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Tutorial: Industry Practices, Needs, and
Challenges in Cascading Analysis
NERC standards applicable to analysis of cascading outages
IEEE PES General Meeting, Chicago, July
19, 2017
Milorad Papic Idaho Power
OUTLINE 1. An Overview of Standards
2. Who are NERC & WECC?
3. What is a Cascading Outage?
4. NERC standards applicable to Cascading
5. WECC reliability criteria applicable to Cascading
6. IPC Cascading Methodology
7. Conclusions
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1. An Overview of Standards • ISO (International Organization for Standardization) is the world’s largest
developer of voluntary International Standards.
• NEMA (The National Electrical Manufacturers Association) develops
codes and standards that are generally applied in North America
• IEC (International Electrotechnical Commission) is created to standardize
electrical and electrically related equipment across the world.
• ITU (International Telecommunication Union) is the United Nation
specializes agency for information and communication technologies (ICTs).
• ANSI (American National Standards Institute) coordinates U.S. standards
with international standards to achieve uniform conformance.
• IEEE (Institute of Electrical and Electronics Engineers) develops own
standards (i.e. IEEE Std 859-1987-R2008, IEEE Std 762-2006, etc.)
• NERC (North American Electric Reliability Corporation) develops and
enforces more than 150 Reliability Standards.
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2. NERC Regional Entities
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FRCC Florida Reliability
Coordinating Council
SERC SERC Reliability Corporation
MRO Midwest Reliability
Organization
SPP RE Southwest Power Pool
Regional Entity
NPCC Northeast Power
Coordinating Council
TRE Texas Reliability Entity
RFC Reliability First Corporation
WECC Western Electricity
Coordinating Council
IEEE Boise, Nov 16, 2012
2. WECC Balancing Authorities and Sub-regions
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3. What is a Cascading Outage?
Various Definitions: • NERC definition: The uncontrolled
successive loss of system elements triggered by an incident at any location. Cascading results in widespread electric service interruption that cannot be restrained from sequentially spreading beyond an area predetermined by studies.
• CFWG definition: Cascading Failure is a Sequence of Dependent Failures of Individual Components that successively Weakness the Power System
Dominant Causes Cascading is a complex interdependent event
that result from:
• Equipment failures
• Protection Failures
• Control actions failure
• Tree Contact
• Operator error
• Thermal overloads
• Voltage violations
• Proximity to security limits
• Changes in power flow
• Voltage instability
• Dynamic instability
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3. Generic Scenario of a Cascading Blackout
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1 2 6
3
5 4
0 0 – System State Before
Blackout
1 – Contingency Conditions
2 – Triggering Events
3 – Power Flow Surges, Voltage
problems, Overloads
4 – Protection System Trips
Lines, Transformers, Generators
5 – System Separation, Instability
and Voltage Collapse
6 - Blackout System State
IEEE PES GM 2017, Chicago, July 19, 2017
3. Progression of a Cascading Event The outage of the overloaded components can progress either
slowly (steady-state progression), or quickly (transient progression).
• The transient progression usually involves voltage instability, frequency instability and small signal instability (power oscillations) and its time scale is between seconds and several tens of seconds. The examples are blackouts in US-West on July 2, 1996 and the most recent one in India on August 31, 2012.
• The slow progression involves line tripping between fairly large time intervals, in order of minutes. In this case the line tripping occurs either after exceeding a short-term emergency line loading limit or the line sags and short-circuit between the line and trees takes place. The examples of the slow progressing cascading is the blackout in France on December 19, 1978, initial phase of the NE US blackout on August 14th, 2003 and blackout in Italy on September 28, 2003.
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3. Operation Horizon (SOL & IROL)
System Operating Limit (SOL)
SOLs are based upon certain operating criteria. These include, but are not limited to:
• Facility Ratings (Applicable pre- and post-Contingency equipment or facility ratings)
• Transient Stability Ratings (Applicable pre- and post-Contingency Stability Limits)
• Voltage Stability Ratings (Applicable pre- and post-Contingency Voltage Stability)
• System Voltage Limits (Applicable pre- and post-Contingency Voltage Limits)
Interconnection Reliability Operating Limit (IROL)
A System Operating Limit that, if violated, could lead to instability, uncontrolled separation, or Cascading outages that adversely impact the reliability of the Bulk Electric System.
