Transmission planning in
Vermont
Past, present and future
Docket 7081 workshop
By Dean LaForest
9/19/05
What is transmission planning?

Transmission planning examines the need for
changes to the transmission network as load and
power sources change through time in an area

The transmission network consists of all electric
transmission lines and substations, typically built and
constructed at 115,000 volts or above


Vermont has an underlying subtransmission network with
significant facilities built and operated at 34,500 and 46,000
volts that often parallel the transmission network
VELCO owns and operates the transmission grid in Vermont,
while the Vermont distribution companies own and operate the
subtransmission network
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What tools and key sets of data are needed
and necessary for transmission planning?


Need software to model the behavior and performance
of the power system
Need accurate model of the power system to capture
existing system performance and predict future system
performance



Model needs input on network characteristics (t-lines /
transformers), reactive power sources (generators / caps / sync
condensers / FACTs devices), real power sources (generators /
HVDC), and loads
Model needs sets of this data for each condition examined (load
level / generation dispatch, etc.
Need a set of reliability standards against which to
measure the system performance and determine
whether reinforcements are needed
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What are VELCO’s sources for these sets
of tools / data?



VELCO uses a widely utilized power flow analysis
software, allowing high productivity and data
interrogation capabilities
VELCO provides modeling information for the power
system network to ISO-NE, who collects information
from the rest of New England and the eastern US /
Canada
VELCO gets load information from the distribution
companies and the DPS for VT, and from the
database provided by ISO-NE for areas outside of
VT
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What are the regional reliability standards?

NERC (North American Electric Reliability Council)



Standards found on NERC website
(http://www.nerc.com/~filez/standards/Reliability_Standards
.html#Transmission_Planning)
These are the minimum level of standards the system must
meet
NPCC (Northeast Power Coordinating Council)


Standards found on NPCC website
(http://www.npcc.org/criteria.asp)
New England by way of the ISO-NE reliability standards is
and must be compliant with these criteria, which are more
specific than NERC’s criteria
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What are the regional (NPCC) reliability
standards?
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What are the New England (ISO-NE)
reliability standards?


ISO-NE’s planning criteria are located at
http://www.isone.com/rules_proceds/isone_plan/index.html
Planning Procedure #3 is the key document
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Reliability Standards Evolve


NERC’s Standards will be more stringent,
become mandatory, and will include penalties
The FERC will put in place an ERO – and
Energy Reliability Organization
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The type of system under study matters

Vermont system characteristics






Importer of electrical power
Two large sources relative to the load
Minimal reserves
Winter and Summer peaking
Sparse transmission network
Located at one end of the New England system
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Planning design example . . . the problem


Question – feed 50 MW of load (Addison county)
from a 50 MW generator (McNeil) 40 miles away
Choices

46 kV line (can look like a distribution circuit)




Single conductor
Double conductor
115 kV line (standard VELCO h-frame)
The issues


Provide adequate voltage for customers (within 5% of
nominal)
Provide coverage for expected outages
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The first test . . . Can 46 kV work?
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The first test . . . Can 46 kV REALLY
work?
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The first test . . . Can 46 kV work with two
conductors (or bundled conductors)?
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40 miles . . .
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The second test . . . Can 115 kV work over
40 miles?
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To meet a N-1 design standard (be able to
suffer the loss of one element) . . .
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VELCO’s design standard for
transmission planning . . .


Conforms to NERC, NPCC and ISO-NE planning
standards
We consider the unavailability of system elements that
have potential long duration outages (more than one
load cycle)





Highgate DC converter
Underground (or underwater) cables
Transformers
Generators
After system adjustment following first outage, VELCO
tests all other potential outages
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What has VELCO done in the past for
long range transmission planning

VELCO’s recently performed long range studies
include the “Twenty Year Plan” (1987), the “Long
Range Transmission Plan” (1992), and “A Strategic
Planning Study” (2001)




Each considered, and included, distribution company
projects / plans and current regional system information
Each effort used the latest tools and system models
available
The earlier two efforts included examination of power
source location and its influence on transmission expansion
Each effort built on the past using better tools, and utilized
a more thorough understanding of the transmission
network (with less predictable performance as time went
on).
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What VELCO projects included analysis
of future system performance?

Those projects included the Essex
STATCOM (filed June 1999 – docket 6252),
the Rutland Region Reliability Project (filed
March 2001 – docket 6479), the Northern
Loop Project (filed December 2002 – docket
6792) and the Northwest Reliability Project
(filed June 2003 – docket 6860)
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What peak loads did VELCO experience
during these planning efforts?
Vermont seasonal peaks
1100
1050
1000
950
VT load
900
850
max sum
max win
800
750
700
650
600
550
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
1980 to 2005
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What will VELCO provide to comply with
Act 61?


VELCO will perform a study examining system performance 10
years from the present (i.e. 2015). The analysis will likely
consider:
 All facilities available, and with one facility out due to a long term
outage
 Stressed transfer conditions
 The continued availability of energy from Highgate and how it
might influence transmission system design
 A reduced load growth scenario and how that might influence the
timing of transmission system reinforcements
 Proposed in-state generation projects and how they may
influence transmission system design
VELCO will provide a draft report early in 2006 and hold public
meetings to promote discussion and elicit comments before
publishing a final report by July 1, 2006
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What activities will take place within the
Long Range Planning process?



Involve the Vermont distribution companies (via the Vermont
Utility Planning Group) in review of interim results and proposed
solutions
 Make certain that distribution utility issues / projects are
considered and properly reflected in the analysis
Involve ISO-NE through collaborative meetings to review results,
refine modeling of beyond Vermont conditions / assumptions and
provide / seek input on the transmission system design
necessary to address system deficiencies that do not meet
design criteria
Propose a series of alternatives to any discovered system wide
deficiency

Provide planning grade cost estimates for the alternatives to
allow ranking
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Questions?
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A probabilistic reliability guideline for
subtransmission planning, based on the
equal slope criterion
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Conceptual Cost-Benefit Map
C
benefits
B
A
Diminishing returns on
investment
costs
Figure 1
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Conceptual Cost-Benefit Map
C
A
Total benefit similar to option C
benefits
Total cost similar
to option A
B
desired tradeoff occurs
near "knee" of curve
"Most for Less"
Planning Philosophy
costs
Figure 2
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Equal Slope Criterion
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