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Transmission Enhancement Technology Report
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EXECUTIVE SUMMARY
Western Area Power Administration (Western), was directed to conduct a study
pursuant to the following language in House Report 107-148, the Conference
Report for the Supplemental Appropriation Act, 2001, Pub. L. 107-20, :
“Non-reimbursable funding of $250,000 is provided to conduct a planning study
of transmission expansion options and projected costs in Western’s Upper Great
Plains Region. Existing Western transmission capacity is insufficient to support
the development of known energy resources that could support new electric
generation capacity in the Upper Great Plains Region. The directed study will
require assumptions as to future generation locations. Western is directed to
solicit suggestions from interested parties for the sites that should be studied as
potential locations for new generation and to consult with such parties before
conducting the study. Western is directed to produce an objective evaluation of
options that may be used by all interested parties.”
Additionally, House Report 107-258, the Conference Report for the Energy and
Water Development Appropriations Act 2002, Public Law 107-66, states, “Within
the amount appropriated, not less than $200,000 shall be provided for the
Western Area Power Administration to conduct a technical analysis of the costs
and feasibility of transmission expansion methods and technologies. These
funds shall be non-reimbursable. Western shall publish a study by July 31, 2002
that contains a recommendation of the most cost-effective methods and
technologies to enhance electricity transmission from lignite and wind energy. “
INTRODUCTION
There have always been challenges associated with moving large amounts of
power over a transmission system, however, recent requests for transmission
service has resulted in new limitations of the system because of the desire to buy
and sell energy into different market locations. This has resulted in heavy
transmission utilization in certain areas that was not considered when the system
was initially constructed. This has also increased the need for improvements in
transfer capability while maintaining the historically high level of reliability. These
improvements must be done in a cost-effective manner, however. This challenge
has increased interest in creating a more robust power system through the use of
new technologies applied to the existing grid.
Western continually evaluates new and better practices to improve system
operation and optimize and increase the use of the transmission system. All new
technologies are evaluated on a case-by-case basis and are used when the new
technology is cost effective and can provide benefits to the system.
The purpose of this report is to summarize and compare "newer" technologies
with some of the existing technologies and methods used to increase
transmission capability. Section 3 documents existing technologies used in the
industry today. Section 4 involves discussion of new technology to improve
existing equipment. Section 5 describes some of the new transmission
equipment technologies with potential to improve transmission capability.
Section 6 documents recent research into practices to more efficiently use
different aspects of the existing system. Finally, Section 7 summarizes those
technologies that have potential application to the Western's Upper Great Plains
Region transmission needs.
EXISTING TRANSMISSION IMPROVEMENT METHODS AND
TECHNOLOGIES
When improvements and additions to the transmission system have been
required in the past, several methods to increase Available Transmission
Capability (ATC) have been used. This section discusses the traditional types of
design alternatives used by Western and the electric industry.
The primary system improvements involve upgrades or replacements to the
existing transmission lines, or installation of new transmission lines. Typically
when more power carrying capability is required between areas in the power
system, several traditional options exist for providing this increase in
transmission capability.
IMPROVED UTILIZATION OF EXISTING TRANSMISSION
Economic concerns and limitations on obtaining new right-of-ways for
transmission lines have greatly increased the need for additional power transfer
on the existing equipment. As a result, a number of new technologies for
increasing the short-term capacity of lines and transformers are being developed.
Because the facility rating may be higher for only a short period, the new
technologies below will allow for increased transmission capability, however, it
will be Non-Firm or interruptible capability. Non-Firm ATC may not be beneficial
for incorporating new generation into Western's system, as typically the
generator owner requests Firm or non-interruptible ATC.
Typically, the amount of clearance between energized conductors and other
objects limits the capacity increase of most existing overhead transmission lines.
As the load on a line increases, the temperature of the conductor increases
causing the conductor to elongate. The increased elongation results in additional
“sag” in the conductor, thereby reducing the clearance to other conductors and
objects. The amount of sag for a given current loading is directly affected by the
weather conditions including ambient temperature and wind speed.
POTENTIAL NEW EQUIPMENT TO IMPROVE TRANSMISSION
CAPABILITY
Although upgrades to existing equipment may require a smaller capital
investment than installing new equipment, upgrades to existing equipment still
has its limitations based on the age of the equipment and the technology being
considered. Therefore, research emphasis has been put into developing
improved new equipment to increase the transfer capability of the power system.
