IESO_PRO_0728
PUBLIC
Market Manual 7: System Operations
Part 7.12: Available
Transfer Capability
Implementation
Document
Issue 3.0
This document explains how the TTC and the ATC
are calculated at the IESO.
Public
Disclaimer
The posting of documents on this Web site is done for the convenience of market participants and
other interested visitors to the IESO Web site. Please be advised that, while the IESO attempts to have
all posted documents conform to the original, changes can result from the original, including changes
resulting from the programs used to format the documents for posting on the Web site as well as from
the programs used by the viewer to download and read the documents. The IESO makes no
representation or warranty, express or implied, that the documents on this Web site are exact
reproductions of the original documents listed. In addition, the documents and information posted on
this Web site are subject to change. The IESO may revise, withdraw or make final these materials at
any time at its sole discretion without further notice. It is solely your responsibility to ensure that you
are using up-to-date documents and information.
This document may contain a summary of a particular market rule. Where provided, the summary has
been used because of the length of the market rule itself. The reader should be aware, however, that
where a market rule is applicable, the obligation that needs to be met is as stated in the “Market
Rules”. To the extent of any discrepancy or inconsistency between the provisions of a particular
market rule and the summary, the provision of the market rule shall govern.
Document ID
IESO_PRO_0728
Document Name
Part 7.12: Available Transfer Capability Implementation Document
Issue
Issue 3.0
Reason for Issue
Incorporated into Market Manual 7.0 for Baseline 27.1
Effective Date
June 6, 2012
Part 7.12: Available Transfer Capability Implementation Document
Document Change History
Document Change History
Issue
Reason for Issue
Date
1.0
First release
February 10, 2011
2.0
Changes to Sections 5, 6 and 7
February 22, 2012
3.0
Issue released for Baseline 27.1
June 6, 2012
Related Documents
Document ID
Document Title
IESO_PRO_0729
Market Manual 7.11: Transmission Reliability Margin Implementation
Document
IMP_POL_0002
Market Manual 7.4: IESO Controlled Grid Operating Policies
Issue 3.0 – June 6, 2012
Public
Part 7.12: Available Transfer Capability Implementation Document
Table of Contents
Table of Contents
Table of Contents ...................................................................................................... i
List of Tables ............................................................................................................ ii
Table of Changes .................................................................................................... iii
1.
Introduction.................................................................................................... 1
1.1
1.2
Reliability Standards Addressed in this Procedure ..................................................... 1
Acronyms Used in this Procedure ............................................................................... 1
2.
Total Transfer Capability .............................................................................. 3
2.1
2.2
Computing Total Transfer Capability ........................................................................... 3
2.1.1 Base Case ....................................................................................................... 3
2.1.2 Pre-contingency Criteria .................................................................................. 4
2.1.3 Post-contingency Criteria ................................................................................ 4
2.1.4 Contingencies .................................................................................................. 4
2.1.5 Outages ........................................................................................................... 4
2.1.6 Counterflows and Expected Interchange......................................................... 4
Publishing Total Transfer Capability ........................................................................... 5
3.
Available Transfer Capability ....................................................................... 6
3.1
3.2
Computing Available Transfer Capability .................................................................... 6
Publishing Available Transfer Capability ..................................................................... 6
4.
Background Information ............................................................................... 7
4.1
4.2
Transmission Service in Ontario ................................................................................. 7
ATCID NERC Definitions ............................................................................................ 7
References ................................................................................................................ 1
Issue 3.0 – June 6, 2012
Public
i
List of Tables
IESO_PRO_0728
List of Tables
Table 1-1: NERC Standards Applicable to Available Transfer Capability ............................... 1
Table 1-2: List of Acronyms .................................................................................................... 1
Table 4-1: ATCID NERC Definitions ....................................................................................... 7
ii
Public
Issue 3.0 – June 6, 2012
Part 7.12: Available Transfer Capability Implementation Document
Table of Changes
Table of Changes
Reference
(Section and
Paragraph)
Entire
Document
Description of Change
Incorporated into Market Manual 7.0: System Operations as Part 7.12.
Issue 3.0 – June 6, 2012
Public
iii
Part 7.12: Available Transfer Capability Implementation Document
1.
1. Introduction
Introduction
The IESO is responsible for reliably operating the Ontario Bulk Electric System. We facilitate the
wholesale energy market and schedule imports and exports across each of Ontario’s external interfaces,
which include ties to New York, Michigan, Quebec, Minnesota, and Manitoba.
