Chanan Singh Texas A&M University PSERC Webinar November 22, 2016

Transcription

1 Chanan Singh Texas A&M University PSERC Webinar November 22,

2 Modern power systems: integration of current carrying components (for power delivery), monitoring, computing, communication and protection systems. Human interface - power systems are not fully automated Complexity is increasing with more monitoring, control and communications Sources of failure: physical components ( power/current carrying), failures in cyber network hard and soft, human failures Contemporary power system reliability methods focused almost entirely on the failure of physical components 2

3 Analytical methods: mostly used in single, multiarea and distribution system models. Monte Carlo simulation; mostly used in multi-area and composite system models. Intelligent search techniques: still in development stage for either increasing the efficiency of analytical or simulation or providing an alternative to Monte Carlo simulation. Hybrid: mixing for increased strength. An assumption running through the developed models and methods is that of independence of components and that cyber part is perfectly reliable. 3

4 Power systems of the future are emerging to be different. Two major factors contributing to this change: Large penetration of renewable energy sources Increasing complexity of cyber part. Installation of hardware for interactive relationship between the supplier and consumer will add to complexity and interdependency between the cyber and physical parts. Complexity and interdependency will introduce more sources of problems and make reliability analysis more challenging but also more essential. 4

5 Cyber-Physical Security and Reliability Cyber Security: Studies deliberate cyber attack scenarios, consequences, and prevention or mitigation strategies. Cyber Reliability: Studies intrinsic failure modes of cyber related components and their impact on power system reliability. Ultimately both impact the reliability of power supply but the two may require different modeling and methodology. 5

6 The concepts and approaches will be explained using an example of a substation. The problems, however, extend across the entire grid. 6

7 A 230 KV Bus C E G 9 9 I Physical Components (Power-Carrying Components): Transmission Lines Power Transformers B 2 D 5 F 7 69 KV Bus H Circuit Breakers J Process Bus 10 Cyber Components: ES ES ES ES CTs/PTs Line Transformer Bus Brkr. IED Brkr. IED Brkr. IED Brkr. IED Breaker Control Merging Units Process Bus An IEC based protection system for a kv substation Ethernet Switches IEDs 7

8 230 KV Bus 9 I B A C 4 E D ES Line 5 F 7 5 ES Transformer Process Bus ES Bus 6 7 ES Brkr. IED Brkr. IED Brkr. IED Brkr. IED Breaker Control G H 9 69 KV Bus J Type Fault Locations Associated Circuit Breakers Line A Breaker 1 B Breaker 2 I Breaker 9 J Breaker 10 Transformer E Breakers 4, 6 F Breakers 5, 7 Bus C Breakers 1, 3, 4 D Breakers 2, 3, 5 G Breakers 6, 8, 9 H Breakers 7, 8, 10 8

9 230 KV Bus 9 I A 1 1 C 4 E G 9 Analysis: Primary fault on Line A B 2 D 69 KV Bus 5 F 7 H J ES Line ES Transformer Process Bus ES Bus ES Brkr. IED Brkr. IED Brkr. IED Brkr. IED Breaker Control 10 *Other : One or more components of 1, Line Panel, CB1 fail to operate. Or Process Bus is in delay state Failure Modes Physical Components Affected Probability all good Only Line A Process bus failed Entire Substation Other* Line A and Bus C

10 Analysis: Primary fault on Line B Physical Components Affected Probability Only Line B Entire Substation Line B and Bus D Analysis: Primary fault on Line I Physical Components Affected Probability Only Line I Entire Substation Line I and Bus G Analysis: Primary fault on Line J Physical Components Affected Probability Only Line J Entire Substation Line J and Bus H

11 A KV Bus C 4 E G 9 9 I Analysis: Primary fault on Transformer E B D 5 F 7 H 69 KV Bus Physical Components Affected Probability Only E ES Line 5 ES Transformer Process Bus ES Bus 7 ES Brkr. IED Brkr. IED Brkr. IED Brkr. IED Breaker Control J Entire Substation E and C E and G E, C, and G

