Impact of Signal Delay Attack on Voltage Control for Electrified Railways

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1 Impact of Sigal Delay Attack o Voltage Cotrol for Electrified Railways Hoag Hai Nguye 1 Rui Ta 1 David K. Y. Yau 1,2 1 Advaced Digital Scieces Ceter (Sigapore), Uiversity of Illiois at Urbaa-Champaig 2 Sigapore Uiversity of Techology ad Desig

11 trasportatio itrusios i 213 Voltage cotrol i tractio power systems Cyberated, safety-critical

2 otivatio 3 rd largest cluster of cyber-physical attacks 214 oscow derailmet [U.S. CERT / ICS-CERT, 213] [Image from USNews] Cyber-attacks o idustrial cotrol systems Dragofly, Stuet 11 trasportatio itrusios i 213 Voltage cotrol i tractio power systems Cyberated, safety-critical Voltage drop before oscow derailmet

3 Backgroud AC tractio power systems Up to 5 kv Substatios coected to utility grid or dedicated power grid Large voltage fluctuatios Trais: movig loads De-acceleratig trais: movig geerators Trai shift betwee sectios causes step chage

4 Backgroud AC tractio power systems Up to 5 kv Substatios coected to utility grid or dedicated power grid Large voltage fluctuatios Trais: movig loads De-acceleratig trais: movig geerators Trai shift betwee sectios causes step chage Cetralized cotroller Geerators or trasformers Tractio power grid Chagig power cosumptio of trais Comm. etworks Voltage sesors

5 Voltage Cotrol State-space model for multi-bus power grid [k] [k 1]+ Cu[k]+ B(q[k] q[k 1])

6 Voltage Cotrol State-space model for multi-bus power grid [k] [k 1]+ Cu[k]+ B(q[k] q[k 1]) substatio voltages geerator/trasformer voltages substatio reactive power draws

7 Voltage Cotrol State-space model for multi-bus power grid [k] [k 1]+ Cu[k]+ B(q[k] q[k 1]) substatio voltages geerator/trasformer voltages substatio reactive power draws aitai at omial whe qchages

8 Voltage Cotrol State-space model for multi-bus power grid [k] [k 1]+ Cu[k]+ B(q[k] q[k 1]) substatio voltages geerator/trasformer voltages substatio reactive power draws aitai at omial whe qchages Cotrol algorithm u[k] = αc 1 ( [k]) BIBO stable if < α< 2 Similar cotrols applied i practice

9 Sigal Delay Attack Cetralized cotroller Geerators or trasformers Tractio power grid Chagig power cosumptio of trais Comm. etworks Voltage sesors Cotroller uses old voltage measuremets u[k] = αc -1 ( [k τ])

10 Sigal Delay Attack Cetralized cotroller Geerators or trasformers Tractio power grid Chagig power cosumptio of trais Comm. etworks Voltage sesors Cotroller uses old voltage measuremets u[k] = αc -1 ( [k τ]) Network cogestio, time desychroizatio Easier tha data itegrity attacks

11 Impact of Attack o Stability System state trasform New state trasitio model [ ] ] [,, 1] [, ] [ ] [ y = τ L I I L α G s characteristic polyomial Stable: All roots i uit circle of comple plae = = + I I I G y G y L O L L ] [ 1] [ 1 = + + α λ λ τ τ

12 Impact of Attack o Stability System state trasform New state trasitio model [ ] ] [,, 1] [, ] [ ] [ y = τ L I I L α G s characteristic polyomial Stable: All roots i uit circle of comple plae = = + I I I G y G y L O L L ] [ 1] [ 1 = + + α λ λ τ τ u[] = αc -1 ( [ τ])

13 λ τ+1 λ τ + α= Stable Regio No closed-form solutios Jury test Stable regio of α alicious time delay τ

14 λ τ+1 λ τ + α= Stable Regio No closed-form solutios Jury test Whe o attack Faster covergece Smaller fluctuatio Stable regio of α alicious time delay τ

15 λ τ+1 λ τ + α= Stable Regio No closed-form solutios Jury test Whe o attack Faster covergece Smaller fluctuatio Stable regio of α alicious time delay τ Trade-off btw cotrol performace ad tolerable malicious delay

16 A Eample PowerWorld simulatios 37-bus power system 1 feeder buses uder voltage cotrol α=.8 Voltage deviatio (p.u.) α=.2 No attack Voltage deviatio (p.u.) α=.8 Time step k α=.2 τ= 2

17 Aalysis Verificatio Approimatios i system modelig Affect accuracy of stability aalysis Stable regio of α By Jury test By simulatios alicious time delay τ

18 Summary ad Future Work Stability coditio of voltage cotrol uder sigal delay attack Trade-off betwee Voltage covergece speed whe o attack Tolerable time delay i terms of stability Future work Other voltage cotrol approaches Attack mitigatio

from definition we note that for sequences which are zero for n < 0, X[z] involves only negative powers of z.

from definition we note that for sequences which are zero for n < 0, X[z] involves only negative powers of z. We ote that for the past four examples we have expressed the -trasform both as a ratio of polyomials i ad as a ratio of polyomials i -. The questio is how does oe kow which oe to use? [] X ] from defiitio