The Available Transfer Capability Implementation Document (ATCID) was created in compliance with
NERC standard MOD-001-1a: R3. The ATCID describes the methodology used by the IESO to compute
the Total Transfer Capability (TTC) and Available Transfer Capability (ATC) for Ontario’s external
interfaces, as part of the IESO’s responsibilities as a Transmission Service Provider (TSP) and a
Transmission Operator (TOP) in the province of Ontario.
1.1
Reliability Standards Addressed in this Procedure
In compliance with NERC standard MOD-001-1a: R1 which requires all TOPs to select a methodology
for calculating ATC, the IESO has chosen to adopt the standard MOD-029-1a: Rated System
Methodology. .
Table 1-1: NERC Standards Applicable to Available Transfer Capability
Standard ID
Title
MOD-001-1a
Available Transmission System Capability
MOD-029-1a
Rated System Path Methodology
1.2
Acronyms Used in this Procedure
Table 1-2: List of Acronyms
Acronym
Definition
ATC
Available Transfer Capability
ATCID
Available Transfer Capability Implementation Document
CBM
Capacity Benefit Margin
DSO
Dispatch Scheduling and Optimization
ERAG
Eastern Interconnection Reliability Assessment Group
ETC
Existing Transmission Commitment
LSE
Load-Serving Entity
MMWG
Multi-regional Modeling Working Group
NERC
North American Electric Reliability Corporation
Issue 3.0 – June 6, 2012
Public
1
1. Introduction
IESO_PRO_0728
Acronym
Definition
SAA
System Adequacy Assessment
SS-37
System Studies-37
SSR
System Status Report
TOP
Transmission Operator
TRM
Transmission Reliability Margin
TSP
Transmission Service Provider
TTC
Total Transfer Capability
– End of Section –
2
Public
Issue 3.0 – June 6, 2012
Part 7.12: Available Transfer Capability Implementation Document
2. Total Transfer Capability
2. Total Transfer Capability
Total Transfer Capability (TTC) is the amount of electric power that can be transferred over an
interconnection in a reliable manner while meeting all of specific set of defined pre and post
contingency system condition. This transfer capability depends on generation dispatch, system load
level, load distribution in the network, power transfer between areas, and the limits imposed on the
transmission system due to thermal, voltage, and stability consideration. These limits are determined
for one or both directions of flow, as necessary.
2.1
Computing Total Transfer Capability
NERC Standard
MOD-029-1a: Rated System Path Methodology, R1, R2, R3, R4
Generally, the transmission interface limits are computed to satisfy pre- and post-contingency criteria
considerations, such as:
• Steady state damping stability and damping factor,
• Line and equipment loading must not exceed their ratings,
• Relay margins are within defined bounds,
• Voltage declines must not exceed certain limits,
• Generators must remain in synchronism, AND
• Voltages are stable (V-Q sensitivity is positive).
Details are provided in “IMP_POL_0002 Market Manual 7.4: IESO-Controlled Grid Operating
Policies”, Appendix B.3.2.”
In order to compute a TTC, one often makes a number of assumptions, such as target years, seasons,
load type, statuses of generation, and available transmission facilities as stated in Internal Manual 7.4
Section 5.2.2. The assumptions used in determining a TTC are consistent with those applied when
computing system operating limits. The assumptions used in computing the TTCs are no more
limiting than the assumptions used for planning studies.
2.1.1
Base Case
On an annual basis, the System Studies-37 (SS-37) group develops a library of solved load flow cases
and associated dynamic data and submits them to the Multi-regional Modeling Working Group
(MMWG) under the Eastern Interconnection Reliability Assessment Group (ERAG). MMWG is
responsible for developing and maintaining the library of power flow and dynamic cases.
Regional Coordinators (i.e., NPCC) are responsible for submitting the initial changes to each case of
these cases. The MMWG base cases are an amalgamation of inputs from each of the areas within the
Reliability Coordinators footprint. The IESO base cases include external system models and data
from the MMWG case. The base case generation dispatch for external areas is based on the MMWG
case. The phase shifters are modeled as per what would be expected for the time frame being studied.
There setting and status may be adjusted depending on the specific requirements of the study.
Issue 3.0 – June 6, 2012
Public
3
2. Total Transfer Capability
IESO_PRO_0728
The master base cases include all connection assessment projects that are approved, including those
that did not require a formal connection assessment study. Local area details are added as
appropriate. Information regarding base cases can be found on the IESO's Forecasts webpage.