12 A 230 KV Bus C 4 E 6 G I Analysis: Primary fault on Bus C Physical Components Affected Probability B 2 D 5 F 7 69 KV Bus H Only C J Entire Substation Process Bus A and C ES ES ES ES Brkr. IED Brkr. IED Brkr. IED Brkr. IED C and D C and E Line Transformer Bus Breaker Control A, C, and D 2.31*10-10 A, C, and E 2.31*10-10 C, D, and E 2.31*10-10 A, C, D, and E

13 Representing interdependency for Reliability Analysis Cyber-Physical Interface Matrix (CPIM) Line A Line B Line I Bus H Consequent Events Matrix (CEM) Line A Event-1 Event-2 Event-3 Event-4 Line B Line I Bus H 13

14 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus 230 KV Bus 9 I A 1 C 4 E G B 2 D 5 F 7 H 69 KV Bus J 10 Process Bus ES ES ES ES Brkr. IED Brkr. IED Brkr. IED Brkr. IED Line Transformer Bus Breaker Control 14

15 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus Step 1: Set the initial state of all components as UP and set the simulation time t = 0. Step 2: For each individual component, draw a random decimal number z i between 0 and 1 to compute the time to the next event. TT ii = llnn(zz ii) ρρ ii Depending on whether the i th component is UP or DOWN, λ i or µ i is used in place of ρ i 15

16 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus Step 3: Find the minimum time, change the state of the corresponding component, and update the total time. T q = min TT ii, 1 ii NN The next transition takes place by change of state of the q th component. The total simulation time t is increased by T q. t = t + T q 16

17 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus Step 4: Change the q th component s state accordingly. For each component i TT ii = TT ii T q 17

18 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus Step 5: If the state of the q th component transits from UP to DOWN, which means a primary fault occurs on this component, then the cyber-physical interface matrix is used to determine if there are some subsequent failures causing more components out of service due to the cyber part s malfunction. 18

19 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus Draw another random decimal number y (0 < y 1) Line A Transformer E Bus H

20 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus How to determine the next transition time of Transformer E and Bus C? TT ii = llnn(zz ii) ρρ ii For Transformer E, use µ i in place of ρ i For Bus C, use µ i,exp in place of ρ i µ i,exp is an expedited repair rate, called switching rate 20

21 Composite system reliability evaluation with the use of cyber-physical interface matrix 230 KV Bus G1 G2 M N Q A C E G I K G3 G4 O P R B D F H J L 69 KV Bus Step 6: Perform a network power flow analysis to assess system operation states. Update system-wide reliability indices. Repeat steps 3 6 until convergence is achieved. 21

22 Composite system reliability evaluation with the use of cyber-physical interface matrix When the simulation finishes, system-wide reliability indices can be obtained. G1 G2 M N Q A 230 KV Bus C E G I K NN ss HH ii tt ii LLLLLLLL = ii=1 tt tttttttttt G3 G4 O P R B D F H J L NN ss RR ii tt ii 8760 EEEEEEEE = ii=1 tt tttttttttt (With the unit of MWh/year ) 69 KV Bus LLLLLLLL = LLLLLLLL 8760 (With the unit of hours/year ) N s H i t i t total R i Total number of iterations simulated; Equals 1 if load curtailment occurs in the i th iteration; otherwise it equals 0; Simulated time in the i th iteration, with the unit of year; Total simulated time, with the unit of year. curtailment during the i th iteration, with the unit of MW; 22

23 Illustrating the overall methodology on a standard test system RBTS Test System G1 G5 G6 6 G3 Bus 3 Generating Station 1 G2 3 G G7 G8 G9 Generating Station 2 Bus MW G10 G11 The size of this system is small to permit reasonable time for extension of cyber part and development of interface matrices. But the configuration of this system is sufficiently detailed to reflect the actual features of a practical system MW 20 MW Bus 5 40 MW Buses 3 5 are extended with cyber configurations 9 Bus 6 20 MW 23

24 G1 Generating Station 1 G5 3 G8 G9 Generating Station 2 G6 20 MW G10 G11 Extend bus 3 of the RBTS Test System with substation protection configurations. G3 G4 Line 6 Line 5 Line 4 Line 1 6 G G Bus 3 Bus MW 40 MW 20 MW Bus Bus 6 Process Bus 20 MW Line 1 Panel Line 4 Panel Line 5 Panel Line 6 Panel Physical part of the RBTS Extension with cyber part in Bus 3 24

