kake-Petersburg ..................................................... 9
Figure 2 Direct Buried DC Cable in Sweden .......................................................................... 11
Figure 3 HVDC Solid state converter development. (Copy Panel 02-1 Overview of HVDC
Transmission, ABB WEB site). ...................................................................................... 12
Figure 4 HVDC system with voltage source converter .......................................................... 14
Figure 5 StakPak module of IGBT’s ...................................................................................... 15
Figure 6 Arrangement of Heat sinks and IGBT modules ....................................................... 15
Figure 7 IGBT valves used for light HVDC ........................................................................... 16
Figure 8 Multi-level converter for the HVDC Plus system. ................................................... 16
Figure 9 HVDC plus valve. .................................................................................................... 17
Figure 10 Conceptual design of a HVDC light substation ..................................................... 18
Figure 11 IGBT valves mounted in metal enclosures ............................................................. 18
Figure 12 Light HVDC station ............................................................................................... 19
Figure 13 Pair of extruded polymer HVDC cables. ................................................................ 19
Figure 14 DC submarine cable ............................................................................................... 20
Figure 15 Giulio Verne Cable Laying Ship ............................................................................ 21
Figure 16 138kV Cross-linked polyethylene Cable ................................................................ 21
Figure 17 Circuit diagram of a PWM converter ..................................................................... 23
Figure 18 PWM voltage waveform ......................................................................................... 23
Figure 19 Generation of PWM voltage waveform ................................................................. 24
Figure 20 Example for a planned multi-terminal DC system ................................................. 25
Figure 21 Sitka’s Electric Energy Requirements and Resource ............................................. 30
Figure 22 Hybrid system conceptual connection diagram ...................................................... 31
Figure 23 69 kV transmission tower used in Sitka area .......................................................... 32
Figure 24 138 kV transmission tower used in Petersburg area ............................................... 33
Figure 25 Multi-Terminal DC Transmission System. ............................................................ 39
Figure 26 The S1 composite insulator .................................................................................... 40
Figure 27 Three phase AC transmission system ..................................................................... 43
Figure 28 Equivalent circuit for the Three phase AC transmission system ............................ 44
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List of Tables
Table 1 Light HVDC Systems ................................................................................................ 13
Table 2 HVDC light submarine cables (Extract from ABB Brochure “HVDC Light Cables”)
......................................................................................................................................... 34
Table 3 HVDC light Converters (Extract from ABB Brochure “HVDC Light Cables”) ....... 35
Table 4 HVDC Light Submarine Cables (Extract from ABB Brochure “HVDC Light
Cables”)........................................................................................................................... 35
Table 5 Variation of Consumer Price Index between 1999-2010 ........................................... 37
Table 6 ABB Provided Cost Data ........................................................................................... 38
Table 7Hybrid systems with HVDC light, Alternative 1:69 kV and 138 kV transmission lines
and 80 kV DC submarine cable ...................................................................................... 38
Table 8 Hybrid system with HVDC light, alternative 2:138 kV transmission lines and 80 kV
DC submarine cable, 80 kV ............................................................................................ 39
Table 9 Technical Specification of MacLaen Composite Insulators. (Copy from MacLaen
Catalouge) ....................................................................................................................... 40
Table 10 IEC 515 Recommended Creapage Distances for Polluted Insulators. (Copy from
IEC 515) .......................................................................................................................... 41
Table 11 Cost Estimate for the Multi-Terminal HVDC Light System Alternative 1 ............. 42
Table 12 Cost Estimate for the Multi-Terminal HVDC Light System Alternative 2 ............. 43
Table 13 Data for Operation Analysis .................................................................................... 44
Table 14 Cost Estimate for the AC Transmission System ...................................................... 46
Table 15 Cost Comparison of Different Systems ................................................................... 46
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SITKA-KAKE-PETERSBURG HVDC INTERTIE STUDY
1 Nomenclature
• HVDC High Voltage DC energy transportation system
• HVDC Light Asea_Brown Bovery (ABB) developed DC energy transportation
system using voltage source converters
• HVDC Plus Siemens developed DC energy transportation system using voltage
source converters
• IGBT Insulated Gate Bipolar Junction Transistor, suitable for high
frequency switching.
• Thyristor High power switching device, which can turn on a circuit, but it
turns off when the current reverses.
• Monopolar DC A DC system which has only one current carrying conductor and
the current returns through the earth
• Bipolar DC A DC system, which has two current carrying conductors and a
neutral conductor. No ground current
• Hybrid system An energy transportation system that has AC lines and DC
submarine cable
• Multi-terminal DC A DC system, which contains more than one converter connected
in parallel to the system.
• Converter Electronic circuit that can work as a rectifier or as an inverter
2 Introduction
Southeast Alaska Transmission Intertie includes the interconnection of the Sitka and
Petersburg electric power systems, via Kake. The area requires interconnections between
islands close to each other as well as rough mountainous terrain with several meter yearly
snow fall. The load on the interconnection varies between 2MW-50MW.
Several studies investigated the design, budgetary cost and specifications of the Southeast
Alaska Transmission Intertie. The major studies investigating the transmission and
generation aspect of the Intertie are:
1. Transmission Intertie, Kake-Petersburg, A Reconnaissance Report, Alaska Power
Authority, Robert W. Retherford Associates, January 1981
2. Tyee-Kake Intertie Project, Detailed Feasibility Analysis, Volumes 1 and 2, Alaska
Power Authority, EBASCO, March 1984
3. Feasibility Study, Kake-Petersburg Intertie, State of Alaska-Department of
Community and Regional Affairs, Division of Energy, R.W. Beck, June 1996
4. Takatz Creek Project-Alaska, U.S. Department of the Interior, Alaska Power
Administration, 1960.
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5. Analysis of Electric System Requirements, City and Borough of Sitka, R. W. Beck,
April 1974
6. Electric Resource Evaluation and Strategic Plan, City and Borough of Sitka, R.W.
Beck, November 1991
7. Southeast Alaska Intertie DC Transmission System- Reconnaissance Design and Cost
Estimate, Teshmont Consultants, November 1982.
8. Southeast Alaska Transmission Intertie Study, Alaska Power Authority, Harza
Engineering, October 1987
9. Southeast Alaska Electrical Intertie System Plan, Southeast Conference, Acres
International, January 1998.
10. Sitka-Kake-Petersburg HVDC Intertie Study, Northstar Power Engineering, George
G Karady, and F. Mike Carson. January 1999
11. Southeast Alaska Intertie Study, Southeast Conference, D. Hittle and Associates,
December 2003
12. Kake-Petersburg Intertie Study, Southeast Conference, D. Hittle and Associates, July
2005
13. Kake-Petersburg Intertie Study Update, Southeast Conference, D. Hittle and
Associates, May 2009
14. Takatz Overhead Transmission Line Alternative Feasibility Review Report Summary,
Commonwealth Associates, February 10, 2011.
These studies recommended different solutions and provided budgetary cost estimates. Harza
Study [#8] and our [#10] ten years old study proposed the building of a high voltage DC
transmission system. The main reason is that the capacitive current limits the length of an AC
underwater cable in the 30-40miles. Simultaneously the DC cable technology improved in
the last 20 years and the economic building of long HVDC cables with solid dielectric
material (cross linked polyethylene) became feasible.
In our previous study [#10] we showed that building of a traditional HVDC system using
thyristor based current commutated converters are not economical for the short (less than 50
miles) distances and for low power (50MW or less). According to the literature, the
traditional HVDC system is economical above around 300miles length and 500MW power
transfer.
In the last 10 years, the technology for the voltage source converter based multi-terminal
HVDC system further developed. Originally, this system was designed for low power and
short distance energy transport. Small HVDC transmission systems have been built (ABB
and Siemens) and are operating successfully. Technology matured and more manufacturers
offer voltage source converter based multi-terminal HVDC systems. However, the cost of the
converters remained high, which upset the advantages of the HVDC system. The above
described development suggests an investigation of all feasible alternatives both AC and
voltage source converter based HVDC systems for the Sitka-Kake-Petersburg Intertie.
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3 Objectives
The objective of this study is to investigate the most feasible interconnection for the planned
Sitka-Kake-Petersburg Intertie.
The study will investigate:
1) The technical advantages of the proposed system including:
i) Emergency power in case of power plant outage
ii) Voltage support in case of overload
iii) Load flow control
iv) Blocking the development of cascading outages
v) Transient stability improvement
vi) Inter-area (small signal) oscillation damping
2) Description of the project and identification of major components
3) Economic evaluation and budgetary cost estimate
4 Description of the Proposed Line
A comprehensive description of the proposed intertie was provided in our last report [#10].
In this report the intertie description was updated and slightly modified to conform to the
City’s latest plans.
Presently, Sitka is supplied by the Blue Lake (7.0MW) and Green Lake (18.54MW) hydro
plants and some diesel generation. 69 kV transmission lines connect the power plants to the
city of Sitka.
Approximately 22 miles northeast of Sitka is Takatz Lake, where a 28MW hydro power plant
can be built. This plant would produce excess energy that could be sold to Kake and
Petersburg. However, this requires an intertie between Sitka, Kake, and Petersburg.
