1. Evolution of Cascading Failures in Power Transmission Systems OR How to turn off the lights Richard Wilson

2. What Next? The Problem Motivation My Approach Questions (from the peanut gallery) … and the gratuitous hurling of rotten fruitegitables

3. Problem Given a specific power network. Find the sequence of line outages which causes the most significant loss of service within the network.

4. Motivation – November 1965 blackout in the Northeast U.S., which cascaded system collapse in ten states. – 1967 Pennsylvania-New Jersey-Maryland blackout. – July 13, 1977 blackout in New York City. – July and August 1996 outages in the western U.S. grid. – August 14, 2003 blackout – August 28, London blackout – September 2003 Italian blackout – Associated Impact (dependant systems)

7. Motivation Lost productivity & $$$$$$ Inconvenience (subways) Darkness Looting & Riots Know your own weaknesses before your enemies learn them.

8. A BIG Problem Even for scaled systems search space is large IEEE 118 bus test system has 179 lines – 179! Possible line trip sequences – Explosive search space

9. Approach General EA design Representation Genetic Operators Fitness

10. General E.A. Design Tournament style parent selection (μ+λ) Survivor Selection Strategy Deterministic Selection

11. Sequence of lines to be outaged Uniqueness enforced Dynamic Size (/w arbitrary limit) { Line_4, Line_153, NONE, Line_12 } { 4, 153, 0, 12 } Representation

12. Genetic Operators Cut & CrossFill Recombination – Individuals may grow or shrink Uniform Mutation

13. Fitness - complications Requires data from multiple steady state evaluations Unknown time between steady states Various ‘levels’ of overload and associated time till failure per line

14. Fitness - simplifications Assumed steady states sufficient to capture ‘some’ failure scenarios. Used apparent power capacity of lines as measure of overload. Time to failure treated uniformly

15. Evaluation Evaluation process: Stable State Outage next line in Sequence Count outaged lines Calculate Load Loss Fitness Function

16. Fitness

17. Results Thus Far Modified Ward Hale 6 bus test System – Best individual so far: – { 0, 7, 4 } ≈ 9.06816 Not yet verified through brute force IEEE 118 test system just started

18. Additions or Future Work Dynamic Simulation of Event Sequences – Corrects for unknown time between steady states, but drastically lengthens fitness evals More than just Line outages Punctuated fitness evaluation Time till failure & Protection Devices FACTS Device enabled Power Network

19. Questions ? What is a FACTS Device? How big are FACTS Devices? How much do they cost? Are you worried about Homeland Security?

20. Thank You Give me an “A” You may now stop paying attention to me