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ELECTRIC POWER GRID INTERDICITION

Javier Salmeron and Kevin Wood, Naval Postgraduate School

Ross Baldick, University of Texas at Austin

Sponsored by DoJ, Office of Domestic Preparedness

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Purpose

In this presentation we will...

• Show the importance of analyzing vulnerabilities of electric

power systems to terrorist attacks

• Present our models, and exact and heuristic algorithms to

carry out this analysis

• Present results on standard IEEE Reliability Test Networks

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“One can hardly imagine a target more ideal than the U.S. domestic

energy” (A.B. and L.H. Lovins, 1983)

“Any U.S. region could suffer lasting and widespread blackouts if three or

more substations were targeted.” (OTA, 1990)

“The U.S. is at, or is fast approaching, a crisis stage with respect to

reliability of transmission grids.” (NERC, 2001)

“The U.S. electric power systems must clearly be made more resilient to

terrorist attack.” (Committee on Science and Technology for Countering

Terrorism, NRC, 2002)

A Long-Recognized Issue (I)

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(On Ahmed Ressam) “They were specifically trained to attack critical

infrastructure, including electric power plants.” (CNN, 2002)

“And the threat isn't simply academic. U.S. occupation forces in

Afghanistan discovered Al Qaeda documentation about the facility that

controls power distribution for the eastern U.S., fueling fears that an attack

on the power grid may one day become a reality.” (Energy Pulse, 2003)

“Blue Cascades” project (simulated terrorist attack on the Pacific

Northwest's power grid). The study showed that such an attack, if successful,

could wreak havoc on the nation's economy, shutting down power and

productivity in a domino effect that would last weeks. (Energy Pulse, 2003)

A Long-Recognized Issue (II)

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Terrorist Threat

Potential targets:

Generating plants

Transmission and distribution lines

Substations

Easy disruption + Widespread damage + Difficult recovery

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• Assumes Information Transparency: Same information is available to both sides

• Uses optimization to assess worst-case disruptions

• Goal:

To provide insight on physical vulnerabilities and protective plans that proactively hedge against disruption caused by terrorist attacks

Our Approach

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In order to better defend the electric grid it is valuable to understand how to attack it!

- Optimal power flow model (minimizing load shedding)

- Interdiction model (maximize disruption)

Additional features of the problem are:

- Time scale: Very short-, short-, medium- and long-term

- Customer types; ability to “share the pain”

- Uncertainty about terrorist resources

- Assumptions on protection resources

Mathematical Analysis of the Problem

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, , ,min

Gen Line

Gen Shedic ic

g i cP P S

c c

Geng i cP SDC-OPF:

i: bus, l: line, g: generator, c: customer sector

PLine, PGen: power (MW) S: power shed : bus phase

Power Flow Model (DC Approx.)

( ) ( )( ),Linel o dl l lB P l L

| ( ) | ( )

( ),i

i cg G l o l i l d l i c

d

Gen Line Lineg l l i cP P P S i

,Line Linel lP P Line

lP l L

,Gen Geng gP P Gen

gP g G

0 ,i cd i cS ,i c

s.t.

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, ,max ( )

Gen Line BusG

Gen Line Busδ ,δ ,δI-DC-OPF:

* * *i

Line Busl

Gen Line Busg l i

i I g G L i Ii

l

M M M M

Gengδ δ δ

All {0,1}δ

, , ,( ) min

Gen LineP P S

Gen Shedic ic

g i c

G c c

Geng i cP SGen Line Busδ ,δ ,δ

Line Linel lP P Line

lP

Etc...

Where:

DC-OPF

Interdiction Model

s.t.