Figure 1 Proposed Intertie between Sitka-Kake-Petersburg
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The intertie would start from the Blue Lake 69 kV switchyard and connect the proposed
Takatz Lake Hydro to the Sitka system using an AC overhead line with segments of
underground/submarine cable. In the other direction, a submarine cable would connect the
Takatz Lake powerhouse to Kake. From Kake, an overhead line with two short submarine
cable crossings would connect to the existing 138kV Petersburg-Tyee Lake transmission line.
The investigation of the present loads and the rather moderate expected load growth by the
City of Sitka suggested a tie line capacity of 50 MW.
Figure 1 shows the proposed intertie route. It can be seen that the intertie is divided into
three main sections.
1. Blue Lake switchyard to Takatz Lake powerhouse (21.2 miles transmission line). The
terrain between the two sites is extremely rugged, with two mountain passes. One pass is
between Takatz Lake and Baranof Lake (elevation 2100 ft) and the other is between
Baranof and Medvejie Valleys (elevation 2500 ft). The new transmission line would start
at an overhead tap on the existing Green Lake 69 kV transmission line near Bear Cove
about 5.0 miles southeast of Blue Lake Switchyard. The transmission line would follow
the Medvejie Valley easterly past Medevjie Lake. At the head of the valley, a tunnel
would be bored into nearby Baranof Valley to avoid the steep rugged mountain pass.
Underground transmission cable in conduit would be used in the 2.0 mile long tunnel.
The new transmission line would continue east along the Baranof Valley to Baranof
Lake. Heavy duty H-frame structures would be used for this 6.2 mile segment. Then the
new transmission line would continue along the north side of Baranof Lake to a point
west of the community of Baranof where the line would turn north and follow along the
east side of Sadie Lake. At the upper end of Sadie Lake, the line would cross the steep
ridge and continue down to the south side of Takatz Bay where it would bifurcate.
Heavy duty H-frame structures would be used for this 5.3 mile segment. Then the line
would either continue west to the powerhouse or would continue east to a submarine
cable landfall on Chatham Strait. Heavy duty H-frames would be used because of the
terrain.
2. Takatz Lake Power House to Kake (41.1 miles submarine cable). Harza proposed a 100
kV submarine cable from Warm Springs Bay to Point White at a total distance of 35
miles (56.3 km). This submarine cable route was modified to connect to the selected
submarine cable landfall on the south side of Takatz Bay. The new submarine cable
would cross Chatham Strait and Frederick Sound near the tip of Admiralty Island. The
maximum water depth is about 350 fathoms that requires double armored cable. Harza’s
proposed landfall at Point White also was modified. The new landfall would be at the
Kake Substation site southeast of Kake (Point K in the 2009 Kake-Petersburg Intertie
Study Update Report) to avoid a transmission line through the center of town and by the
airport.
3. Kake to Petersburg (50.0 miles transmission line and 1.8 miles submarine cable). From
the cable landfall at the Kake Substation site, an overhead transmission line would
continue southeast across Kupreanof Island to Duncan Canal and Wrangell Narrows
where two submarine cable crossings would be located. Single pole structures would be
used for this line. The line would connect to the existing 69/138 kV Petersburg-Tyee
Lake overhead transmission line near Papke's Landing. The proposed route has been
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identified as the Center-South Alternative and is described in detail in the 2009 Kake-
Petersburg Intertie Update Report by Hittle and Associates.
The latest Acres International Corporation study estimated the cost of this intertie to be about
US $65-$66 million, where the first two sections (Kake-Sitka) is estimated at US
$45,489,000 in 1996 dollars and the Kake-Petersburg section at US $19,734,600 in 1996
dollars. The 2009 cost estimate for the Center-South Alternative in the Hittle Kake-
Petersburg Intertie Update Report is $37,922,200 (Table 4-3)
DC cables can be direct buried or placed in conduit. Figure 2 shows an example of direct
buried crosslink polyethylene DC cable. This example suggests the investigation of using
DC cables instead of 69 kV overhead lines if an access road is available. Deep snow would
not jeopardize the operation of underground cable. An economical DC cable solution would
require the building of a primitive access road to the Takatz Lake powerhouse. However, we
understand that an access road would not be in the project plan unless the Alaska Department
of Transportation participates in the project.
Figure 2 Direct Buried DC Cable in Sweden
Our previous study suggested voltage source converter based DC system for the intertie
because the 41 mile long DC submarine cable, between the Takatz Lake Powerhouse and
Kake, would not cause a large capacitive current. The capacitive charging current limits the
length of an AC submarine cable. However, the capacitive current of the 138 kV submarine
cables can be compensated by inductances. Because of the high cost of DC converters, ABB
suggested the compensated 138 kV submarine cable as an alternative.
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The advantage of the DC link is that it eliminates the possible stability problems that could
surface in this relatively low voltage system with long lines. From a commercial point of
view, another advantage is that the DC permits accurate regulation of the power transfer from
Takatz Lake powerhouse to Kake and Petersburg. Sitka would be able to control the
distribution of the Takatz Lake hydro produced power.
Figure 3 HVDC Solid state converter development. (Copy Panel 02-1 Overview of
HVDC Transmission, ABB WEB site).
5 Present State of Voltage Source Converter Based HVDC Systems
Our previous study and the literature show that the traditional thyristor based HVDC system
is economical for transmission systems over 300 miles and 500 MW. Consequently, the
traditional DC or even with a hybrid system is not economical or feasible for the Southeast
Alaska intertie. This study will consider only the voltage source converter based HVDC and
AC systems.
The voltage source converter based HVDC system was discovered 10 years ago by ABB,
which marketed the system under the name of HVDC Light. In the mean time, Siemens
developed a similar system under the name of HVDC Plus. Also, AREVA-ALSTON recently
started building similar systems. Several new systems are in successful operation. Some of
them have close to 10 years of successful operation record.
Table 1 shows the list of existing and future HVDC projects using voltage source converters.
In addition to the DC links, the voltage source IGBT converter is used for static VAR
compensation.
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Table 1 Light HVDC Systems
Name Location Km kV MW Year Type
Terranora interconnector
(Direktlink) ABB
Australia -
Mullumbimby ABB 59 80 180 2000 IGBT
Eagle Pass, Texas B2B,
ABB USA - Eagle Pass, TX 15.9 36 2000 IGBT
Tjæreborg, ABB Denmark -
Tjæreborg/Enge 4.3 9 7 2000 IGBT
Cross Sound Cable, ABB USA - New Haven, CT 40 150 330 2002 IGBT
Murraylink, ABB Australia - Red Cliffs 177 ±150 220 2002 IGBT
HVDC Troll, ABB Norway - Kollsnes 70 60 80 2004 IGBT
Estlink, ABB Estonia - Harku 105 150 350 2006 IGBT
NordE.ON 1, ABB Germany - Diele 203 150 400 2009 IGBT
HVDC Valhall, ABB Norway - Lista 292 150 78 2009 IGBT
Trans Bay Cable, Siemens USA - East Bay -
Oakland, CA 88 200 400 2010 IGBT
Caprivi Link, ABB Namibia - Gerus 970 500 300 2010 IGBT
SydVästlänken, ABB Sweden–Hallsberg
Norway–Oslo 400 1200 2013/
2015 IGBT
The voltage source based HVDC system is designed for less power than the classical
thyristor based HVDC system. One of the major advantages is multi-terminal DC or DC
network building. Typical applications are:
• Small isolated remote load supply
• Power supply to an island or off shore oil and gas platforms
• Interconnection of asynchronous grids
• In-feed to cities by land cables
• Interconnection of small scale (low-head hydro) generation
• Connect off shore wind power generation to power grids
5.1 HVDC with Voltage Source Converter
The voltage source converter based HVDC system is a fast developing technology, which
uses insulated gate bipolar transistor (IGBT) switches and pulse width modulation (PWM).
The capacity of a voltage source converter based HVDC system is limited to 1200MW and
+/- 320kV in 2010. The semiconductor manufacturers are increasing the capacity of the
IGBT switches and as a result the capacity of the HVDC system is increasing. Presently,
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ABB and Siemens are selling IGBT’s rated 6500V, 600A for HVDC systems. The IGBT has
voltage controlled capacitive gate and it is shunted by a parallel connected diode in reverse
direction.
The first voltage source converter based HVDC was introduced by ABB in 1997. Presently
more than 10 systems are in successful operation and several new systems are under
construction. The technical parameters of the voltage converter based HVDC system indicate
that this technology produces a nearly ideal transmission component that has the potential to
change the conventional methods of electric power transmission and distribution. The market
survey shows that ABB is offering the HVDC Light system, Siemens offers the HVDC Plus
system and ALSTON-AREVA is preparing a demonstration site with voltage source
converters.
The basic module of the voltage source converter is the three phase bridge built with
Integrated Gate Bipolar Transistors, shunted by diodes in the reverse direction.
Figure 4 shows basic circuit diagram of a transmission system with voltage source
converters.
D1
IGBT1
IGBT2
D2
CDC
IGBT5IGBT3
IGBT4IGBT6
LAC
Vdc
VAC
C
B
A
CDC
D1
IGBT1
IGBT2
D2
CDC
IGBT5IGBT3
IGBT4IGBT6
LAC
VDC
VAC
C
B
A
CDC
Figure 4 HVDC system with voltage source converter
The systems supplying the converters do not need high short circuit capacity or at the
receiving end do not need to have generation. The voltage source converter can supply an
island without generation. It has black start capacity. Typically a standard transformer and a
series converter reactor (inductance) connect the converter to the network. Because of the
PWM system only small AC filter is needed.