• Interconnection Reliability Operating Limit Tv
The maximum time that an IROL can be violated before the risk to the interconnection or other Reliability Coordinator Area(s) becomes greater than acceptable.
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4. NERC Reliability Standards • Modeling Standards establish consistent modeling data requirements and
reporting procedures for development of cases necessary to support analysis of the reliability of the interconnected transmission system.
• Planning standards specify technical and design criteria and procedures in the planning and development of transmission systems, such as NERC TPL (Transmission Planning) standards.
• Operations standards specify the operations to protect the reliability and security of power supply and operation under normal and abnormal operating conditions, such as NERC TOP (Transmission Operations) standards, NERC IRO (Interconnection Reliability Operations and Coordination) standards, and NERC VAR (Voltage and Reactive) standards.
• Protection and CIP standards specify the coordination and responsibilities of the protection, such as NERC PRC (Protection and Control) standards, and NERC CIP (Critical Infrastructure Protection) standards.
• Emergency standards specify the procedures, implementing plans, and responsibilities relating to operating emergencies, such as NERC EOP (Emergency Preparedness and Operations) standards.
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4. NERC Standards Applicable to Cascading
Modeling MOD-032-1 MOD-026-1
MOD-033-1 MOD-027-1
MOD-028-02
Planning
TPL-001-4 * (2015-10)
TPL-007-2* (2013-03)
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Emergencies EOP-004-4* (2015-08) EOP-006-3* (2015-08) EOP-006-3* (2015-08) EOP-011-1
Operation TOP-001-4* (2016-01) TOP-002-4 TOP-010-1 IRO-002-5* (2016-01) IRO-008-1 IRO-009-1 IRO-010-1
Protection/CIP PRC-002-2 PRC-023-4 PRC-024-2 CIP-002-5* (2016-02) CIP-014-2
IEEE PES GM 2017, Chicago, July 19, 2017
* - Standards under development
4. Planning Standards TPL-001-4
Title: Transmission System Planning Performance Requirements
Purpose: Establish Transmission system planning performance requirements within the planning horizon to develop a Bulk Electric System (BES) that will operate reliably over a broad spectrum of System conditions and following a wide range of probable Contingencies.
TPL-007-2 Title: Transmission System
Planned Performance for Geomagnetic Disturbance Events
Purpose: Establish requirements for Transmission system planned performance during geomagnetic disturbance (GMD) events within the Near-Term Transmission Planning Horizon.
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4. Planning Std. TPL-001-4 R5. Each TP and PC shall have criteria
for acceptable System steady state
voltage limits, post-Contingency voltage
deviations, and the transient voltage
response for its System. For transient
voltage response, the criteria shall at a
minimum, specify a low voltage level and
a maximum length of time that transient
voltages may remain below that level.
R6. Each Transmission Planner and
Planning Coordinator shall define and
document, within their Planning
Assessment, the criteria or methodology
used in the analysis to identify System
instability for conditions such as
Cascading, voltage instability, or
uncontrolled islanding.
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R3.5 - Identify the planning and
extreme events in Table 1 which are
expected to produce more severe
system impacts, and evaluate their
consequences including
Cascading. Conduct a cascading
evaluation to develop possible
actions to reduce the Cascading
likelihood or “mitigate the
consequences and adverse
impacts”.
R4.5. If the analysis concludes there
is Cascading caused by the
occurrence of extreme events, an
evaluation of possible actions
designed to reduce the likelihood or
mitigate the consequences of the
event(s) shall be conducted.
5. WECC TPL-001-WECC-CRT-3
Purpose To facilitate coordinated near-term and
long-term transmission planning within the Interconnection of the Western Electricity Coordinating Council (WECC), and to facilitate the exchange of the associated planning information for normal and abnormal conditions.