This new equipment can be separated into three categories: transmission lines,
substation equipment, and generation station equipment
Transmission:
Research for improvements to transmission lines has primarily focused on a new
conductor called Aluminum Conductor Composite Reinforced (ACCR). This
conductor can operate at three times the ampacity of Aluminum Conductor Steel
Reinforced (ACSR) conductor and has a much higher heat rating, but doesn't
weigh as much. Western is participating in a pilot project with 3M to field test this
new conductor on its Jamestown – Fargo 230 kV line in North Dakota.
“ACCR conductor is probably going to be marketed as a replacement for ACSR
conductors in areas were electrical loading has to be increased. ACCR can be
installed without changing out structures because of the higher current carrying
capacity. v” This new conductor would allow the use of existing towers and rightof-
way decreasing installation costs. This conductor will likely not be
commercially available until late 2003 depending on field test results. As part of
the project, 3M is preparing a cost-benefit analysis for Western.
Substation Equipment:
There have been a variety of new technologies developed to improve substation
design and modifications. Emphasis has been directed towards monitoring and
controlling substations. Projects such as Power Systems Monitoring Using
Wireless Subs look at the possibility of cost savings by transmitting internal
substation data using spread spectrum radio waves. “This project will
demonstrate feasibility and benefits of wireless technology when used for
substation and system-wide applications.” In addition, a new concept of mobile
agents for distributed computer network applications will be demonstrated using
the monitoring applications. Both approaches are to provide cost savings when
implementing the communication systems for monitoring applications.viii” The
project uses multiple data collection points, called mobile agents to transmit data
to a typical personal computer whose data can then be transmitted to a central
station. This wireless concept will ideally decrease the initial cost of substation
wiring.
POTENTIAL NEW PRACTICES TO IMPROVE TRANSMISSION
CAPABILITY
Western has actively supported a new initiative by EPRI, which is documented in
a book entitled Guidebook to Increase Power Flow in Transmission and
Substation Circuits. This guidebook will include topics relevant to new
technologies in increasing power flow in an existing system. The goal of the
book as stated by EPRI is to “increase power flow resulting from the
implementation of best practices on transmission and substation circuit
components.x”
Fault locating is a critical aspect of power system reliability and delivery. When a
fault occurs, the sooner it is located, the sooner the transmission line can be
restored to service. PSERC is currently working on a project for TVA, with
Western funding, and is planning to release the results to all members in report
entitled Fault Location Using Sparse Data and Wireless Communications for
Collection of PQ Data in the TVA System. The project goal is to “develop new
algorithmic and concepts for on-line monitoring of the power system conditions
where better accuracy and faster response are possible.xi” Another goal of the
project is to “make the use of the data recorded by both Diver’s and PQ meters
readily accessible to the users in a more efficient way.xii” With the current
changes taking place in the power industry, there is a need for a more stable
power system with the increasing complexity of planning in a dynamically
changing environment. PSERC has begun a project called Robust Control of
large-scale Power Systems. “This project seeks to apply modern robust control
methods to analyze and design controllers for large-scale power systems,
developing algorithms that remain tractable in these high dimensional
applications.
APPLICABILITY OF NEW TECHNOLOGIES
Western is committed to finding the most economical means to upgrade and
operate the transmission system reliably. Western will continue to evaluate new
technology and better practices in its design, construction, maintenance, and
operating philosophies. New technologies may be considered for new
transmission facilities if they are technically viable, are found to be cost effective,
and can provide a benefit to the transfer capability of the system.
The technologies that have been presented in this report represent possible
solutions to a variety of issues facing the power industry. However, most of
these technologies are not yet commercially viable and may be only temporary
solutions to problems. Others require investments not directly related to current
problems, but that may lead to future cost savings. Very few of the new
technologies for which Western has provided research development monies can
be used in projects identified in the "Montana-Dakotas Regional Transmission
Study". The application of some of the technologies that might be considered is
discussed below.
All aspects of dynamic line rating are a possibility for increasing the real-time
loading of Western's transmission system to accommodate increased Non-Firm
transmission utilization. As noted earlier, application of dynamic line ratings does
not generally allow for increased Firm ATC, and system additions are generally
required to provide increased Firm transmission capability.