At the DC side, two capacitors connected in series serves as a filter. The midpoint of the
capacitors is grounded. The converter is not grounded if it is a floating system.
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The converters can operate automatically without communication between the stations. The
system can regulate both the amplitude and phase angle of the AC voltage. This means the
independent regulation of the active and reactive power. The direction of power transfer
depends on the voltage. The current flows from the converter operating at a higher voltage
than the other. The reversal of the power flow requires the reversal of current direction and
not the reversal on the voltage. The system is suitable for multi-terminal operation.
Each valve consists of several hundred IGBTs connected in series. The valve is divided into
series connected modules called StakPak by ABB. Figure 5 shows the StakPak module.
Several of these modules are connected in series to form the valve.
Figure 5 StakPak module of IGBT’s
(Copy from ABB Website [1])
The IGBTs are cooled by de-ionized water. The even voltage distribution is assured by a
parallel connected voltage divider. Figure 6 shows the general arrangement of heat sinks,
IGBT modules and gate drives.
Figure 6 Arrangement of Heat sinks and IGBT modules
(Copy from ABB Website [1])
The voltage across each IGBT is rectified and provides power for the gate drive of the IGBT.
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An optical link from the ground controls the gate drives.
Figure 7 shows a section of an IGBT valve used for HVDC light systems.
Figure 7 IGBT valves used for light HVDC
(Copy from ABB Website [1])
Siemens introduced the HVDC Plus system and built the Trans Bay Cable projects in
California.
One major contribution of Siemens is the development of a new type of multi-level
converter. Figure 8 shows the basic circuit, which contains two IGBT’s and a capacitor.
Several of these units are connected in series to form the valve as shown in Figure 9.
Figure 8 Multi-level converter for the HVDC Plus system.
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Figure 9 HVDC plus valve.
Copy from Siemens Website
The VSC technology allows straightforward AC side connections. The HVDC Plus system is
supplied by standard transformers equipped with cooling fans. The HVDC Plus system is
protected by one circuit breaker per converter station, which is connected between the power
transformer and the AC network. The station can be safely isolated from both the AC
network and DC circuit with disconnect switches. The insulated AC and DC bus can be
automatically grounded with grounding switches for safety reasons. Standard surge arresters
protect the system against lightning and switching type over-voltages. On the AC side, the
voltage and current is measured by standard voltage and current transformers. The DC
voltage is measured by resistive voltage dividers and the DC current is measured with shunt
resistances.
Due to its modular construction, the HVDC Plus converter is flexible in its configuration,
which permits the use of standard components.
5.2 HVDC Substations
The HVDC substations with voltage source converters are built indoors except the
transformers. The station is built with modular equipment, in which the components are
installed in enclosures in the factory.
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Figure 10 Conceptual design of a HVDC light substation
(Copy from ABB Website [1])
Figure 10 shows the general arrangement of a voltage source converter based substation. In
this figure, three AC cables feed the substation through filters and three large series
connected phase reactors (inductance). The IGBT valves are installed in the factory in metal
clad enclosures. The rather large cooling system is adjacent to the valves. The DC side with
the filter capacitors is at the back of the substation.
Figure 11 IGBT valves mounted in metal enclosures
(Copy from ABB Website [1])
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Figure 11 shows two light green boxes containing the IGBT valve assemblies. These boxes
are assembled in the factory and transported to the site. The factory assembly is particularly
advantageous for Alaska where the construction is difficult in the winter time.
Figure 12 shows the photograph of another ABB HVDC Light substation, where the valves
are placed in a building. This substation is supplied by four transformers (one spare) and
through filters placed between the transformers and the valve hall.
Figure 12 Light HVDC station
(Copy from ABB Website [1])
In the foreground of the buildings is the cooling equipment. The fans are visible in the
picture.
Figure 13 Pair of extruded polymer HVDC cables.
(Copy from ABB Website [1])
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5.3 HVDC Cables
The voltage source based HVDC system can supply transmission lines or cables. The
advancement of cable technology promotes the use of land cables, which can be competitive
with the overhead lines in difficult terrains where a road is present.
The HVDC Light systems use extruded polymer cables for land cable. Usually, HVDC light
is an ungrounded bipolar system with a positive and a negative cable. As an overhead line, it
also needs two conductors (positive and a negative). Figure 13 shows typical polymer cable
pair designed for the HVDC Light application.
The cable has aluminum conductors surrounded by a black semi-conducting layer, which
reduces the electrical field on the conductor surface. The white extruded polymer is the main
insulation of the cable. The polymer insulation is surrounded by black semi-conducting layer
and a grounded woven copper shield conductor. The next white layer prevents water
penetration. The outer jacket of the cable is PVC.
Figure 14 shows the construction of a typical submarine cable. The coaxial single conductor
cable is XLPE insulated. The construction of this cable is more rugged than the cables used
on land. This cable has two layers of shield conductors, lead sheet and steel wire armor.
Figure 14 DC submarine cable
Submarine cable installation requires a cable laying ship. Pirelli operates the Giulio Verne
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cable ship, which is capable of laying cables in all weather conditions. Figure 15 shows this
ship that is equipped with a 7000-ton rotating turntable.
Figure 15 Giulio Verne Cable Laying Ship
Copy from Siemens Website
ABB suggested the use of a compensated 138kV submarine cable connection between Takatz
Lake and Kake. The proposed cable is shown in Figure 16.
Figure 16 138kV Cross-linked polyethylene Cable
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According to Prysmian(Pirelli) and Caldwell Marine, the installation of the proposed 138 kV
AC three conductor submarine cable is feasible but there are three extraordinary design
considerations that significantly increase the material and labor costs. The minimum
recommended conductor size for 138 kV AC cables is 750 kCM per the Association of
Edison Illuminating Companies (AEIC) standards and 600 kCM per the Insulated Cable
Engineers Association (ICEA) standards due to the electric fields. Therefore, the 185 square
mm or about 350 kCM copper conductor recommended by ABB would not meet these
standards. Since double armor is recommended for the depths up to 2100 ft. (350 fathoms) in
Chatham Strait, a three conductor 750 kCM copper 138 kV AC double armored submarine
cable would be significantly more expensive than the ABB estimate. This 138 kV AC
submarine cable also will have considerable more weight due to the larger conductors and
extra armor. When installed at 2100 depth, Caldwell Marine estimated the maximum cable
tension would be approximately 64,000 lbs. This high tension exceeds the strength of the
cable and equipment capacity. Prysmian(Pirelli) recommended a special double flat strap
cable armor that is shown in Figure 16. This special armor reduces the cable weight from 65
lbs/ft to about 57 lbs/ft. The cable weight and approximately 8” cable diameter results in a
logistics problem and Prysmian(Pirelli) indicated that the installation would have to be
performed in two separate campaigns. Only half of the cable could be laid at one time and
the cable ship or barge would have to return to port to load the remaining submarine cable.
As a result, the mobilization and demobilization cost would approximately double along with
the cost of an underwater cable splice. The closest port with the facilities to handle the
submarine cable is Seattle or in Prysmian’s case, the Guilio Verne would have to return to
Naples, Italy for the second load.
The proposed 80 kV DC submarine cables do not have similar extraordinary design
considerations that increase the material and labor costs. The required copper conductor size
for the two 80 kV DC submarine cables due to ampacity is 600 kCM so the minimum
conductor size is not an issue. The weight of 600 kCM copper conductor is about 80 percent
of 750 kCM copper conductor so the 80 kV DC single conductor submarine cable weight and
tension will be less than the 138 kV AC three conductor submarine cable and probably not an
issue. However, two passes of the cable ship or barge are required to lay the two 80 kV DC
single conductor submarine cables. According to Caldwell Marine, the estimated installation
cost to lay the two 80 kV DC submarine cables will be about $8M more than the 138 kV AC
three conductor submarine cable.
5.4 PWM technology
The modern manufacturing industry requires AC motor drives that are accurately regulated.
These drives should operate close to unity power factor and not generate significant current
harmonics in the AC supply. These requirements led to the development of the PWM (pulse
width modulation) technique. Figure 17 shows the concept of PWM and Figure 18 presents
the generated voltage waveform.
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D1
IGBT1
IGBT2
D2
CDC
IGBT5IGBT3
IGBT4IGBT6
LAC
VDC
VAC
C
B
A
Figure 17 Circuit diagram of a PWM converter
The converter in Figure 17 can operate as a rectifier or as an inverter. It is built with six
semiconductor switches, which are shunted by diodes. The semiconductor switch can be a
transistor, IGBT or a MOSFET. The six switches form a six-pulse bridge. A capacitor shunts
the DC side and three inductors are connected in series with each phase on the AC side. The
switches are turned on in sequence, e.g. 1-2, 3-4, 5-6, etc. The turn on of switch 1 connects
the positive DC terminals to phase A and the turn on of switch 2 connects the negative DC
terminals to phase B. The switches are turned on for a short period of time, which generates a
pulse train at the ac terminals.
Figure 18 PWM voltage waveform
Figure 18 shows the generated pulse train. It can be seen that the width of the pulses is
modulated and hence the name PWM. The filtering of the output voltage produces a
sinusoidal waveform.
