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Richard Kowalski TECHNICAL DIRECTOR, SYSTEM PLANNING PAC Meeting Review of Transmission Planning Assumptions and Methods APRIL 28, 2015 | MILFORD, MA

Review of Transmission Planning Assumptions and Methods · Review of Transmission Planning Assumptions and Methods ... • Review of Transmission Planning Assumptions and ... •

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Page 1: Review of Transmission Planning Assumptions and Methods · Review of Transmission Planning Assumptions and Methods ... • Review of Transmission Planning Assumptions and ... •

Richard Kowalski T E C H N I C A L D I R E C T O R , S Y S T E M P L A N N I N G

PAC Meeting

Review of Transmission Planning Assumptions and Methods

A P R I L 2 8 , 2 0 1 5 | M I L F O R D , M A

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Outline

• Background

• Review of Transmission Planning Assumptions and Methods – Approach

• Resource Unavailability/Uncertainty

• Assessment Methods and Considerations

• Data Requirements and Review

• Next Steps

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BACKGROUND

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Discussed on September 19, 2014

• Transmission Planning Considerations

• Resource Unavailability

• Probability of Critical System Conditions

• Review of Transmission Planning Methods and Assumptions - Approach

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Purpose/Objective

• Review the key assumptions used in transmission planning and how they should be applied

• Consider different analysis methodologies which may better quantify the likelihoods of transmission planning-related risks

• NESCOE to ISO/PAC, 4/19/13 ‘Problem statement: The use of subjective terms in our current planning

procedure allows a wide range of subjectivity in base case development that can effectively defeat the purpose of standards. In New England, development of transmission planning base cases with widely varying degrees of likelihood calls into question what context can be given to terms such as “reasonable stress.” ‘

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Recent Changes to Planning Assumptions

• ISO has been making changes to planning assumptions in response to stakeholder recommendations

• Energy Efficiency is now forecast for the period following the most current Forward Capacity Auction – provides 10 years of forecast data

• PV forecasting method has been developed

• ISO no longer maintaining external export transfers in Needs Assessments

• ISO no longer keeps fast start resources out of service in base cases; modeling 20% out of service

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REVIEW OF TRANSMISSION PLANNING ASSUMPTIONS AND METHODS - APPROACH

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Items to be Considered in this Effort

• Resource Uncertainty/Unavailability

• Assessment Methods and Considerations

• Data Requirements

• Load Interruption

• System Performance Criteria

• Transmission Uncertainty/Unavailability

• Planning a Maintainable System

• Planning Approaches to Consider Longer Term Uncertainties

• Longer Term Economic Study Methods

• Other?

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RESOURCE UNAVAILABILITY/UNCERTAINTY

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Resource Unavailability Modeled in Consideration of Many Different Situations. Examples:

• Long duration unplanned outage (eg. Stator, GSU failure, fire)

• Short duration unplanned outage (eg. Tube leak, high wind)

• Sudden outage (eg any turbine trip, intermittent fault)

• Common mode outage – Sudden – Long duration

• Failure to start when called on

• Failure to be at the required output when needed (eg units that start, but sit at min and miss the whole peak)

• Failure to stay running after started

• Fuel supply unavailability

• Common mode fuel supply failure

• Avoidance of RMRs

• Failure to meet contractual service obligations

• Unanticipated temporary shutdown (eg unit stops operating for business reasons)

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• 0 MW audited SCC (3 years of 0’s to be automatically retired – Bridgeport Harbor 2)

• Unit physically unable to operate (eg Millstone 1)

• Announced Retirement

• Unannounced Retirement

• Static Delist

• Limited Energy units (eg emissions restrictions)

• Regulatory shutdown (eg NE nukes 1996-1998)

• Scheduled Maintenance

• Maintenance overrun

• Derate due to ambient air/water conditions – Including full shut down – Difference between output at 90 degrees and 100

degrees

• Intermittency – Seasonal – Daily – Hourly

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General Representation of Resource Unavailability in Studies

• Contingency modeling to represent sudden events – Normal/design contingencies – Extreme contingencies

• Base condition modeling to represent longer duration, cumulative or concurrent events – Reasonably anticipated events – Extreme System Conditions

• Scenario analysis can be used to examine broad trends and possibilities – Model each scenario as a fundamental assumed base condition

• Significantly compounds the testing and analysis effort – When to take action based on a scenario?