Positive reactive power margin for the following:
– For transfer paths 105% or 102.5% of path flow for P0-P1 or P2-P7 events respectively.
– For load areas 105% or 102.5% of forecasted peak load for P0-P1 or P2-P7 events respectively.
Cascading and Uncontrolled Islanding
- When a post contingency analysis results in steady-state facility loading that is either in excess of a known BES facility trip setting, or exceeds 125% of the highest seasonal facility rating for the BES facility studied.
- When transient stability voltage response occurs at any applicable BES bus outside of the criteria stated in Requirement for Transient performance.
- When either unrestrained successive load loss occurs or unrestrained successive generation loss occurs.
https://www.wecc.biz/_layouts/15/WopiFrame.aspx?sourcedoc=/Reliability
/TPL-001-WECC-CRT-3.docx&action=default&DefaultItemOpen=1
Voltage Stability
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5. TPL-001-CRT-3 Stability Criteria
• All oscillations that do not show positive damping within 30-seconds after the start of the studied event shall be deemed unstable.
• When a post contingency analysis results in steady-state facility loading that is either in excess of a known BES facility trip setting, or exceeds 125% of the highest seasonal facility rating for the BES facility studied. If the trip setting is known to be different than the 125% threshold, the known setting should be used.
• When either unrestrained successive load loss occurs or unrestrained successive generation loss occurs.
• For transfer paths, all P0-P1 events shall demonstrate a positive reactive power margin at a minimum of 105 percent of transfer path flow.
• For transfer paths, all P2-P7 events shall demonstrate a positive reactive power margin at a minimum of 102.5 percent of transfer path flow.
• For load areas, all P0-P1 events shall demonstrate a positive reactive power margin at a minimum of 105 percent of forecasted peak load.
• For load areas, all P2-P7 events shall demonstrate a positive reactive power margin at a minimum of 102.5 percent of forecasted peak load.
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5. WECC TPL-001-WECC-CRT-3
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https://www.wecc.biz/_layouts/15/WopiFrame.aspx?sourcedoc=/Reliability
/TPL-001-WECC-CRT-3.docx&action=default&DefaultItemOpen=1
6. Cascading Compliance Study Process
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Base Case
(N-0) state
TPL-001-4 Planning Events (P1-P7) Extreme Events (E1-E3)
Selecting
Initiating
Events
Applying Cascading
Methodology
Classification of
Initiating Events
Non-Critical
Critical
Identify and Apply
Mitigation Measures
Report
Results
6. Base Case Analysis
Case Development • Studied cases should be developed from data
consistent with what is provided under the MOD-031 and MOD-032 standard
• System Models Represent Existing Facilities
• Known outage(s) of generation or Transmission Facility (ies) with a duration of at least six months.
• New planned Facilities and changes to existing Facilities
• Real and reactive Load forecasts
• Known commitments for Firm Transmission Service and Interchange
• Resources (supply or demand side) required for Load
Normal/Stressed* Conditions • All facilities are modeled to reflect normal
operating conditions and limits
• The loading of Lines and equipment shall be within normal rating limits.
• Voltage levels shall be maintained within plus or minus 5% of nominal voltage
• Electrical demand shall be supplied, and all contracted firm (non-recallable reserved) transfers shall be maintained.
• Stability of the studied system shall be maintained.
• Cascading outages shall not occur.
* Studied cases are stressed to identify potential future transmission system weaknesses and limiting facilities
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6. Initiating N-1 Events
Single P1-P2 Events
• P1 - 3ph fault of a single Generator Unit/Transmission Circuit/ Transformer/ Shunt Device/ Single Pole of DC Line
• P2-1 - Opening of a line section w/o a fault
• P2-2 - SLG fault with normal clearing, Bus Section
• P2-3 - SLG fault with normal clearing, Breaker internal fault (non-Bus-tie Breaker)
• P2-4 - SLG fault with normal clearing, Breaker internal fault (Bus-tie Breaker)
Performance Requirements
• Line and equipment loadings shall be within emergency rating limits.