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Figure 19 Generation of PWM voltage waveform
The generation of the PWM waveform is illustrated on Figure 19. As shown in Figure 19(a),
a high frequency triangular wave is compared with a 60 Hz reference sine wave to generate
the control pulses shown in Figure 19(b). The intersection of the triangular ‘carrier’ and the
sinusoidal ‘reference’ determines the pulse width as demonstrated in Figure 19(b). If the
sinusoidal reference voltage is higher than the triangular carrier wave, the upper
semiconductor switch (1, 3 or 5) connects the phase terminal to the positive DC terminal; if it
is lower the bottom switch (2, 4 or 6) connects the phase terminal to the negative DC
terminal.
The frequency spectrum of the generated pulse train contains the base 60 Hz component and
other high frequency components. The latter are multiples of the triangular carrier frequency.
The AC inductance blocks the current harmonics at the AC side, which are further reduced
by a high-pass filter.
The DC capacitor reduces the harmonics at the DC side. The DC capacitor also controls the
turn-off over voltages, by providing a low impedance path. The output voltage can be
controlled by the pulse pattern and by the DC voltage.
This converter can supply a passive AC system. It can be used to start an AC system after a
fault. If the AC system has a voltage source, controlling the converter voltage phase angle
can independently regulate the real and reactive power transfer. The active power depends
mostly on the converter voltage phase angle and the reactive power is dependent on the
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voltage magnitude. The converter can act as a motor or generator without mass and can
provide either capacitive or inductive reactive power. The converter controls the AC current
and consequently does not contribute to the AC short circuit current.
The PWM converter is an ideal device for energy transmission. It was proposed and
developed more than a decade ago for low power applications. The lack of high power high
frequency switches initially prevented application to HVDC systems.
For start up, the AC breaker is closed at one side. The diodes in the converter produce a DC
voltage and energize the DC line. This charges the power supplies of the gate drive units,
which permits a start of the converter operation. The first converter that starts will control the
DC voltage. The second converter that starts controls the power transfer. The reactive power
is controlled independently at each station. The active power flowing in the DC network has
to be equal to the active power transmitted from the first network to the second network plus
the losses. In this system, one converter station maintains the DC voltage constant. The other
station controls the active power flow within the limits of the system. This is achieved by
controlling the phase angle between the network voltage and the sinusoidal reference control
voltage.
If an AC fault occurs at the side that receives the power, the power-controlling converter is
blocked. This interrupts the outgoing power, but not the incoming power. This results in a
fast rise of DC voltage. The dc voltage-controlling converter will reduce or even reverse the
incoming power to maintain the DC voltage level.
If the fault occurs on the AC side of the converter that controls the DC voltage, the converter
is blocked and a sudden drop in the DC voltage occurs. In this case, the remaining converter
will control the DC voltage and simultaneously control its reactive power flow. The
operation mode of this converter will be similar to the operation of a dynamic voltage
restorer.
In case of a ground fault in the AC system, the converter control will reduce the DC voltage
to limit the current flow to the pre-fault value. The voltage source converter will not increase
the short circuit current in the AC system.
Voltage source converters can be applied to HVDC system to permit multi-terminal
operation. Several converters can be connected in parallel to a DC transmission line.
Sitka
Takatz
Hydro
Kake
Petersburg
DC Submarine Cable
41.1 mi
69kV
AC
69kV
AC 138 kV
AC
DC line
21.1 mi
DC line
44.3mi
20MW
69kV
Figure 20 Example for a planned multi-terminal DC system
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As an example if the Sitka-Kake-Petersburg Intertie is built with voltage source converters,
four converters could be connected in parallel by DC transmission lines and submarine
cables. Figure 20 shows the possible arrangement.
The problem with this arrangement is that the power requirement of the various sites is
different. As an example, Kake requires power less than a MW, the Sitka and Petersburg sites
requires 50 MW and the Takatz Lake Hydro can be operate with 25-30MW converter. ABB
suggested +/- 80kV or +/- 100kV system voltage. The cost of the small MW converters is
very high.
1 Manufacturers Data
The literature survey shows that three manufactures offer voltage source based HVDC
systems in the USA. The manufacturers are: ABB, Siemens, AREVA. All of the three
manufacturers have been contacted. We presented the map of the Sitka-Kake-Petersburg
Intertie together with the load data and requested a proposal for the system configuration (AC
or DC system), voltage level and budgetary cost estimate.
Surprisingly, the manufacturers showed very little interest to supply a HVDC system rated 50
MW. We learned that ABB and Siemens are building large HVDC systems for India and
China and has no time to work on small systems.
The E mail received from ABB states that the use of HVDC Light system is feasible but
more economical to use AC transmission for the 50MW Sitka - Kake – Petersburg intertie.
The recommendation is copied below:
“ABB recommends the following solution:
(1) Extend the 138 kV system from Petersburg to Kake by constructing a 138 kV AC line.
[50 MW transfer exceeds four times surge impedance loading for a 69 kV line which would
be at about its practical line loadability limit for the 44 MW distance.]
(2) Install a 138 kV, three-core, submarine cable between Kake and cable landing site near
Takatz Lake Hydro. Reactive power compensation may be required at Kake. Cable estimate
and technical data is provided below.
(3) Build either a 69 kV or 138 kV AC line from the Takatz Lake cable landing site to Sitka
to complete the new interconnection between Sitka and Petersburg.
(4) There is no reason to install an HVDC system for this application. If one were to do so,
however, the logical choice would be to install a 50 MW, +/- 80 kV two-terminal HVDC
Light system in symmetrical monopole configuration with two 80 kV single core HVDC
Light cables between Takatz Lake Hydro and Kake, and completing the interconnection with
AC overhead transmission as described above. Each 50 MW converter station would cost
about $35 MUS at today’s exchange rate. The system would most likely be too weak to
support conventional HVDC under all operating conditions. The HVDC cable crossing
would cost roughly about 70% that for the AC cable crossing.
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(5) The only reason to consider multi-terminal HVDC for this application is if overhead
lines are not permitted and cable must be used the entire way. Even then there would be
some issues. It would not be possible/practical to serve Kake, a load of only 2-5 MW, from a
+/- 80 kV converter. The current would be too small.
(6) Even if overhead lines were prohibited, it is probably feasible to build the entire
interconnection with AC cable, provided static and dynamic reactive power compensation
were installed at each terminal, i.e. Sitka, Takatz Lake Hydro, Kake and Petersburg. The
exact values of the reactive power compensation equipment would need to be determined by
system study.
(7) Although land cable itself would be less expensive than submarine cable, installation
cost would be much higher. Depending on the terrain, land cable installation cost could easily
run about equal to that of the cable itself. In this application, installed cost of the cable
would probably be about twice that of the overhead line as a general approximation. A
detailed estimate for the line would have to be compared with a detailed estimate for the
cable by contractor with knowledge and experience in this area.
(8) Another possible application for an HVDC alternative would be to run the 50 MW +/-
80 kV HVDC submarine cable circuit all the way through the water between Takatz Lake
Hydro and Petersburg thereby avoiding a new line between Petersburg and Kake. This may
be a competitive alternative. In this case Kake would have to served by local diesel
generation or a small AC cable from Takatz Lake Hydro.
Budget estimate for the AC cable connection only:
This budget estimate includes manufacturing and delivery of 70km 3x185mm2 138kV AC
Cable with an integrated 48 SM optical fiber cable, six terminations and one off-shore splice.
(no installation)
Item Description Quantity Unit price Total price
1 138kV Submarine Cable 70 km 425 USD/m 29 750 000 USD
2 38kV Outdoor Terminations 6 ea. 7 250 USD 43 500 USD
3 138kV Submarine cable Splice 1 ea. 40 000 USD 40 000 USD
4 Mob/demob and Transportation 1 L.S. 4 000 000 USD 4 000 000 USD
Total price: $33,833,500 US (Import duties and taxes for Alaska excluded)
Based on:
Cu = 8140 USD/ton
Pb = 2320 USD/ton
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6.64 SEK/USD exchange rate
The voltage drop will be around 2.6% for the total length of the circuit.
Cable design enclosed (DRAFT)
It is hereby understood that neither the indicative technical and pricing data, its associated
commercial terms nor any past or future action, course of conduct or failure to act by either
party regarding the project will give rise to or serve as a basis for any obligation or other
liability on the part of the parties or any of their affiliates. Neither party shall be obliged to
enter into any further agreement with the other party. Any commitment, agreement or
binding obligation with respect to the project would only arise and would be subject to,
among other things, the negotiation, the due execution and delivery by the parties of the
definitive agreement regarding the project. ("Definitive Agreement").
The recommended HVDC Light voltage, as indicated below is +/- 80 kV, with symmetrical
monopole configuration.
The cost of the +/-80 kV HVDC Light submarine cable circuit, also as indicated below,
would be about 70% that of the AC cable submarine cable circuit. Note you can prorate for
distance to determine the cost of going all the way to Petersburg through the water. We have
made no estimation for installation of the cable. Based on this the cost of the DC submarine
cable circuit (2 cables) would be 0.7 x $33.8 M = $23.7 M for the 70 km distance +
installation say + 20%.
We have made no estimation for the +/- 80 kV HVDC Light land cable, but in general it
would cost, with joints and terminations, significantly less than the submarine cables due to
use of Al conductor instead of Cu, no lead jacket, no armoring, etc. The installation cost
would be dependent on local conditions and would require input from contractor but you
could assume that installation costs with civil works would cost as much as the cable itself.