25 6 G3 G2 G1 Generating Station 1 G5 3 G G7 G8 G9 Generating Station 2 7 G6 20 MW G10 G11 Extend bus 4 of the RBTS with substation protection configurations. Line 2 Line 8 Line 4 Line Bus 3 Bus MW 20 MW Bus 5 40 MW Bus 6 Process Bus 20 MW Line 2 Panel Line 4 Panel Line 7 Panel Line 8 Panel Physical part of the RBTS Extension with cyber part in Bus 4 25

26 6 G3 G2 G1 Generating Station 1 G5 3 G G7 G8 G9 Generating Station 2 7 G6 20 MW G10 G11 Extend bus 5 of the RBTS with substation protection configurations. Line 5 Line Bus 3 Bus MW 20 MW Bus 5 40 MW Line 9 Bus 6 Process Bus 20 MW Line 5 Panel Line 8 Panel Line 9 Panel Physical part of the RBTS Extension with cyber part in Bus 5 26

27 G1 G5 G6 Generation Variation 6 G3 Bus 3 Generating Station 1 G2 85 MW 3 G G7 40 MW G8 G9 Generating Station 2 Bus MW G10 G11 Unit Bu Rating Failure Rate MRT (hours) No. s (MW) ( /year) MW 9 20 MW Bus 6 Bus 5 Physical part of the RBTS Variation The hourly load profile is created based on the information in Tables 1, 2, and 3 of the IEEE Reliability Test System*. *IEEE Committee Report, IEEE reliability test system, IEEE Trans. Power App. and Syst., vol. PAS-98, no. 6, pp , Nov./Dec

28 Line 6 Line 5 Line 4 Line pp 1,1 pp 1,2 pp 2,1 pp 2,2 pp 1,nn pp 2,nn pp mm,1 pp mm,2 pp mm,nn Process Bus Line 1 Panel Line 4 Panel Line 5 Panel Line 6 Panel Analyze the cyber failure modes and consequent events and obtain the Cyber-Physical Interface Matrices (CPIM) for Buses

29 Results: The CPIM and CEM of Bus 3 The Cyber-Physical Interface Matrix (CPIM) of Bus 3 Fault Location Probabilities Line Line Line Line The Consequent Event Matrix (CEM) of Bus 3 Fault Location Events Line Line Line Line

30 Results: The CPIM and CEM of Bus 4 The Cyber-Physical Interface Matrix (CPIM) of Bus 4 Fault Location Probabilities Line Line Line Line The Consequent Event Matrix (CEM) of Bus 4 Fault Location Events Line Line Line Line

31 Results: The CPIM and CEM of Bus 5 The Cyber-Physical Interface Matrix (CPIM) of Bus 5 Fault Location Probabilities Line Line Line The Consequent Event Matrix (CEM) of Bus 5 Fault Location Events Line Line Line

32 G1 G5 G6 G8 6 G3 Bus 3 Generating Station 1 G2 85 MW 20 MW G Bus 5 G7 40 MW G9 Generating Station 2 Bus MW G10 G11 Utilize the results of the interface matrices, perform a Monte-Carlo simulation for the composite system, and obtain numerical results of system-wide reliability indices. 9 Bus 6 20 MW 32

33 6 G3 Bus 3 G2 85 MW 20 MW G1 Generating Station 1 G4 G MW Bus 6 Bus 5 40 MW G8 G9 Generating Station 2 G7 Bus 4 7 G6 20 MW G10 G11 NN Objective: yy = MMMMMM bb ii=1 subject to: Variables: θ, G, and C CC ii BBθθ + GG + CC = LL GG GG mmmmmm CC LL DDDDDD FF mmmmmm DDDDDD FF mmmmmm GG, CC 0 θθ 1 = 0 θθ 2 NNbb unrestricted Total number of variables: 3N b N b C C i BB G G max L D A θ F max Number of buses NN bb 1 vector of bus load curtailments curtailment at bus i NN bb NN bb augmented node susceptance matrix NN bb 1 vector of bus actual generating power NN bb 1 vector of bus maximum generating availability NN bb 1 vector of bus loads NN tt NN tt diagonal matrix of transmission line susceptances, with N t the number of transmission lines NN tt NN bb line-bus incidence matrix NN bb 1 vector of bus voltage angles NN tt 1 vector of transmission line power flow capacities 33