( ) ( )( )Linel o l d llB P

after

interdiction

(1 ) (1 ),Line Linel l δ δ

( ) ( )(1 )(1 )Bus Buso l d l δ δ(1 )Line

l δ

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Solve the DC-OPF Power Flow Model given the

current grid configurationBased on the current and previous flow patterns, assign a “Value” (V) to each interdictable asset Interdict the assets that

maximize “Total Value”

Heuristic

* * * *, ,

, , , ,

L I S,

maxGen Line

Bus Sub

Gen t Line t Gen tGen Line Gen Subg l i s

Sub tg l i s

g l i s

V V V V

δ δδ δ

* *

, ' , '

, ' , '

| |ˆ ˆ1 1

1, 1, ....

ˆ ˆs.t. ( ) ( ) ...... 1,

Line t Bus til

Line Bus Bus Subl i

Line t Bus t

i s

Line Busll i

l ii t t

L I

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Exact Linearization of the Modelmax min

( ) 0s.t.

0

,P

c

g

P

P

P

12 1 2( )(1 )(1 )a bP B 12 1 2

12 1 2

( ) ( ) ( )

( ) ( ) ( )

a b

a b

B

B

P

P

MM

(1 )

0

0

v

v

v v

v

max max

s.t. A ( )

b

P

b

c

, ,MIP : max

A

s.t.

{0,1}

v

vb b

c

B v d

v

C D

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Salmeron, Wood and Baldick (2004), IEEE Transactions on Power Systems

Interdiction resource: 6 terrorists

Line x1

Single transformer x2

Bus or substation x3

Total load: 2,850 MW

Load shedding: 1,258 MW

Load shedding: 1,373 MW

IEEE Reliability Test System 96-99

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Salmeron, Wood and Baldick (2004), IEEE Transactions on Power Systems

Load: 5,700 MW12 terrorists

Shedding:

2,516 MW

IEEE Reliability Test System 96-99

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$ ($ / )t

MWh MW dt

t(Attack)

MW shedding

One to several days

No repairDays to one week

Lines Trafos with spares

>1 months

System Restoration

Weeks

Slow repair

7683YESSubstations

N/AN/ANOGenerators

3603YESBuses

7682YESTransformers

N/AN/ANOLines (underground)

721YESLines (overhead)

Outage Duration (h)

Resources M (no. of

terrorists)

InterdictableGrid Component

E.g.:

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Salmeron, Wood and Baldick (2004), IEEE Transactions on Power Systems

Total Load: 2,850 MW

Time Power Energy

Period Shed (MW) Shed (MWh)

0-72 h 1,373 98,856

Plan

Total: 98,856 MWh

2

t

MW

+72hAttack

0-72 h 902 64,944

72-768 h 708 492,768

Total: 557,712 MWh

3 3+768h

IEEE Reliability Test System 96-99

SubstationProtected

SubstationProtected

0-360 h 756 272,160

Total: 272,160 MWh

4+360h

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Results for the Linearized MIP

Case/Algorithm Directly Interdicted Components TimePeriod

PowerShed (MW)

EnergyShed (MWh)

RTS-Two-Areas (M=24)HEURISTIC

Buses: 116, 118, 215, 218Substations: Sub-A1, Sub-A2, Sub-B1, Sub-

B2

0-360 h 2,693 969,480

360-768 h 1,416 577,728

Total: 1,547,208

RTS-Two-Areas (M=24)

MIP

Lines: A30, A33-2Transformers: A7, B7

Buses: 115, 118, 215, 218Substations: Sub-A2, Sub-B2

0-72 h 3,164 227,808

72-360 h 2,716 782,208

360-720 h 1,416 577,728

Total: 1,587,744

Case/Algorithm Directly Interdicted Components TimePeriod

PowerShed (MW)

EnergyShed

(MWh)

RTS-Two-Areas (M=12)HEURISTIC

Substations: Sub-A1, Sub-A2, Sub-B1, Sub-B2

0-768 1,416 1,087,488

Total: 1,087,488

RTS-Two-Areas (M=12)

MIP

Lines: A23, B23Transformers: A7, B7

Substations: Sub-A2, Sub-B2

0-72 h 1,804 129,888

72-768 h 1,416 985,536

Total: 1,115,424