Therefore for budgetary estimating purposes, you could assume 70% the cost of the DC
submarine cable and double it to account for land installation. 0.7 x $23.7 = $16.6 M, or
$237 k/ ckt-km for cable and joints + say $200 k /ckt-km for trenching and installation =
$437 k/ckt-km but you would be better off to get estimates from local contractors for that
portion.
Hope this is adequate for you needs. Our cable folks are extremely busy with RFP's for real
committed projects and cannot really give any more detail especially in the absence of real
router data and local construction costs. “
The discussion with Siemens resulted similar results, but Siemens did not provide any
written estimate in spite of the repeated request.
The discussion with AREVA T&D resulted the following E mail:
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“ ….For the cable connection Nexans would propose 75 kV monopole configuration with
return conductor.
65 km of TKRA-L 75kV 1x300mm²
65 km of TSRA 24kV1x300mm²
Total ball park price ex-works Halden, Norway: 20 MUSD
Total weight of 2x65 km of cable as above: 1300 tonnes
Transport and installation can be estimated once we have more knowledge of project, sites,
depth etc.
Unfortunately, this leads to an asymmetrical monopole arrangement, which means the
converter transformers would be specials. I am working with Nexans to determine a more
optimized solution, based on a mid-point ground design.
As for the converters, they are IGBT-based multilevel bridges, building on our previous
experience with the multilevel GTO-based STATCOMs presently in service.
The ABB systems I believe are all 2 or 3 level configurations, although I think they are
developing a multilevel system now.
The converters for the asymmetrical solution above would probably be in the region of 30
MUSD, so I am trying to optimize this a little more with the cable design. I want to put the
voltage down and the current up, whereas they want to put the voltage up and the current
down.
FYI, here is some recent presentation material which illustrates our VSC system.
It's basically an IGBT-based multilevel converter with a maximum rating of 1250 A DC. We
can add sufficient modules in series to achieve the required DC rating. The maximum XLPE
cable rating is presently around +/-320 kV, so we can achieve up to about 800 MW at the
moment.
If you want more details please let me know. “
The two presented E-mails shows that the manufacturers are not very motivated to supply
small systems.
2 Conceptual design and cost estimate
Figure 21 shows that both load and generation will increase significantly between 2010-2030
in the Sitka area.
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Figure 21 Sitka’s Electric Energy Requirements and Resource
In spite of the expected rapid load growth, the building of Takatz Lake Hydro increases the
system capacity and produces surplus energy, which can be sold in the Petersburg area.
This justifies the 50 MW rating of the proposed intertie.
In Sitka, the existing system is rated at 69kV, while in the Petersburg area 138 kV is used.
The distance between Petersburg and Sitka is about 115 miles. A 138 kV transmission line is
marginally suitable to transport 50 MW from Petersburg to Sitka. Simultaneously, the 69 kV
line cannot transport 50 MW for such a long distance. An additional problem is the 41 mile
submarine cable between Takatz Lake Hydro and Kake. The large charging current limits the
capacity of the submarine cables. Compensation of the charging current is needed for AC
transmission or a DC link must be used.
The viable solutions are:
• Hybrid System Alternative 1: 69kV AC transmission line between Sitka and the
Takatz Lake Hydro, +/- 80kV DC submarine cable between Takatz Lake Hydro and
Kake, and 138 kV AC transmission line between Kake and Petersburg.
• Hybrid System Alternative 2: +/- 80 kV DC land cable between Sitka and the Takatz
Lake Hydro, +/- 80 kV DC submarine cable between Takatz Lake Hydro and Kake
and 138 kV AC transmission line between Kake and Petersburg.
• Multi-Terminal DC Alternative 1: +/-80 kV DC submarine cable between Takatz
Lake Hydro and Kake and +/- 80 kV DC transmission line in the rest of the intertie.
• Multi-Terminal DC Alternative 2: +/- 80kV DC submarine cable between Takatz
Lake Hydro and Kake and +/- 80kV DC transmission cable in the rest of the intertie.
• AC System with Compensated Submarine Cable. 69kV AC transmission line between
Sitka and the Takatz Lake Hydro, 138 kV compensated submarine cable between
Takatz Lake Hydro and Kake and 138 kV AC transmission line between Kake and
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Petersburg.
2.1 Hybrid system
The Alternative 1 hybrid system uses conventional AC transmission lines and HVDC
submarine cable for crossing Chatham Strait and Frederick Sound between Kake and Takatz
Lake. For Alternative 2 hybrid system, the 69 kV line is replaced by +/- 80 kV DC land
cable.
2.2 Hybrid system-Alternative 1
The use of conventional tyristor based HVDC is uneconomical for this low load and short
distance. The voltage source converter based HVDC Light or HVDC Plus has been used for
this type of submarine crossing in the past. In this hybrid system, the HVDC supplies only
the submarine cable. A bipolar, ungrounded voltage source converter based HVDC system
with +/- 80kV voltage is proposed for the submarine cable. The concept of the hybrid system
is shown in Figure 22.
At Kake, the HVDC system will be connected to the 138kV transmission line through a
transformers and circuit breakers; at Takatz Lake, the HVDC will supply the local 69 kV
lines through a transformer and circuit breaker.
The rest of the system is a conventional 69kV or 138kV AC system, with wood pole
transmission lines.
Figure 22 Hybrid system conceptual connection diagram
Sitka builds heavy duty 69 kV lines with horizontally arranged ACSR, 336.4 kCM “Linnet”
conductors. The conductor amperage is 537A, the distance between the phases is 10ft 6in, the
line resistance per phase is 0.2901 ohm/mile, the reactance is 0.764 ohm/mile, and the
capacitance is 14.68 nF/mile. Figure 23 shows the typical wood pole H-frame structure.
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Figure 23 69 kV transmission tower used in Sitka area
The distance between Blue Lake switchyard and Takatz Lake Hydro is about 22.6 miles. The
50MW load current is 523A at 69 kV. The capacity of the 336 ACSR with ampacity 537 A is
marginal for 50 MW transfer.
The voltage drop is 19.04% for the transportation of 50 MW at power factor 0.8 lagging.
This is an unacceptable high value.
Further analysis shows that a 69 kV line can transport less than 26 MW power to a distance
of 22.6 mile at power factor 0.8 lagging when the voltage drop is limited to less than less
10%.
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Figure 24 138 kV transmission tower used in Petersburg area
The line capacity can be increased by series connected capacitors. As an example, 3.5µF
capacitors connected in series with this line permit the 50 MW load at less than 10% voltage
drop and a 7 µF capacitor reduces the voltage drop to 4.82% at 50 MW load.
This calculation shows that practically all 28 MW power generated by the future Takatz Lake
Hydro can be transported by one 69 kV line to Sitka. However, if the intertie is built, most of
the Takatz lake Hydro produced power would be sold to Petersburg. The load at Sitka is less
than 25 MW; consequently, the transportation of 50 MW to Sitka is not needed even in
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emergency conditions. If the 50 MW transfer is necessary, 3-4 µF series capacitors must be
inserted in the 69 kV line at Takatz Lake or at Sitka. An alternative but more expensive
solution is the double circuit line or large conductors.
The Kake-Petersburg 50.0 mile section must be 138kV. Figure 24 shows the typical 138kV
lines used in the Petersburg area.
The 138kV line typical heights are 40ft. The line uses ACSR 336kCM conductor with
horizontal span of 350ft. A 24 strand ADSS communication cable would be placed 13 ft
under the conductor. The right of way clearance is about 60-50ft wide. The ampacity of the
ACSR 336kCM conductor is 537A and the load current at 50MW, power factor 0.8 lagging
is 261.5A. The average GMR distance is 12.51ft, the line resistance per phase is
0.2901ohm/miles, reactance is 0.758ohm/mile, and capacitance is 14.82nF/miles.
The 50 MW load produces 9.469% voltage drop at power factor 0.8 lagging. This is a
marginally acceptable value. Fortunately the HVDC can adjust the voltage and compensate
for the marginal voltage drop on the 138kV line.
Takatz Lake Hydro and Kake section of the intertie is +/- 80 kV bipolar HVDC system with
41 mile long submarine cable. The 50 MW transmission at 80 kV requires a current of 625A.
Table 6 shows submarine cables offered by ABB for a HVDC Light system.
Table 2 HVDC light submarine cables (Extract from ABB Brochure “HVDC Light Cables”)
According Table 2, the 625A load current requires 300mm2 copper submarine cables if the
voltage between the cables is 80 kV, and the cable is spaced “Close Laying”. This implies
that the line to ground voltage is only 40 kV.
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Table 3 list the converters that ABB offers for the submarine cables. The smallest converter
is the M1 unit which is rated to 102 MW. This is proof that ABB does not offer a 50 MW
HVDC light system.
The cables will be supplied by two (2) 50MW, 80kV voltage source converters with rated
current of 625A.
Considering the data in Table 3, the 50MW can be supplied by the half of the M1 converter
that is rated to 109 MW. This implies that the voltage between the cables is 80 kV and the
voltage to ground is +/-40kV.
Table 3 HVDC light Converters (Extract from ABB Brochure “HVDC Light Cables”)
2.3 Hybrid system Alternative 2
The alternative 2 hybrid system includes the addition of a DC land cable section to the
intertie, replacing the 69kV transmission line between Takatz Lake and Blue Lake
switchyard.