2.1.2
Pre-contingency Criteria
In deriving the total transfer capabilities, the IESO-controlled grid must meet the pre-contingency
criteria listed in “IMP_POL_0002 Market Manual 7.4: IESO-Controlled Grid Operating Policies”,
Appendix B, section B.3.1.
2.1.3
Post-contingency Criteria
In deriving the total transfer capabilities, the IESO-controlled grid must meet the post-contingency
criteria listed in “IMP_POL_0002 Market Manual 7.4: IESO-Controlled Grid Operating Policies”,
Appendix B, section B.3.2.
2.1.4
Contingencies
The total transfer capabilities shall be calculated based on the contingencies listed in
“IMP_POL_0002 Market Manual 7.4: IESO-Controlled Grid Operating Policies”, Appendix B,
section B.2.
2.1.5
Outages
The following criteria are applied when considering the impact of outages:
• For daily TTC computations, outages more than 15 minutes are included in the TTC.
• For monthly TTC computations, outages more than 7 days are included in the TTC.
• For annual TTC computations, outages more than 30 days are included in the TTC.
For external outages, the TTC may be determined from coordinated studies with neighbouring
jurisdictions and/or operating study reports that state the revised interface limitation.
Information on outages that could impact Ontario’s external interfaces is exchanged with
neighbouring Transmission Owners and/or Reliability Coordinators. Reciprocal agreements are in
place whereby Ontario’s neighbours also provide the IESO with any outage information that would
affect the TTC on tie lines. The IESO has Operating Agreements with all neighbouring TOPs and
TSPs (i.e., New York ISO, TransÉnergie, Midwest ISO, ITC, Manitoba Hydro, and Minnesota
Power).
For the purposes of outage co-ordination, the IESO exchanges critical outage information with
NYISO, MISO, and TransÉnergie.
2.1.6
Counterflows and Expected Interchange
A portion of scheduled flows to Michigan appear on the New York ties and vice versa. The TTC is
published without taking this coupling into account.
The TTC for each of the paths (with flows in both directions) is the capability of the interface based
on voltage, stability, and thermal requirements. The New York / Michigan coupling is factored into
the scheduling limit when the Dispatch Scheduling and Optimization (DSO) tool determines the
amount of coincident flows on both interfaces. Due to the dynamic nature of loop flows, their
4
Public
Issue 3.0 – June 6, 2012
Part 7.12: Available Transfer Capability Implementation Document
2. Total Transfer Capability
corresponding values are only considered in real time operations and do not affect the ATC or TTC
limits that are published. The need to couple the Michigan and New York TTCs will expire when all
Michigan ties have operating phase shifters.
The net interchange schedule is the sum of all imports (positive) and exports (negative). The IESO
limits the net change from hour-to-hour to 700 MW, unless respecting this limit would negatively
impact reliability. Import and export schedules are adjusted accordingly during real time operations to
ensure that this limit is not violated.
2.2
Publishing Total Transfer Capability
The base quantity for each TTC is published in the Ontario Transmission System document. This
value refers to the TTC with all elements in service.
– End of Section –
Issue 3.0 – June 6, 2012
Public
5
3. Available Transfer Capability
IESO_PRO_0728
3. Available Transfer Capability
3.1
Computing Available Transfer Capability
NERC Standard
MOD-029-1a: Rated System Path Methodology, R7, R8
Requirements R7 and R8 of MOD-029-1a necessitate that the ATC should be calculated as follows:
ATC = TTC – ETC – CBM – TRM + Postbacks + counterflows
F
F
F
F
ATC = TTC – ETC – ETC – CBM – TRM + Postbacks + counterflows
NF
F
NF
S
U
NF
F
The IESO does not have provisions for the purchase and sale of firm and non-firm transmission
services. Hence in the context of MOD-029-1a, the IESO does not draw any distinctions between firm
and non-firm ATC.
In Ontario, the values for ETCF, ETCNF ,CBM, PostbacksF, PostbacksNF and counterflowsF are set to
zero. Therefore, in the context of the Ontario market the ATC = TTC – TRM.
The TRM values applied to the interties for the monthly and annual ATC can be found in
“IESO_PRO_0729 Market Manual 7.11: Transmission Reliability Margin Implementation
Document”. There is no process to allocate transfer or flowgate capability among multiple lines as the
IESO is the only Transmission Service Provider for Ontario.
