Adverse Weather Risk Analysis in Power Systems
This 2019 study evaluates the impact of extreme weather events on power system reliability and whether utilities should invest in backup distributed generation.
Challenge
Increasing extreme weather events are causing more frequent and longer power outages, raising concerns about grid resilience.
Approach (Methods & Analysis)
1. Power System Modeling:
Created a small power system model consisting of a central generator, transmission lines, and distributed loads to simulate outages caused by adverse weather conditions.
Used Bonneville Power Administration (BPA) data to determine load demand and transmission distances.
2. Weather-Based Failure Conditions:
Categorized weather conditions into normal and adverse weather scenarios, with failure rates adjusted accordingly.
Defined transmission line and generator failure probabilities based on weather event severity.
Calculated unavailability, failure rate, and repair rate for system components using risk assessment equations.
3. Risk Indices & System Performance Metrics:
Evaluated the power system’s reliability using:
System Average Interruption Duration Index (SAIDI)
Customer Average Interruption Duration Index (CAIDI)
System Average Interruption Frequency Index (SAIFI)
Expected Demand Not Served (EDNS)
Computed these indices under four scenarios:
Normal Weather, 1 Generator
Normal Weather, 2 Generators
Adverse Weather, 1 Generator
Adverse Weather, 2 Generators
4. Impact of a Second Generator:
Compared the effect of adding a second generator on outage recovery times and load demand coverage during extreme weather conditions.
Key Findings & Insights
Severe Load Shedding in Adverse Weather Conditions
When only one generator was used, unmet energy demand increased significantly in adverse weather conditions.
The number of outages per customer exceeded 300 annually, with interruptions lasting over an hour on average.
Adding a Second Generator Reduced Outage Impact But Had Limitations
Introducing a second generator reduced power interruptions by half, but large loads remained unserved during extreme conditions.
While SAIDI and SAIFI values improved, they were still too high for acceptable grid reliability.
Backup Generation Did Not Improve Normal Weather Reliability
During normal conditions, adding a second generator did not reduce outage risks.
SAIDI and SAIFI increased, indicating the new generator introduced additional operational risks instead of improving grid stability.
Strategic Deployment of Additional Generation Recommended
Instead of permanent installation, the second generator should be deployed only during emergencies to minimize costs.
The utility could lease additional generation ahead of possible crisis periods instead of maintaining costly year-round backup power.