Table 4 HVDC Light Submarine Cables (Extract from ABB Brochure “HVDC Light Cables”)
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The terrain between these two stations is very rough, high elevation, with several meters
snow in the winter. The maintenance and repair of this line is complicated and the building
of this line would be very expensive. We recommend that the City of Sitka build a primitive
access road between Takatz Lake and the Medevejie access point, which would permit the
direct buried land cable installation or would significantly reduce the cost of overhead line
construction. Table 4 shows the land cables offered by ABB.
According to Table 4, the 625 A load current requires a land cable with 400mm2 cross
section with “Spaced laying”. This cable rating is 90MW, and ampacity is 705A in case of
“Spaced laying “. The required cable length is 22.6miles.
In this case the system needs an additional 80kV converter at Sitka. The total number of
converters needed for this alternative are three (3): Sitka, Takatz Lake and Kake.
The other components are: 50.0 miles of 138 kV transmission line between Petersburg and
Kake; 41.0 miles of 80kV DC submarine cable pair between Kake and Takatz Lake.
2.3.1 Transmission Line and Cable Cost Estimate
Single Wood Poles 138 kV AC Wood $600,000/mile
w/Access Road 69 kV AC Wood $550,000/mile
80 kV DC Bipolar $400,000/mile
Heavy duty 138 kV AC Wood $1,200,000/mile
H-Frames w/ 69 kV AC Wood $1,100,000/mile
Helicopter 80 kV DC Bipolar $800,000/mile
Construction
Submarine Cable 138 kV AC, with installation $1,494,032 /mile
80 kV DC land cable, with installation $763,684/mile
80 kV DC, with installation $1,191,120/mile
Underground Land 69 kV AC $2,000,000/mile
Cable W/Conduit 80 kV DC $1,400,000/mile
& No Road
2.3.2 Hybrid System Alternative 1 & 2 Cost Estimate
The major cost is the HVDC stations and the submarine cable. Cable selected from ABB
brochure “HVDC Light cables” is the 150mm2 submarine cable.
ABB E mail recommends:”50 MW, +/- 80 kV two-terminal HVDC Light system in
symmetrical monopole configuration with two 80 kV single core HVDC Light cables
between Takatz Lake Hydro and Kake, and completing the interconnection with AC
overhead transmission as described above. Each 50 MW converter station would cost about
$35 MUS at today’s exchange rate.”
In spite of our repeated request Siemens did not provide budgetary cost estimate for a 50
MW HVDC Light system. AREVA estimated the 50 MW converter station for $30M.
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We updated the cost estimates presented in our previous study. The mono-polar system has
been eliminated together with the parallel connected converters because both ABB and
Siemens WEB sites offer only a bipolar system.
The cost of the transmission lines was re-estimated using current data obtained from the 2009
Kake Petersburg Intertie Study Update Report. For estimation of the converter cost, the
estimates made 10 years ago were updated. The ABB provided original estimate included the
cost of interconnecting transformers in the converter price.
The expected increase of the converter price can be estimated using the variation of
Consumer Price Index. Table 5 shows the variation of the consumer price index
between1999–2010.
Table 5 Variation of Consumer Price Index between 1999-2010
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN
2010 216.687 216.741 217.631 218.009 218.178 217.965 218.011 218.312 218.439 9999 9999 9999 9999
2009 211.143 212.193 212.709 213.24 213.856 215.693 215.351 215.834 215.969 216.177 216.33 215.949 214.537
2008 211.08 211.693 213.528 214.823 216.632 218.815 219.964 219.086 218.783 216.573 212.425 210.228 215.303
2007 202.416 203.499 205.352 206.686 207.949 208.352 208.299 207.917 208.49 208.936 210.177 210.036 207.342
2006 198.3 198.7 199.8 201.5 202.5 202.9 203.5 203.9 202.9 201.8 201.5 201.8 201.6
2005 190.7 191.8 193.3 194.6 194.4 194.5 195.4 196.4 198.8 199.2 197.6 196.8 195.3
2004 185.2 186.2 187.4 188 189.1 189.7 189.4 189.5 189.9 190.9 191 190.3 188.9
2003 181.7 183.1 184.2 183.8 183.5 183.7 183.9 184.6 185.2 185 184.5 184.3 183.96
2002 177.1 177.8 178.8 179.8 179.8 179.9 180.1 180.7 181 181.3 181.3 180.9 179.88
2001 175.1 175.8 176.2 176.9 177.7 178 177.5 177.5 178.3 177.7 177.4 176.7 177.1
2000 168.8 169.8 171.2 171.3 171.5 172.4 172.8 172.8 173.7 174 174.1 174 172.2
1999 164.3 164.5 165 166.2 166.2 166.2 166.7 167.1 167.9 168.2 168.3 168.3 166.6
According this table the Consumer Price Index was 164.3 in January 1999 and it increased to
216.678 by January 2010. The increase during the 10 years period is: 216.678/164.3 = 1.319.
The expected increase of the converter cost can be estimated using the increase of Consumer
Price index. The 2 x 25 MW, converter station, with the transformer was $22M, the updated
figure is:
50MW Converter Cost = 1.319 *$ 22M = $29.013 M.
ABBs’ E-mail gives a budgetary price for 138kV AC submarine cable and for the 80kV DC
land and submarine cables. Table 6 gives the ABB provided data in US units. ABB estimated
the 50 MW converters would cost $35M. The converter price escalated very rapidly in the
last 10 years. We used an updated converter price of $29M for the 50MW converters in our
price estimation, which is a conservative approach. We also increased the submarine cable
cost to be consistent with other manufacturers.
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Table 6 ABB Provided Cost Data
Using the updated data converter data and the adjusted line data, the Hybrid system cost was
estimated and presented in Table 7 and Table 8.
Table 7Hybrid systems with HVDC light, Alternative 1:69 kV and 138 kV transmission
lines and 80 kV DC submarine cable
Hybrid System with 69 kV Line, Alternative 1
Description
Number of miles
or number Cost per mile in $Total cost $
69kV AC Transmission Line- Double Circuit 5.0 750,000$ 3,750,000$
69kV AC UG Land Cable- Tunnel 2.0 2,300,000$ 4,600,000$
69kV AC HD Transmission Line- H Frames 16.4 1,100,000$ 18,040,000$
138kV AC Transmission Line- Single Pole 50.0 600,000$ 30,000,000$
138kV AC Submarine Cables- Duncan Canal 2 5,600,000$ 11,200,000$
138kV AC Kake Substation and Petersburg Tap 1 2,600,000$ 2,600,000$
IGBT 80kV Converter, Filter, Transformer 2 29,013,000$ 58,026,000$
80 kV DC Submarine Cable- Chatham Strait 41.1 1,191,120$ 48,955,032$
Total 177,171,032$
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Table 8 Hybrid system with HVDC light, alternative 2:138 kV transmission lines and 80
kV DC submarine cable, 80 kV
Hybrid System with Land Cable, Alternative 2
Description
Number of miles
or number Cost per mile in $Total cost $
80kV DC UG Land Cable- Road Access 5.0 1,000,000$ 5,000,000$
80kV DC UG Land Cable- No Road 18.4 1,800,000$ 33,120,000$
138kV AC Transmission Line- Single Pole 50.0 600,000$ 30,000,000$
138kV AC Submarine Cables- Duncan Canal 2 5,600,000$ 11,200,000$
138 kV AC Kake Substation and Petersburg Tap 1 2,600,000$ 2,600,000$
IGBT 80kV Converter, Filter, Transformer 3 29,013,000$ 87,039,000$
80 kV DC Submarine Cable- Chatham Strait 41.1 1,191,120$ 48,955,032$
Total 217,914,032$
The comparison of the data in the Tables shows that Alternative 2 with the land cable is
significantly more expensive than Alternative 1 with the 69kV line.
2.4 Multi-Terminal DC System
The multi-terminal system contains DC transmission lines and submarine cable, rated to
50MW. The converters are connected in parallel to the line. The selection of converters
matching the local maximum load is not practical. According ABB the purchase of four
80kV, 50 MW converters may be feasible but different lower rated units are prohibitively
expensive. The smallest unit that ABB offers at 80kV is the M1 converter that is rated to
109MW.
2.4.1 Multi-Terminal DC System Alternative 1
The multi terminal DC eliminates potential transients and steady state transient stability
problems. The voltage drop in the DC system is less than a comparable AC system because
of the lack of inductive components in the DC line.
Figure 25 shows the conceptual connection diagram of the proposed system.
Sitka
Takatz
Hydro
Kake
Petersburg
DC Submarine Cable
41.1 mi
69kV
AC
69kV
AC 138 kV
AC
DC line
21.1 mi
DC line
44.3mi
28MW
69kV
Figure 25 Multi-Terminal DC Transmission System.
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The DC line is rated 80kV and would be built with four (4) converters rated 50 MW each.
The maximum load current at 80kV voltage between the terminals is 625A.
The existing 69kV AC transmission line design used in Sitka can be converted to 80 kV DC
by removing the insulator and conductor in the middle. The voltage between the conductors
would be 80kV.
The City of Sitka’s 69 kV lines are built with 336.4 kCM 26/7 ACSR "Linnet” conductors.
The thermal rating of the Linnet conductor is 537A. The 625A converter current requires a
larger conductor for the DC line. The 477 kCM “Flicker” conductor rated 670A is suitable
for this DC application.
