Alberta-WECC Intertie Restoration and System Planning Initiative May 7, 2013

Alberta-WECC Intertie Restoration and System
Planning Initiative
May 7, 2013
Kevin Dawson, Senior Program Manager Interties
John Kehler, Director - System Performance
Ebrahim Rahimi, Technical Specialist
Agenda
1. Introductions and schedule
2. Purpose
3. Overview of current intertie limits and drivers
4. High level “Roadmap” of studies
5. Review results to date of intertie SOL study and next
steps
6. High level details of intertie operational studies
7. Discussion of next steps to mitigate simultaneous MATL /
BC limit
2
Purpose of Today’s Session
• Provide context to the AESO’s Intertie Restoration activities
(Section 16 of Transmission Regulation) and System
Planning for intertie transactions (Section 15 of T-Reg)
• Increase industry understanding of what drives intertie limits
and how operating limits may be increased
• Inform participants of study results to date for the intertie SOL
study introduced in July 2012 Intertie Restoration Next Steps
paper
• Provide next steps and timeline for additional activities
3
Current Path Ratings (WECC path rating Catalogue)
• AB – BC (Path 1)
– 1,200 MW import path rating from BC to AB
– 1,000 MW export path rating from AB to BC
• AB – SK (Path 2)
– ±150 MW
• AB – MT (MATL or Path 83)
– 325 MW export path rating from AB to MT (measured at 120s sub)
– 300 MW import path rating from MT to AB (measured at 120s sub)
4
Principles Which Determine Intertie Transfer
Capability
• TTC <= Path Rating
• Operate in preparation for credible contingencies
• Don’t overload equipment upon credible contingencies
• All applicable Alberta and WECC criteria for equipment loading
and system voltages under normal and credible contingency
conditions are followed
• Dynamic stability maintained under internal, external and
intertie trip contingencies (AB can become islanded)
• Imports:
No firm load trip due to UFLS action following the intertie trip; No intertie
trip following outage of largest AB generating unit
• Exports:
Intertie trip should not cause frequency to reach 61Hz; WECC
contingencies should not cause criteria violation in Alberta such as overload and intertie
trip
5
More on Dynamic Stability: System
Response Following Intertie Trip
Immediately following the intertie trip under import conditions:
• The system will naturally respond due to some inherent characteristics
•
•
The regulating reserve units (AGC) respond to frequency drop and increase their output
•
The total effective Alberta load will go down due to voltage and frequency drop
•
The output of some generators will temporarily increase due to governor response
Response of specifically procured services may be required
•
Armed LSSi load will be tripped if frequency drops near to or below 59.5 Hz
Over a longer period, other responses will be triggered:
•
Spinning reserve generators will be dispatched up - starts to have an
impact once directives issued
• The non-spinning contingency reserve generation will be dispatched (will
respond once directives issued)
• The system controller will dispatch up the EMMO
6
Illustrative Example of Principles for 1201L
No temp
Overload
capability
Basic Rules
Portion of
MSSC flow on
intertie
Further
reductions
for stability or
other facility
overloads
TTC Max
-1200/+1000
MW
Facility Rating
Path Rating
Langdon Tx
1)
TTC cannot exceed a Path
Rating
2)
Under credible contingencies, the
intertie facility rating(s) cannot be
exceeded
3)
TTC may be further reduced for;
1200 MVA
-780/+800 MW
4)
1)
stability reasons
2)
Where a path contingency
causes other facility
rating(s) to be exceeded
Limits are set by the most
constraining factor
BC 500 Kv (1201 Line)
7
Current (Pre-MATL) Operational Limits
(TTC) of Path 1
• As per AESO OPP 304 (carried to ATC ID)
– 780 MW import from BC to AB
– 800 MW export from AB to BC
• As per BC Hydro 7T-17 operating order
– 850 MW export from BC to AB
• 1160 MW (short term emergency rating) should risk be accepted by AB
– 800 MW import from AB to BC
• Due to AB based limitations
8
MATL Operational Limits (TTC)
• As per ATC ID
– 310 MW import from MT to AB (measured at AB/MT border)
– 315 MW export from AB to MT (measured at AB/MT border)
• MATL is taken out of service if BC Intertie (1201 Line) is out
of service or direct transfer trip RAS between BC and MATL
is out of service
• MATL also has several WECC related RAS which must be in
service for transfers
• MATL imports also depend on internal AB thermal overload
RAS
9
Simultaneous Operating Limits
Operating Limits
TTCs
Combined AB-BC+MATL+AB-SK flow gate
Simultaneous Transfer Limit on the Alberta/BC,
Alberta/SK and MATL ties (AIC)
Combined AB-BC+MATL+AB-SK
Combined AB-BC+MATL flow gate
AB-BC – Alberta BC
MATL – Alberta Montana
AB-SK – Alberta Saskatchewan
Individual intertie TTC
AB-BC
Combined AB-BC + MATL
Path 83
Simultaneous Transfer Limit on the Alberta/BC
and MATL ties
AB-SK
Path 2
MATL
10
High Level “Roadmap” - Where are we?
