The document discusses predicting the risk of cascading power outages. It presents a simulation-based method to identify potential cascading modes and proposes online risk monitoring of both traditional contingencies and potential cascading modes. Higher power transfers and structural degradation can increase the likelihood of cascades. The method aims to assess consequences of initiating events and categorize cascading risks into tiers to better plan for credible and unacceptable scenarios.

1. Predicting Risk of Cascading Outages Stephen Lee Senior Technical Executive October 2008

2. Cascading Outages Rip Across an Interface – Triggered by Next Random Outage Higher Power Transfer Stretches the Fabric and Makes Cascades More Likely

3. Testing the Strength of a Holely Fabric Pulling at a location of the fabric tests vulnerability to Higher net export or import in a local area

4. Acceptable Consequences of Contingency Categories A, B, C and D Planning Criteria Likelihood Consequences Credible and Acceptable Unlikely and Acceptable Unlikely and Extreme consequences Credible and Unacceptable 0 Generator Outage N-1 Line Outage N-2 Line Outage Extreme Events Deterministic Criteria D A B C Category of Contingencies, A, B, C and D

5. Online Reliability Monitor of Standard Contingencies & Potential Cascading Modes Likelihood Consequences Credible and Acceptable Unlikely and Acceptable Unlikely and Extreme consequences Credible and Unacceptable 0 Generator Outage N-1 Line Outage N-2 Line Outage Extreme Events Deterministic Criteria Potential Cascading Modes A B C D Category of Contingencies

6. Normal Weather Risk Exposure to One Cascading Mode With 1 Line on Maintenance Outage & System (6750 MW Load) Not Compliant with N-1 PRI = 150 MW PRI = 90 MW PRI = 50 MW PRI = 25 MW Initiating Event Tier 1 Cascade Tier 3 Cascade PRI = 200 MW Tier 2 Cascade

7. Storm Increases Risk Exposure to One Cascading Mode With 1 Line on Maintenance Outage & System (6750 MW Load) Not Compliant with N-1 PRI = 150 MW PRI = 90 MW PRI = 50 MW PRI = 25 MW Initiating Event Tier 1 Cascade Tier 3 Cascade PRI = 200 MW Tier 2 Cascade