Figure 23 shows the typical tower of the 69 kV H-frame line used in Alaska. This is a
wooden tower with MacLean S1 series suspension (composite) insulators; the catalogue
number is: S148040VX06. The technical specification of this insulator is listed in Table 6.
Figure 26 shows the S1 composite insulator.
Figure 26 The S1 composite insulator
(Copy from MacLaen Catalouge)
Table 9 Technical Specification of MacLaen Composite Insulators. (Copy from MacLaen
Catalogue)
Catalog
Number Line Voltage Section
Length (in)
Dry
Arc
(in)
Leakage
(in)
Dry Electrical
Flashover (kV) 60
Hz
Wet Electrical
Flashover (kV) 60
Hz
CIFO+
(kV)
Neg Electrical
Flashover (kV)
CIFO
Weight
Ea (lbs)
S148040VX33 69 40.0 29.9 47.7 299 270 519 556 6.5
S148040VX06 69 40.0 29.9 70.9 299 270 519 556 8.3
S148040VX21 69 40.0 29.9 90.3 299 270 519 556 9.8
S148048VX24 115 48.0 37.9 78.9 375 338 648 690 8.6
S148048VX02 115 48.0 37.9 121.5 375 338 648 690 11.9
S148048VX11 115 48.0 37.9 140.9 375 338 648 690 13.9
S148052VX39 115 52.0 42.9 79.1 413 372 712 756 8.4
S148052VX36 115 52.0 42.9 117.8 413 372 712 756 11.4
S148052VX37 115 52.0 42.9 144.9 413 372 712 756 14.0
S148060VX35 138 60.0 49.9 94.8 490 437 837 886 9.3
S148060VX04 138 60.0 49.9 141.2 490 437 837 886 12.9
S148060VX36 138 60.0 49.9 172.2 490 437 837 886 15.
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The peak AC line to ground voltage on a 69 kV line insulator is:
The dry and wet flashover voltage of the insulator is larger than 270kV. The leakage distance
is 70.9 inches. The voltage stress on the S148040VX06 insulator is:
Table 10 gives the IEC 515 recommendation for “specific creapage distance” at different
pollution levels. The creapage distance is the reciprocal value of the voltage stress. The
creapage distance of the S148040V06 insulator used in the typical 69 kV line is:
Table 10 shows that this insulator is suitable to operate under very heavy pollution conditions
because its creapage distance is longer 31mm/kV.
Table 10 IEC 515 Recommended Creapage Distances for Polluted Insulators. (Copy from
IEC 515)
The table specifies the “specific creapage distance” for standard porcelain insulators. The
pollution performance of composite insulators is better than the standard porcelain insulators.
Consequently, the “specific creapage distance“given in Table 10, provides conservative
leakage distance for composite insulators.
The consensus is that for DC voltage the “specific creapage distance” should be 30% larger
than the same AC voltage. The conversion of the AC line to DC requires the longer specific
creapage distance. The specific creapage distance for heavy pollution and for DC line is:
VLn 1.05 69kV
3⋅41.829 kV=:=
Eins
VLn
Lleakage
41.829kV
70.9in 0.59 kV
in
CreapageAC
70.9in
41.829kV 43.053 mm
kV=:=
CreapageDC 1.3 CreapageAC⋅55.969 mm
kV=:=
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The DC voltage is 80 kV between the two conductors, which implies that voltage to ground
is 40 kV. The required leakage distance for a 40kV DC insulator for heavy pollution is:
CreapageDC_40kV 40kV CreapageDC⋅2.239 m=:=CreapageDC_40kV 88.14 in=
The leakage distance of the insulator used presently for 69kV AC in Figure 23 has only 79in
leakage. Therefore, the DC line must be built with a longer insulator like S148048VX21,
which has 90.3in leakage.
The specification of the DC transmission line is:
Tower: 69 kV wooden towers.
Conductor: 470 kCM “Flicker” ACSR conductor, two (2) conductors on each tower
Insulators: MacLean Composite S1 insulator S148048VX21, two (2) per tower
2.4.2 Multi-Terminal DC System Alternative 2
The feasibility of building a DC cable system instead of using overhead lines should be
investigated. The major advantage is that bad weather, like ice and snow, does not affect the
cables.
The cable connection seems to be attractive for the Sitka-Takatz Lake Hydro run, if an
access road would be built along this route, which permits the “spaced laying” of two 80 kV,
land cables with 400mm2 aluminum conductor, rated 90MW in case of spaced laying. Figure
13 shows the ABB land cable. The cables can be directly buried or placed in a shallow
marked ditch.
The sea cables are the same as described in previously under the Hybrid System.
2.4.3 Budgetary Cost Estimate for Multi-Terminal HVDC Light Systems
Table 11 gives the cost estimates for the two multi-terminal Alternative 1 and Table 12 for
Alternative 2.
Table 11 Cost Estimate for the Multi-Terminal HVDC Light System Alternative 1
Multi-Terminal System- DC Line, Alternative 1
Description
Number of miles
or number Cost per mile in $Total cost $
80kV DC UG Land Cable- Road Access 5.0 1,000,000$ 5,000,000$
80kV DC UG Land Cable- Tunnel 2.0 1,800,000$ 3,600,000$
80kV DC Transmisson Line- H Frames 16.4 840,000$ 13,776,000$
80kV DC Transmisson Line- Single Pole 50.0 420,000$ 21,000,000$
80kV DC Submarine Cable- Duncan Canal 2 4,000,000$ 8,000,000$
69kV AC Kake Substation and Petersburg Tap 1 2,400,000$ 2,400,000$
IGBT 80kV Converter, Filter, Transformer 4 29,013,000$ 116,052,000$
80 kV DC Submarine Cable- Chatham Strait 41.1 1,191,120$ 48,955,032$
Total 218,783,032$
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Table 12 Cost Estimate for the Multi-Terminal HVDC Light System Alternative 2
Multi-Terminal System- DC Cable, Alternative 2
Description
Number of miles
or number Cost per mile in $Total cost $
80kV DC UG Land Cable- Road Access 5.0 1,000,000$ 5,000,000$
80kV DC UG Land Cable- No Road 18.4 1,800,000$ 33,120,000$
80kV DC Transmission Line- Single Pole 50.0 420,000$ 21,000,000$
80kV DC Submarine Cable- Duncan Canal 2 4,000,000$ 8,000,000$
69kV AC Kake Substation and Petersburg Tap 1 2,400,000$ 2,400,000$
IGBT 80kV Converter, Filter, Transformer 4 29,013,000$ 116,052,000$
80 kV DC Submarine Cable- Chatham Strait 41.1 1,191,120$ 48,955,032$
Total 234,527,032$
2.5 AC transmission System with compensated submarine cable
The AC transmission system will be built with 138 kV line between Petersburg and Kake,
138kV compensated submarine cable between Kake and Takatz Lake Hydro and 69kV line
between Takatz Lake Hydro and Sitka.
The transmission lines will be the usual single pole (Kake) or H-frames (Sitka) with wooden
poles with composite suspension insulators.
ABB proposed a new 138 kV submarine cable shown in Figure 16. The cable total charging
current is more than 800A at 138kV, which is larger than the load current. The proper
operation of the AC system requires the compensation of capacitive charging current by
inductances. Figure 27 shows the connection diagram of the AC three phase version of the
intertie.
Figure 27 Three phase AC transmission system
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2.5.1 Analysis of the Three Phase AC Intertie Operation
The selection of the compensating reactors requires the analysis of the system operation at
full load 50MW and no load or at light load 1-5 MW. Compensating reactors will be placed
both at the Kake and the Takatz Lake terminals. The system one line equivalent circuit is
shown in Figure 28.
AC AC
AC submarine Cable 138kV 41.1 mi69kV LINE 21.1 mi
Sitka 22 MW
69 kV AC
138 kV LINE 44.3 mi
Petersburg 50MW
138 kV AC
AC
Takatz Hydro
28MW
Compensating
reactance
Compensating
reactance
1234567
Figure 28 Equivalent circuit for the Three phase AC transmission system
For the analysis the worst case is assumed, when Sitka and Takaz Lake Hydro supplies 50
MW to Petersburg through the submarine cable and transmission line. Therefore, Takatz
Lake Hydro supplies 28MW and Sitka supplies 22MW through a 69kV line.
The 50 MW, pf=0.8 load was connected to the Petersburg terminal; the 138 kV line between
Petersburg and Kake is represented by a T circuit; the 138kVsubmarine cable is divided into
three (3) sections and represented π circuits connected in series. A compensating reactor is
connected between the phase conductor and ground at both side of the submarine cable. The
138kV/69kV transformer is represented by an ideal transformer and its leakage reactance
connected in series. The Takatz Lake Hydro is represented by an ideal generator, series
impedance (R and L) represents the 69 kV line between Takatz Lake and Sitka. The data
used for the analysis is listed in Table 13.
Table 13 Data for Operation Analysis
The operation analysis calculated the voltage and current at each section. The calculation
started at the Petersburg terminal. The load current was calculated first, this will be the
current in section 1-2. This is followed by the calculation of the voltage at node 2 using the
load current. The capacitive current was calculated using the voltage at node 2. The current
between nodes 2-3 is the sum of the capacitive current and the current between nodes 1-2.
This procedure has been followed to determine the voltage at each node and the current in
each section. The sample calculation is shown in Appendix 1.