3) Operating Study Horizon – Current grid and
range of conditions. Update BC and max
schedule studies given addition of MATL and
updated system conditions.
Now
1) Current
State – BC
existing
operational
studies. Also
determine
max schedule.
2013/2014
2) MATL Energizes – MATL
operational studies recently
completed. BC and max
schedule use existing studies.
2014, 17, 22
4) Planning Study
Horizon – Future
expected grid and
range of conditions.
SOL study in July
‘12 paper.
11
Planning vs. Operating Horizon Studies
Planning Horizon Studies – best case, most optimistic
transmission system state – expected scenarios for
generation/load
Operating Horizon Studies – variety of potential
transmission, generation, load conditions
Operating horizon study based limits are often lower than
planning horizon under all but ideal conditions – produce
tables you see in ID
Planning Study
(Best case
expected
scenarios)
Operations Study
(Wider range of
potential
conditions)
Implementation
(Tools, Training)
12
Planning Horizon Intertie SOL Study - Main
Objectives
• As detailed in July 2012 paper, objective of study
was to look at intertie capabilities on the planning
horizon level
• Determine the capability of the existing/planned
system
• Identify potential mitigation measures that could be
used to restore the capability
13
Planning Horizon Study Scope
Study Years
• 2014 – no FATD Development or Chapel Rock substation,
MATL in service
• 2017 – FATD East and SATR (incl. Chapel Rock) in service
• 2022 – full FATD, higher load, export during peak
Study Stages
Stage 1
Steady state,
focus on AB
(Complete)
Stage 2
Intertie trip
dynamic analysis
(Complete)
Stage 3
Joint studies with
BC Hydro
(Ongoing)
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Key Planning Assumptions: South Alberta
att e
e
System by 2017
o
C ee
Gaet
e s
Jo
so
a s a
a e
Co de
ed ee
e a to
et s o
e
a t at
e u a
a e ood
Anderson
East
Crossfield
Beddington
Sheerness
Coyote
Lake
Crossings
Sarcee
Janet
East
Calgary
Lanfine
Ware
Junction
Oakland
Langdon
Cypress
Shepard
SS-65
Jenner
Bennett
Cassils
Milo
Amoco
Empress
West
Brooks
McNeil
Foothills
Newell
SC1
To British
Columbia
Fidler
Chapel
Rock
Picture
Butte
“MATL”
Bowmanton
Elkwater
Peigan
Journault
Goose
Lake
North
Windy Lethbridge
Flats
Whitla
Wild Rose 1
To
Montana
Notes:
1. This drawing is intended to illustrate the electrical
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Key Planning Assumptions: Load and
Interties
Summer Light Load
Summer Peak Load
Winter Peak Load
2014
2017
2022
8,085 MW
9,081
MW
10,186 MW
N/A 1
12,294 MW
13,433 MW
AB-BC
AB-MT
AB-SK
1,000 MW Export
325 MW Export
150 MW Export
1,200 MW Import
300 MW Import
150 MW Import
13,595 MW
15,213 MW
1: Export at peak load in Alberta is not anticipated in near future
• High export scenarios are under light load and high wind conditions
• High import scenarios are under peak load and low wind conditions
• In 2022, one scenario was tested with maximum export at peak load
assuming substantial wind development may allow export under peak load
conditions
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Key Planning Assumptions: Generation
2014
2017
2022
AB-BC
AB-MT
AB-SK
1,000 MW
export
325 MW
export
150 MW export
1,200 MW
import
300 MW
import
150 MW import
Wind Generation
Summer Light
Load
1,200
MW
Summer Peak
Load
Winter Peak Load
1,700
MW
2,500
MW
N/A 1
0 MW
2,500
MW
0 MW
0 MW
1: Export at peak load in Alberta is not anticipated in near future
• All generators are available (no units on forced or planned outage)
• Cogeneration in the northeast at 75% to 82% capacity depending on the area
• Hydro output at historical seasonal median level
• Other generators are dispatched based on the forecast merit order
• Forecast merit order was used to adjust import and export to find the limits
17
Planning Study Indications to Date (AB side
only)
Caveat: Results are applicable only for the scenarios used in the
planning study. Capabilities under a wider range of operating
conditions will be determined by operating horizon studies.
