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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

[email protected]

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

2 IEEE PES GM 2017, Chicago, July 19, 2017

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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IEEE PES GM 2017, Chicago, July 19, 2017

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


TRE Texas Reliability Entity

RFC Reliability First Corporation

WECC Western Electricity


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


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


* - 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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/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.



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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.



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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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Questions

? Milorad Papic

Tel: (208) 388-2343 Email: [email protected]

25 IEEE PES GM 2017, Chicago, July 19, 2017

mailto:[email protected]

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