Massive Transient Stability Based Cascading Analysis and On-line Identification of Critical Cascades

Transcription

1 1 Massive Transient Stability Based Cascading Analysis and On-line Identification of Critical Cascades Paper Number: 16PESGM2419 Marianna Vaiman, V&R Energy 2016 IEEE PES General Meeting, Boston, MA CFWG Panel Session Cascading Outages - Dynamics, Protection, Validation and Data July 20, 2016

2 2 Contents: 1. Massive Transient Stability Based Cascading Analysis 2. On-Line Identification of Critical Cascades

3 3 1. Massive Transient Stability Based Cascading Analysis

4 CWFG Survey What would make you more satisfied/are there any computations associated with cascading outages you feel present tools fail to address? Dynamic simulation of cascading outages which should include protection system modeling Better solution algorithms/robust tools Automated/optimized mitigation measures Identifying and classifying widespread system area limitation versus local area limitation Identifying and quantifying the risk of complicated cascades and large blackouts in a way that allows these risks to be monitored and mitigated Having a screening tool Wide area visualization and analysis tools that can identify stress indicators early and help operators take appropriate actions

5 NERC Standards Related to Cascading PRC Disturbance Monitoring and Reporting Requirements TPL Transmission System Planning Performance Requirements CIP Physical Security CIP Cyber Security BES Cyber System Categorization PRC Transmission Relay Loadability PRC Generator Frequency and Voltage Protective Relay Settings EOP Capacity and Energy Emergencies EOP Load Shedding Plans TOP Transmission Operations TOP Transmission Operations FAC Transmission Vegetation Management FAC System Operating Limits Methodology for the Operations Horizon IRO Reliability Coordinator Operational Analyses and Real-time Assessments IRO-010-1a Reliability Coordinator Data Specification and Collection

6 6 An Approach to Transient Stability Based Cascading Analysis Implemented in Potential Cascading Modes Transient Stability (PCM-TS) application: Analyzes cascading outages from transient stability perspective while considering protection system Used to address NERC TPL standard Addresses the following aspects of assessment of cascading outages: Initiating events three-phase & unbalanced faults, and user-defined switching sequences Considers generator out-of-step conditions, overloads, transient voltage deviation Incorporates protection system modeling

7 7 A Cascading Event from Transient Stability Perspective An event is classified as a cascading outage if at least one of the conditions is met: Sharp drop in transient voltages in a large part of the network Sharp drop in frequency followed by system separation Islands are formed as a result of protection operation, with significant amount of load/ generation within the island Disconnection of large amount of generation Disconnection of large amount of load

8 8 Time-Domain Simulation during Cascading Analysis Each cascading event is simulated using time domain simulation: Associated time constants are specified as the user input During a cascading event, elements are being tripped. Tripped elements may be lines, transformers, loads, and generators

9 9 Critical Cascade Criteria Time-domain simulation runs until at least one of the Critical Cascade criteria is met: Islanding Total MW of load in all created islands, except the largest island exceeds a pre-defined threshold Interface limit violation Interface MW flow during cascade exceeds interface limit MW load loss Total MW loss of load tripped during cascade exceeds a pre-defined threshold MW generation loss Total MW loss of generation exceeds a pre-defined threshold Cascade propagation Cascade propagates beyond the user-defined control area(s)

10 10 Generator Angle Deviation Checks the maximum change in the rotor angle deviation Computes the difference between maximum and minimum generator rotor angles, and determines the maximum difference: Computed during user-defined time interval Units with smaller real power output may be excluded from monitoring Done for informational purposes only; this is not included in Critical Cascade criteria

11 11 Checking Steady-State Stability After time-domain computation is completed, all elements tripped as a result of a cascading chain, are tripped using steady-state (e.g., load flow) computation Power flow solution is obtained

12 12 Critical Tripping Criteria and Delays Tripping occurs during a cascading event if at least one of the tripping criteria is met: Line tripping threshold Transformer tripping threshold Load tripping threshold Generator tripping thresholds Element Tripping and Delays: Tripping occurs only if a criterion continues to be met during Relay Delay time interval In this case, the element will be tripped after Relay Delay time interval elapsed

13 13 Modeling Relay Operation Four types of relays considered during the analysis: Distance relays Overcurrent relays Undervoltage relays Underfequencyrelay It is assumed that the above relays are installed on all lines, transformers, loads, and generators Relay operation is modeled using the user-defined delays

14 14 Types of Cascading Outcomes Based on determination and comparison of damping parameters Outcome Outcome Type 1 Decreasing amplitude oscillations 2 Increasing amplitude oscillations 3 Oscillations with decreasing frequency 4 Oscillations with increasing frequency 5 Monotonously increasing frequency 6 Monotonously decreasing frequency

15 15 Results of Massive Cascading Analysis Detailed and summarized results of cascading analysis are produced

16 16 2. On-Line Identification of Critical Cascades

17 17 On-Line Cascading Analysis Steady-state analysis of fast developing cascading events when Operator has no time to react Uses node-breaker model of the system: SCADA-based State-Estimator cases or PMU-based Linear State Estimator Cases Initiating Events are complex contingencies (N-2, stuck breaker) beyond N-1 which are addressed in regular dispatch Classifies every Initiating Event as Critical, Near critical or Acceptable: Based on operational reliability criteria applied to consequences of potential cascade Implemented in ROSE/PCM tool

18 18 Identification of a Critical Cascade Purpose: classification of Cascade as Critical is the identification of IROL violation based on measurable consequences Existence of a Critical Cascade longer than 30 minutes means IROL violation reportable event Concept of Critical Cascade is a consistent, quantifiable and auditable process of IROL violation analysis Concept of Critical Cascade is a practical instrument to satisfy generic NERC requirements of IROL compliance Source: ISONE and V&R Energy

19 19 Attributes of a Critical Cascade Critical Cascade satisfies at least one of the following criteria: System wide voltage collapse occurs upon applying initiating contingency or as the result of cascading tripping Islanding of the system and total MW of load in separated islands is greater than pre-defined threshold Actual interface MW flow during cascade exceeds stability interface limit by pre-defined % level Total MW loss of load exceeds pre-defined threshold Total MW loss of generation exceeds pre-defined threshold Cascade propagates beyond Balancing Area footprint Each criterion for a Critical Cascade is configurable : Enable/Disable Threshold value

20 20 Data Flow for On-Line Analysis Source: Slava Maslennikov, Eugene Litvinov, ISONE

21 21 Process of On-Line Cascading Analysis Source: Slava Maslennikov, Eugene Litvinov, ISONE

22 22 On-line ROSE-PCM GUI Source: Slava Maslennikov, Eugene Litvinov, ISONE

23 23 Metrics of Locality of Voltage Collapse Non-convergence of power flow is reported as voltage instability. Majority ( >90%) of voltage instability has local impact and affects quite limited MW of loads Typical power flow solution cannot distinguish local from wide spread voltage instability Locality of voltage collapse is measured by the minimal MW of load shedding necessary to prevent voltage collapse Source: Slava Maslennikov, Eugene Litvinov, ISONE

24 Thank you! 24