34 Brief Results Impact on Expected Energy Not Served (EENS) EENS (MWh/year) Δ If protection systems are perfectly reliable Considering protection malfunctions Bus N/A Bus % Bus % Bus % Bus % Bus % Overall System % 34

35 G1 Line 5 Line ES 1-1 ES ES 2-1 ES 2-2 Bus 1 Bus 2 ES 1-3 ES S1-L5 S1-L1 S1-L2 S2-L6 S2-L3 S2-L1 Line 1 Line 2 Line 3 Line ES 3-1 ES ES 4-1 ES 4-2 ES 3-3 Bus 3 Bus 4 ES S3-L4 S3-L7 S3-L2 S4-L3 S4-L8 S4-L4 Line 7 G4 Line 8 35

36 Two types of cyber link failures: (a) A link is unavailable due to packet delay resulting from traffic congestion or queue failure; (b) A link is physically damaged. Failure type (b) is relatively rare and thus only failure type (a) is considered in this research 36

37 G1 Line ES 1-1 ES 1-2 Line ES 2-1 ES Bus 1 ES 1-3 Bus ES ES 1-1 ES Line S1-L5 S1-L1 S1-L2 S2-L6 S2-L3 S2-L1 Line 1 Line 4 Bus 3 Bus ES 3-1 ES 3-2 ES Line ES 4-1 ES 4-2 ES ES S1-L5 S1-L1 S1-L2 21 Line 7 S3-L4 S3-L7 S3-L2 G4 Line 8 S4-L3 S4-L8 S4-L4 17 Reliability Data for Components Component Failure Rate Mean Repair Time (/year) (h) Circuit Breaker Merging Unit Ethernet Switch Line Panel Cyber Component Names and Meanings Component Name Meaning 1-1 Merging Unit 1 at Substation Merging Unit 2 at Substation Merging Unit 3 at Substation 1 ES 1-1 Ethernet Switch 1 at Substation 1 ES 1-2 Ethernet Switch 2 at Substation 1 ES 1-3 Ethernet Switch 3 at Substation 1 S1-L5 Line 5 Panel at Substation 1 S1-L1 Line 1 Panel at Substation 1 S1-L2 Line 2 Panel at Substation 1 37

38 Cyber Component Names and Meanings Component Name Meaning 1-1 Merging Unit 1 at Substation Merging Unit 2 at Substation Merging Unit 3 at Substation 1 ES 1-1 Ethernet Switch 1 at Substation 1 ES 1-2 Ethernet Switch 2 at Substation 1 ES 1-3 Ethernet Switch 3 at Substation 1 S1-L5 Line 5 Panel at Substation 1 S1-L1 Line 1 Panel at Substation 1 S1-L2 Line 2 Panel at Substation ES 1-1 ES ES S1-L5 S1-L1 S1-L For the link i, the time it takes for a packet to travel in the forward direction is a random variable denoted by t i.1 For the reverse direction, the random time is denoted by t i.2 For example: Consider Link 7, the time it takes for a packet to travel from ES 1-1 to ES 1-2 is denoted by t 7.1 From ES 1-2 to ES 1-1, the time is denoted by t

39 Cyber Component Names and Meanings Component Name Meaning 1-1 Merging Unit 1 at Substation Merging Unit 2 at Substation Merging Unit 3 at Substation 1 ES 1-1 Ethernet Switch 1 at Substation 1 ES 1-2 Ethernet Switch 2 at Substation 1 ES 1-3 Ethernet Switch 3 at Substation 1 S1-L5 Line 5 Panel at Substation 1 S1-L1 Line 1 Panel at Substation 1 S1-L2 Line 2 Panel at Substation ES 1-1 ES ES S1-L5 S1-L1 S1-L Consider the communication from 1-1 to S1-L1. There are two possible paths: and pp ffffffff = Pr[ tt tt tt 4.1 > TT tttttt aaaaaa (tt tt tt tt 4.1 > TT tttttt )] where T tsd is a predefined threshold delay value for the two paths. 39