• There is not likely one study or one approach which captures all of these

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Resource Contingency Modeling to Represent Sudden Events - Normal/Design Contingencies

• Related problems must be addressed

• Representative situations: – Sudden outage (e.g.; any turbine trip, intermittent fault) – Sudden common mode outage (e.g.; Mystic 8&9) – Failure to start when called on – Failure to reach desired MW when needed – Failure to stay running after started – Sudden outage precipitated by a failure which then results in a

long-term outage

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Resource Contingency Modeling to Represent Sudden Events - Extreme Contingencies

• Evaluate mitigating measures for related problems

• Representative situations: – Sudden outage of all generating units at a generating station – Loss of one generator followed by loss of another generator,

without system adjustments between outages (N-2) – Loss of two generating stations

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Modeling of Reasonably Anticipated Conditions in Base Cases

• Related problems must be addressed

• Representative situations: – Short-mid duration unplanned outage (e.g.; tube leak) – Long duration planned (unplanned?) outage – Range of anticipated seasonal performance – 0 MW audited SCC – Unit physically unable to operate (e.g.; Millstone 1) – Announced retirement – Scheduled maintenance – Maintenance overrun – Derate/full shut-down due to ambient air/water conditions – Static delist request – Limited energy units (e.g.; emissions restrictions) – RMR avoidance (?)

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Modeling of Unusual/Uncommon Conditions in Base Cases - Extreme System Conditions

• Evaluate mitigating measures for related problems

• Proposed representative situations: – Common mode fuel supply failure – Fuel supply unavailability

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Scenario Analysis – Modeling of Possible Future Conditions in Base Cases

• Consider which problems should be mitigated/addressed based on cost, risk, etc. – Region needs to develop criteria and guidelines regarding thresholds

of acceptability

• Representative situations: – Long(est) duration unplanned outage (e.g.; generator stator, GSU

failure) – RMR avoidance (?) – Common mode outages – Unanticipated temporary shutdown (e.g.; financial shutdown) – Unannounced, relative to planning horizon, retirement (e.g.; Salem

Harbor)

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ASSESSMENT METHODS AND CONSIDERATIONS

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Objective of Reliability Analyses

• Deterministic Transmission Planning and Probabilistic Resource Adequacy Assessment are complementary processes which, together, assess system reliability

• Resource Adequacy employs probabilistic analysis to determine the amount of resource required (some locational inference)

• Transmission Planning employs deterministic analysis to determine if the transmission system can securely deliver resource to load during reasonable credible discrete events and load levels

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Probabilistic Resource Adequacy Assessment - Characteristics

• Reflects the statistics of historical resource performance

• Considers the load forecast probability distribution

• Transmission capabilities based on N-1 (&N-1-1) events represented by static transportation/transfer limits – Some limited ability to represent nomograms

• Global/sub-area probabilistic metric (e.g.; LOLE, LOLP, EUE)

• Presumes the transmission system meets (deterministic) criteria

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Probabilistic Resource Adequacy Assessment - Pros/Cons

• Reflects a comprehensive range of resource and peak load conditions

• Singular quantified metric of reliability – May/may not provide insight regarding risk

• Captures a limited number of transmission constraints

• Overlapping/intersecting transmission constraints cannot be modeled accurately

• Does not reflect the influence of generation dispatch and load level on transfer limits (simultaneous/multi-dimensional transfer limits)

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Deterministic Transmission Planning - Characteristics • Discrete modeling of reasonably stressed conditions

• Different types of resource unavailability modeled as discrete events

• Specific/limited discrete load levels modeled (e.g.: 90/10, shoulder, light)

• Significant power transfers (semi-static) modeled – Can result from generation unavailability assumptions – Can be specifically modeled to reflect system transfer objectives (reliability,

economics, policy) and obligations

• Detailed representation of transmission network

• All sudden transmission and generation outage contingencies explicitly tested – Single element, multi-element, Extreme Contingencies

• Element/location -based pass/fail metrics – e.g.: overloads, unacceptable voltages, instability, etc. – Per NERC TPL-001-4, some types of load interruption allowed for different

contingencies

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Deterministic Transmission Planning - Pros/Cons

• Models a limited number of discrete significant resource and load conditions to capture the exposure to a wide range of system conditions – Too severe? – Insufficient? – “Have the right resource/load conditions been tested?”

• All transmission constraints and conditional dependencies can be captured

• Usually requires an extensive amount of testing and post-processing analysis to capture all critical conditions and events

• Can capture, but blur, the distinction among different types of resource unavailability

• Requires consideration of the impact of specific resource operating characteristics

• Can identify all constraints; – Pass/Fail – One failure is too many – No quantification/metric of global reliability

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Composite Reliability Assessment - Characteristics (available approaches?)