• Voltage levels shall be maintained within plus 5% or minus 8% of nominal voltage for all busses.
• No loss of customer electric demand
• No curtailment of contracted firm (non-recallable reserved) transfers shall be required.
• Stability (angular and voltage) of the network shall be maintained.
• Cascading outages shall not occur.
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6. Initiating Multiple N-K Events
TPL P3-P7 Events • P3 - loss of generator unit followed by system
adjustments, followed by a P1 event
• P4-1 to P4-4 n- SLG fault w/ delayed clearing (stuck breaker), Generator/Transmission Circuit/ Transformer/Shunt
• P4-5 - SLG fault w/ delayed clearing (stuck breaker), Bus Section
• P4-6 - SLG fault w/ delayed clearing (stuck Bus-tie breaker), Bus Section
• P5-1 to P5-4 - SLG delayed fault clearing of a Generator/Transmission Circuit/ Transformer/ Shunt Device
• P5-5, SLG delayed fault clearing of a Bus Section
• P6-1 to P6-3, loss of Transmission Circuit, Transformer, or Shunt Device followed by system adjustments, followed by a Transmission Circuit/Transformer/Shunt Device
• P7, SLG Line fault with normal clearing, any two adjacent circuits on common structure
Performance Requirements
• Line and equipment loadings shall be within emergency thermal rating limits.
• Voltage levels shall be maintained within plus 5% or minus 10% of nominal voltage for all busses.
• Stability (angular and voltage) of the network shall be maintained.
• Planned outages of customer demand or generation may occur.
• Contracted firm (non-recallable reserved) transfers may be curtailed.
• Cascading outages shall not occur.
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6. Initiating Extreme Events
TPL Extreme Events (EE) 1. Loss of a single generator, Transmission
Circuit, single pole of a DC Line, shunt device, or transformer forced out of service followed by another single generator, Transmission Circuit, single pole of a different DC Line, shunt device, or transformer forced out of service prior to System adjustments.
2. Local area events affecting the Transmission System
3. Wide area events affecting the Transmission System
CIP-014-2 Events • The criteria to identify extreme
contingencies based on CIP-014-2 include:
• Transmission facilities operated at 500 kV or higher;
• Transmission facilities operated between 200 kV and 499 kV with “aggregate weighted value” exceeding 3000 units. Details are given Table below.
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6. IPC Cascading Methodology
• Fast sequential contingency simulation is used to identify potential cascading modes.
• Outages are consecutively applied until:
– System fails to solve due to voltage instability;
– Thermal/voltage violations are alleviated or drop below the thresholds.
• Loss of load and generation is monitored and reported
• Probabilities of initiating events and consequences may be added
• Ref-M. Papic, and O. Ciniglio, “Prediction and Prevention of Cascading Outages in Idaho Power Network”, Proceedings of PES General Meeting 2014, Washington DC
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6. CIP-014-2 Analysis
• Purpose is to identify and
protect Transmission stations
and Transmission substations,
and their associated primary
control centers, that if rendered
inoperable or damaged as a
result of a physical attack
could result in widespread
instability, uncontrolled
separation, or Cascading
within an Interconnection.
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M. Papic, O. Ciniglio, and M. Vaiman, “Practical Experience in Assessing the Effects of
Extreme Contingencies with Respect to Standards TPL-001-4 and CIP 014-1” paper
15PESGM0571, PES GM 2015, Denver, July 2015
7. Conclusions
• A systematic list of NERC standards applicable to cascading in areas of planning and operation of Bulk Electric System (BES) is presented.
• The WECC reliability criteria related to cascading and uncontrolled islanding is presented.
• The cascading methodology implemented by Idaho Power is presented
• A procedure to identify and evaluate the initiating events and perform step by step cascading analysis is presented.
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IEEE PES GM 2017, Chicago, July 19, 2017
Questions
? Milorad Papic
Tel: (208) 388-2343 Email: [email protected]
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