2014
– Total system import capability could be as high as 900 MW
– Higher load levels and refined understanding of LSSi preserve frequency on
intertie separation
– MATL in service may provide diversity of flow for internal AB gen contingencies
thereby increasing BC TTC and total import capability
– Total system export capability could be as high as 1,000 MW
– If AIL is > 8,000 MW and sufficient frequency regulation (i.e. governor response)
is available
– RAS Considerations – Increase duration of time available for higher transfers
– Langdon to Janet lines
18
Planning Study Indications to Date (AB side
only) – Cont’d
2017 and 2022
– FATD East and Chapel Rock connection facilitates the operation of Path 1 and
MATL at their nominal ratings – but not simultaneously
– 1,200 MW total system import to Alberta is achievable under following
conditions:
– Chapel Rock is in service - no facility overload with trip of largest AB generator
(BC Intertie can transfer up to 1,200 MW and withstand AB contingency)
– Alberta load sufficiently high
– Sufficient frequency regulation
– Current level of LSSi
These maintain AB
frequency stability
Conclusion:
Current studies indicate that the BC-AB Intertie is restored by this period in that it
will be capable of transferring at the current path rating under certain system
conditions and given current planned infrastructure adds. Without additional
mitigation, simultaneous interaction between BC-AB intertie and MATL combined
with frequency stability limits total transfers.
19
Planning Horizon - Next Steps
• Complete joint study with BC hydro to identify any
potential restrictions caused by the BC system
• Currently at preliminary stage
• Targeted for completion by Q3 2013
• This will provide information as to what mitigation
measures may be most beneficial in pursuing
• The outcome of this study will be the starting point for
the WECC path rating studies for Path 1 due to
addition of Chapel Rock
• Initiate WECC path rating process for Chapel Rock
20
Planning Horizon Indication - Total WECC
Potential Import Capability
Indicative Total Alberta Import Capability
AB - Current Plan
AB - w Mitigation
1800
Potential
Mitigation
Import Capability (MW)
1600
1400
Current BC limit (SOO 7T-17)
Updated
Ops Studies
1200
1000
800
600
MATL
Chapel Rock
21
Operating Horizon Study for
Post-MATL, Pre-Chapel Rock Conditions
•
Indications of increased capability in 2014 from planning study must be expanded
on for a range of potential operating conditions
•
Study results must then be implemented via any necessary systems changes and
training
•
Updating the studies is a 2013 priority for the AESO. Completing and
implementation could extend into 2014. The following work is involved:
•
BC Operational Studies
• Consider system conditions and new network topology from MATL in service to Chapel in service
• Update tables for normal conditions and outage conditions
• Review/modify existing RAS / RAS Settings and establish need for any new RAS to support imports/exports.
Possible engagement with WECC RAS committee.
• Engage BC Hydro, North West Energy, and Enbridge
•
Load Shed Service for import (LSSi)
• Assessment on the volumes and thresholds for LSSi for operation up to maximum potential import TTC with the
BC and MATL interties
•
ULFS Policy
• Review policy and strategy of the AIES UFLS program at the targeted higher transfers
22
Possible Mitigation Measures to Maximize
Total Intertie Capability
Simultaneous transfers up to path ratings on BC-AB Intertie and MATL are
not possible without additional mitigation measures over and above the
current level of LSSi.
Potential additional mitigation measures include:
• Isolate MATL connection through a back-to-back HVDC converter
• Isolate 138 kV portion of Path 1 through a back-to-back HVDC converter
• Increase levels of load/generation shedding
• Increased frequency response (AGC, contingency reserve)
• Utilize the existing and/or new interconnection to Saskatchewan
• Energy storage devices/strategies
Based on indications from the joint study with BC Hydro, the AESO will
determine which has best combination of effectiveness and cost efficiency
and then will pursue appropriate avenue (NID or RFP)
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Thank You!
Q&A
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