3.2
Publishing Available Transfer Capability
The IESO uses its DSO tool to produce its advisory dispatches for the day-ahead period (first
published at 11:00 for the following day) up to one hour in advance of real-time. The pre-dispatch
scheduling limits used for the DSO are posted as the short-term ATC. This report can be accessed at:
http://reports.ieso.ca/public/PredispIntertieSchedLimits/PUB_PredispIntertieSchedLimits.xml
The short-term ATC is published in the System Status Report (SSR), the Daily System Adequacy
Assessments (SAA) and the Weekly SAA report. The SSR covers days 0-2 while the Daily SAA
Report details days 3-14. They are published once a day or at any time when there is a material
change to the system.
The monthly and annual ATCs are published as part of the Transmission Rights auction process; the
monthly ATCs in the next two months are covered through the Short Term Auction, and the annual
ATCs for the whole year are covered in the Long Term Auction.
– End of Section –
6
Public
Issue 3.0 – June 6, 2012
Part 7.12: Available Transfer Capability Implementation Document
4. Background Information
4. Background Information
4.1
Transmission Service in Ontario
Ontario’s market design does not allow for the purchase and/or sale of any firm or non-firm
transmission services. There is no system of advance reservations, physical rights and point to point
service. In order for an import/export to be scheduled, it must compete on economics with internal
generation that is dispatched in an economic security constrained manner. If a transaction is
successfully scheduled, the IESO will provide that market participant with access to the transmission
system provided that there is availability on the transmission path to accommodate the transfer.
The Ontario market does not have provisions for point to point service. However the market
framework in Ontario allows fair, open and non-discriminatory access to Transmission service subject
to the imports/exports being competitive in the energy market.
4.2
ATCID NERC Definitions
Table 4-1: ATCID NERC Definitions
Term
NERC Definition
ATC
“A measure of the transfer capability remaining in the physical transmission network for
further commercial activity over and above already committed uses.”
Equation: ATC = TTC - TRM - CBM - ETC
CBM
“The amount of firm transmission transfer capability preserved by the transmission
provider for Load-Serving Entities (LSEs), whose loads are located on that Transmission
Service Provider’s system, to enable access by the LSEs to generation from
interconnected systems to meet generation reliability requirements.”
TRM
“The amount of transmission transfer capability necessary to provide reasonable
assurance that the interconnected transmission network will be secure. TRM accounts for
the inherent uncertainty in system conditions and the need for operating flexibility to
ensure reliable system operation as system conditions change.”
When calculating a TRM value, the following factors should be considered to account for
uncertainties in system conditions:
• Aggregate load forecast error
• Load distribution error
• Variations in facility loading
• Uncertainties in system topology
• Simultaneous transfers and parallel path flow
• Variations in generation dispatch
• Calculation inaccuracies
• Short-term operator response factor
• Short-term vs. long-term timeframes
Issue 3.0 – June 6, 2012
Public
7
4. Background Information
Term
TTC
IESO_PRO_0728
NERC Definition
“The amount of electric power that can be moved or transferred reliably from one area to
another area of the interconnected transmission systems by way of all transmission lines
(or paths) between those areas under specified system conditions. ”
– End of Section –
8
Public
Issue 3.0 – June 6, 2012
Part 7.12: Available Transfer Capability Implementation Document
References
References
Document Name
Ontario Transmission System
Document ID
IESO_REP_0265v20.0
http://www.ieso.ca/imoweb/pubs/marketReports/OntTxSystem
_2011nov.pdf
Daily System Advisory/Summary Report (SSR)
http://reports.ieso.ca/public/SSR/PUB_SSR.htm
Weekly Security and Adequacy Assessment Report (SAA)
http://reports.ieso.ca/public/SAAWeekly/PUB_SAAWeekly.ht
m
Market Manual 7: System Operations Part 7.4: IESO Controlled IMP_POL_0002
Grid Operating Policies
http://ieso.ca/imoweb/pubs/systemOps/so_GridOpPolicies.pdf
Market Manual 7: System Operations Part 7.2: Near-Term
Assessments and Reports
IMP_PRO_0033
http://www.ieso.ca/imoweb/pubs/systemOps/so_NearTermAsse
ssReport.pdf
NERC Standard MOD-001-1a: Available Transmission System
Capability
http://www.nerc.com/files/MOD-001-1a.pdf
NERC Standard MOD-029-1a: Rated System Path
Methodology
http://www.nerc.com/files/MOD-029-1a.pdf
NERC Glossary of Terms
http://www.nerc.com/files/Glossary_of_Terms.pdf
Short Term Transmission Right Auction
http://reports.ieso.ca/public/TRAPreauctionMCPST/
Long Term Transmission Right Auction
http://reports.ieso.ca/public/TRAPreauctionMCPLT/
– End of Document –
Issue 3.0 – June 6, 2012
References–1