• Examples: EPRI-TRANSCARE; EPRI-PWR(CREAM)

• Reflects the statistics of historical resource performance

• Considers the load forecast probability distribution

• Detailed representation of transmission network

• Reflects the statistics of historical transmission and generation outage contingencies – Single element, multi-element, Extreme Contingencies – Tested probabilistically (Monte Carlo)

• Global/sub-area probabilistic metric (e.g.; LOLE, LOLP, EUE)

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Composite Reliability Assessment - Pros/Cons (available approaches?) • Reflects a comprehensive range of resource and peak load conditions

• May consider a broad depth of contingencies (N-1, N-X)

• Fails to meet the objective of reliability analyses * – Only captures a limited number of transmission constraints – Does not assure that system will be designed to withstand all relevant transmission contingencies;

does not meet NERC and NPCC criteria – Does not assure that the system will be planned such that it can be operated securely – Doesn’t distinguish between sudden resource outages (contingencies) and longer term resource

outages (base conditions)

• Doesn’t recognize system adjustments between preparing for all N-1-1 events after a specific N-1 event

• Resource outage statistics may not capture the significance of different types of resource unavailability

• Resource capacity value may not reflect the typical operating range of some resources (e.g.; hydro resources)

• Probabilistic metric may/may not be meaningful/comparable

• May or may not require an extensive amount of testing and post-processing analysis

• Current approaches may have use for comparison of transmission solution alternatives already proven to meet all reliability requirements

* BC Hydro approach may be an exception 24

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Characteristics of a Comprehensive Approach

• Reflects the statistics of historical resource performance

• Recognizes the impact of specific resource operating characteristics

• Respects the distinction among different types of resource unavailability

• Considers the load forecast probability distribution

• Detailed representation of transmission network

• All relevant sudden transmission and generation outage contingencies must be explicitly tested (N-1, N-1-1, EC) – Single element, multi-element, Extreme Contingencies

• Might be useful to consider less-likely multiple contingencies (N-3+) based on historical statistics

• Recognizes acceptable risk based on type of contingency

• Element/location –based metrics

• Global/sub-area probabilistic metric (e.g.; LOLE, LOLP, EUE)

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Review of Available Probabilistic-based Transmission Assessments • What studies have been done or are in progress?

• What were the study objectives?

• How were the studies performed? – Tools – Methodologies – Data

• What were the results/conclusions/observations?

• What approaches might be useful in New England – Tools and methodologies – Nature of applicability – Recommendations on study approach

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Examination of Tools Available for Incorporating Probabilistic Considerations for Transmission Assessment

• Any comprehensive transmission assessment method employing probabilistic considerations must treat N-1 and N-1-1 transmission contingencies deterministically; may be useful to treat N-3+ transmission contingencies probabilistically

• What’s commercially available?

• What enhancements are recommended?

• What can be applied today? In what manner?

• Can commercial tools be customized? – What are the specifications?

• Can/should tools be developed internally?

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DATA REQUIREMENTS AND REVIEW

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Data Requirements

• Any probabilistic method for transmission assessment will require an extensive amount of data – Transmission topology & contingencies – Resource sudden contingencies – Data that describes the appropriate resource unavailability – Load data

• Different tools/approaches may require different forms/detail of data

• Specific resources and load details can have a significant impact on some transmission constraints

• Need relevant availability metrics for different types of resources: – Thermal generation (base load/cycling) – Fast start generation (peaking) – Hydro: Pondage & Run-of River – Pumped Storage Hydro – Wind – PV – EE/Demand Resources/Distributed Resources

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Data Concerns

• Transmission system data and contingencies are known

• Transmission outage statistics not currently relevant for N-1 or N-1-1 events, due to NERC and NPCC requirements

• Transmission outage statistics not readily available for Extreme Contingencies

• Typical resource outage statistics may not capture the significance of different types of resource unavailability

• Resource capacity value may not reflect the typical operating range of some resources (e.g.; hydro resources)

• Historical resource data – Intermittent resources

• Wind • Seasonal hydro

– GADS/Eford

• Is Eford always statistically valid, particularly where specific impact matters?

• Resource Mean or Expected Values may be misleading

• Forecast load distribution is available – Focus has been on peak – Is the load shape accurate?

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Data Review and Development

• Review the sources of historical data for different resources

• How has data been processed?

• How has Eford been calculated?

• When is Eford acceptable/questionable for transmission planning purposes?

• What are alternative/corroborative sources of data?

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NEXT STEPS

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Next Steps

• Review available studies

• Review available tools and methodologies

• Review where and how resource availability information is developed; consider refinements particular to transmission assessment

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