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The requirement is that the voltage drop must be less than 10% at maximum load at nodes
with loads, less than 15% is acceptable for the other nodes and the current must be less than
the specified maximum section current, which is around 550A.
The calculation was performed at full load and at no load. The compensation has been varied
until acceptable results were obtained.
The results at full load with 0.5H and 0.55H compensation reactance at the terminals of the
submarine cable are:
The results shows that the voltage drop on node 1,2, 6 and Sitka is less than 4%. The line
current is less the 400A. This is a very acceptable operation condition.
The result at no load with 0.4H and 0.35H compensation reactance at the two terminals of the
submarine cable are:
The result shows that the voltage drop is less than 2%. The line current is less the 400A. This
is a very acceptable operation condition.
Accordingly, the proper operation requires two adjustable reactance with inductance
adjustable 0.3-0.6 H.
ABB offers a 3-phase VSR at 138 kV nominal voltages with regulating range of 60-35
MVAR. Very rough price estimation for this VSR is 2-2.3 MUSD per unit in a standard
design for ABB Ludvika and delivered to US port. General delivery time is in the range of
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11-13 months after order. Of course, there would be added costs for state and local sales/use
taxes, civil works, installation, local transport to sites, associated circuit breakers/switches,
protection etc.
2.5.2 Budgetary Cost Estimate Three Phase AC System
Table 14 gives the cost estimates for the three phase AC version of the intertie.
Table 14 Cost Estimate for the AC Transmission System
138kV AC System
Description
Number of miles
or number Cost per mile in $Total cost $
69 KV AC Transmission Line- Double Circuit 5.0 750,000$ 3,750,000$
69/138kV 50 MVA Substation- Bear Cove 1
138kV AC UG Land Cable- Tunnel 2.0 2,400,000$ 4,800,000$
138kV AC HD Transmission Line- H Frames 16.4 1,200,000$ 19,680,000$
138/69kV AC Takatz Powerhouse Conversion 1 500,000$ 500,000$
138kV AC Circuit Breaker at Landfall-SCADA 1 1,500,000$ 1,500,000$
138kV AC Transmission Line- Single Pole 50.0 600,000$ 30,000,000$
138kV AC Submarine Cables- Duncan Canal 2 5,600,000$ 11,200,000$
138kV AC Kake Substation and Petersburg Tap 1 2,600,000$ 2,600,000$
Reactance 138kV, 550A, 2 2,300,000$ 4,600,000$
138kV AC Submarine Cable- Chatham Strait 41.1 1,494,032$ 61,404,715$
Total 140,034,715$
2.6 Summary of the Comparison of Different Systems
The cost comparison of the different systems is presented in Table 15. It can be seen that the
most economical system is the three phase AC system with compensated submarine cable.
Table 15 Cost Comparison of Different Systems
Cost comparizion
138kV Three phase AC System 140,884,715.20$
Multi-Terminal System- DC Line, Alternative 1 218,783,032.00$
Multi-Terminal System- DC Cable, Alternative 2 234,527,032.00$
Hybrid System with 69 kV Line, Alternative 1 177,171,032.00$
Hybrid System with Land Cable, Alternative 2 217,914,032.00$
Table 15 shows that the ABB proposed three phase system with the compensated submarine
cable is the most economical system. This alternative was not considered in the last study
because the literature advised that AC cables longer than 30-40 miles are not advisable.
Obviously, ABB experience proved the feasibility to extend the range of AC submarine
cables using inductive compensation. The presented calculation clearly shows that the usual
138kV, three phase system with reactance compensated submarine cable is a technically
feasible and economical solution for the Southeast Alaska intertie.
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The market changed in the last 10 years and the cost of DC land cable and converters
increased significantly. ABB proposed 50MW, 80 kV converters with an estimated cost of
$35M, which means $700,000/MW or $700/kW.
Another market change is that the manufacturers are not interested in building small HVDC
Light or HVDC Plus systems. Indian and Chinese markets as well as the European offshore
wind farms demand large, several hundred megawatt ratings for the voltage source based
HVDC systems. The manufacturers are working on large IGBT based HVDC systems which
can compete with the classical thyristor based HVDC and suitable to form DC networks.
From a technical point of view, the HVDC Light system is superior to the classical HVDC
system. The major advantages are multi-terminal operation, weak-system tolerance, black
start capability, and reactive power control. The authors of this report believe that the multi-
terminal approach is the technically most beneficial. Unfortunately, this system is the most
expensive. The technical advantages do not compensate for the high cost.
Another surprise is that the costs of land cable became significantly higher than a simple AC
line cost. ABB’s attitude changed. The enclosed E mail recommends the land cable if the
building of an overhead line is not permitted.
The recommended three phase AC system losses per mile are the same as the losses on the
rest of the 138kV Alaska system.
The maintenance of the AC system is the same as the present system maintenance. The
submarine cable does not need special maintenance and the compensating reactors are similar
to a transformer.
3 Conclusions
The investigations show that the Sitka-Kake-Petersburg intertie should be built with as a
standard three phase 138kV system with 138kV reactance compensated submarine cable. All
components, except for the compensating reactances, are standard well proven products. The
compensating reactances are similar to a transformer.
The voltage source converter based HVDC Light or HVDC Plus system has technically
advantages but the technical advantages do not compensate for the high cost. The
manufacturers do not recommend the HVDC Light or HVDC Plus system for 50 MW.
4 References
[1] www.abb.com/hvdc
[2] siemens.com Global Website
[3] HVDC & SVC Light- Reference list;
http://www05.abb.com/global/scot/scot267.nsf/veritydisplay/5d0bb83bb5e3a0078525
72e500540f9d/$File/HVDC%20and%20SVC%20Light%20web.pdf
[4] Niel Kirby: AREVA T&D Power Electronics-HVDC & FACTS, araeva.pdf
[5] HVDC Light® Power Cables.pdf, Brochure ABB’s high voltage cable unit in
Sweden. www.abb.com/cables
Southeast Alaska HVDC System Report 6-Draft 3-10-11.docx
48 07/21/11
[6] Leif Englund, Mark Lagerkvist, Rebati Dass:”HVDC superhighways for China, ABB
Review, 14, 4/2003
[7] Michael Bahrman: “HVDC Transmission. Panel session, Atlanta Novembr 1, 2006
[8] W.Breuer,D. Povh, D. Retzmann, E. Teltsch,X. Lei: “ Role of HVDC and FACT in
future Power System”; CEPSI, 2004, Shanghai.
[9] M. Mohaddes, D. P. Brandt, M.M. Rashwan, K. Sadek, “Application of the Grid
Power Flow Controller in a Back-to-Back Configuration”, [CIGRE Report B4-307,
Session 2004]
[10] Chan-Ki Kim, Young-Hun Kwon, Gilsoo Jang:”New HVDC Interaction between AC
network and HVDC Shunt Reactor on Jeju Converter Station, IEEE Trans. on Power
Delivery, Vol 22, No3. July, 2007
[11] Chandana Karawita, Udaya D. Annakkage: ”Multi-Infeed HVDC Interaction Studies
Using Small-Signal Stability assessment”; , IEEE Trans. on Power Delivery, Vol.24,
No2, April. 2009
[12] 1ZSE 954901-19_Application Buyers Guide SR_Rev Aug 2 2009, ABB WEB site
[13] The Okonite Submarine Cables and Product:
http://www.okonite.com/Product_Catalog.html
[14] Submarine Cables and Projects: http://www.abbcables.com/sub.html
5 Bios sketches
George Karady (SM'70, F'78) received BSEE and Doctor of Engineering degree in
electrical engineering from Technical University of Budapest in 1952 and 1960, respectively.
Dr. Karady was appointed to Salt River Project Chair Professor at Arizona State University
in 1986, where he is responsible for the electrical power education and performs research in
Power Electronics, High Voltage Techniques and Electric Power. Previously, he was with
EBASCO Services where he served as Chief Consulting Electrical Engineer. He was
Electrical Task supervisor for the Tokomak Fusion Test reactor project in Princeton. He
worked for the Hydro Quebec Institute of Research as a Program manager. Between 1952-
1969 he worked for the Technical University of Budapest where he progressed from Post
Doctoral Student to Deputy Department Head.
Dr. Karady is a registered professional engineer in New York, New Jersey and Quebec. He
is the author of more than 100 technical papers.
Dr. Karady is the chairman of IEEE WG on Non-Ceramic Insulators and WG on Insulation
Coordination. He is a member of the CIGRE U.S. Technical Committee. Dr. Karady served
in the US National Committee of CIGRE as Vice president and secretary treasurer. In 1996
Dr. Karady received an Honorary Doctor Degree from Technical University of Budapest.
Mr. Mike Carson earned a B. S. degree in electrical engineering and is a registered
electrical engineer in Alaska, Washington, Oregon and California. He has over 40 years of
experience in the planning, designing and engineering of transmission and distribution
systems for small utilities such as cooperatives, municipalities, public utility districts and
Southeast Alaska HVDC System Report 6-Draft 3-10-11.docx
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government agencies. His system planning experience includes system design, preparation of
long range and construction work plans, life cycle analysis of alternatives, evaluation of
losses and conversion of systems to higher voltages. Mr. Carson has over 18 years of
experience working on engineering projects in Alaska. He is the owner of Northstar Power
Engineering and has been a resident of Southeast Alaska since 1992.
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Appendix
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