40 ES 1-1 ES ES S1-L5 S1-L1 S1-L From 1-1 to S1-L1 21 pp ffffffff = Pr[ tt tt tt 4.1 > TT tttttt aaaaaa (tt tt tt tt 4.1 > TT tttttt )] 17 Similarly, with any two components specified as the two ends of a communication path, the path failure probability can be computed from the cyber link level parameters 40

41 ES 1-1 ES ES S1-L5 S1-L1 S1-L The detailed procedures are based on queueing theory and are beyond the scope of this research. These probabilities can be assumed directly at the path level. 17 From To Forward Path Failure Probability Reverse Path Failure Probability 1-1 S1-L S1-L S1-L S1-L S1-L S1-L S1-L S1-L S1-L

42 G1 1-2 Line ES 1-1 ES 1-2 Bus 1 ES 1-3 Bus 2 Line S1-L ES 2-1 ES 2-2 ES 2-3 S1-L1 S1-L2 S2-L6 S2-L3 S2-L1 Line 1 Line 4 ES 3-1 ES 3-2 Line Line ES 4-1 ES 4-2 Results The Cyber-Physical Interface Matrix Primary Fault Probabilities of Consequent Events Location Line Line Line Line Line Line Line Line Bus 3 Bus ES ES 4-3 The Consequent Event Matrix Line 7 S3-L4 S3-L7 S3-L2 G4 Line 8 S4-L3 S4-L8 S4-L4 Primary Fault Consequent Events Location Line Line Line Line Line Line Line Line

43 Stage 1: Substation Level Analysis Analysis at this stage can be performed locally at each substation and the computations can be performed offline. Stage 2: Composite System Level Analysis The results of CPIMs and CEMs can be directly utilized. Monte-Carlo simulation performed in this stage is generic and applicable for large power systems. The CPIM decouples the 2 stages of analysis, making the overall analysis more tractable. 43

44 Cyber-Physical Interactions Modeling This is only starting point More detailed models need to be developed. We need to consider inter-substation interactions Consider the interaction of physical on the cyber as well More automated analysis at the substation level. 44

45 Computational Methods Development Generally non-sequential Monte Carlo Simulation is preferred as a more efficient method of for reliability evaluation. Several variance reduction techniques like importance sampling have been developed to make it even faster, especially those incorporating the concept of cross-entropy. The efficiency of non-sequential MCS is based on the assumption of independence between the components, although limited dependence can be accommodated. 45

46 Because of interdependence introduced by cyber part it becomes difficult to use nonsequential MC and the associated variance reduction techniques. So we have used sequential MCS. We have also proposed a non-sequential MCS technique to solve this problem but more work is needed in this direction. 46

47 IEEE RTS Reliability Test System has served as a resource for the researchers and developers to test their algorithms and compare their results with others. Additional information about distribution has since been added. This test system does not have information on the related cyber part. A taskforce under the Reliability, Risk and Probability Applications Subcommittee (RRPA) is investigating adding configurations and data on the cyber part. 47

48 1. C. Singh, A. Sprintson, Reliability Assurance of Cyber- Physical Power Systems, IEEE PES General Meeting, July Yan Zhang, Alex Sprintson, and Chanan Singh, An Integrative Approach to Reliability Analysis of an IEC Digital Substation, IEEE PES General Meeting, July H. Lei, C. Singh, and A. Sprintson, Reliability modeling and analysis of IEC based substation protection systems, IEEE Transactions on Smart Grid, vol. 5, no. 5, pp , September H. Lei and C. Singh, Power system reliability evaluation considering cyber-malfunctions in substations, Electric Power Systems Research, vol. 129, pp , December H. Lei and C. Singh, Non-Sequential Monte Carlo Simulation for Cyber-Induced Dependent Failures in Composite Power System Reliability Evaluation, IEEE Transactions on Power Systems, (accepted for publication: DOI: /TPWRS ) 48

49 This presentation is based on the work of my students Yan Zhang and Hangtian Lei. The work reported here was supported in part by PSERC Project T

50 Chanan Singh 50