reliability assessment of smart grid considering direct cyber-power interdependencies

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Faculty of Engineering, Kasetsart University Mr.Wirote Buaklee July 31, 2012 Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

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Page 1: Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

Faculty of Engineering, Kasetsart University

Mr.Wirote BuakleeJuly 31, 2012

Reliability Assessment of Smart Grid Considering Direct Cyber-Power

Interdependencies

Page 2: Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

Selected Journal

B. Falahati, Y. Fu and L. Wu, “Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies”, IEEE Trans. Smart Grid, accepted June, 2012.

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Presentation Topics

I. Introduction

II. Definition of Cyber-Power Interdependencies

III. Cyber-Power Reliability Evaluation Algorithm

IV. Case Studies

V. Conclusion

Page 4: Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

I.Introduction

Smart grid initiatives are becoming more and more achievable through the use of information infrastructures that feature peer-to-peer communication, monitoring, protection and automated control.

The ever-increasing applications of cyber network might intensify the risk of failure and have adverse effects on the resilience of the power system.

Thereby, it is worthwhile to pay attention to the risk of failure in cyber systems for two particular reasons:

An increasing and sophisticated implement of cyber elements in the smart grid is introducing a higher risk of failure in the cyber-power system.

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I.Introduction

Failures in cyber elements are harder to trace than those in electrical power elements

Because of two networks are exhibit crucial differences, the conventional power system reliability analysis and evaluations are not applicable for interdependent cyber-power networks

This paper proposes a reliability assessment algorithm which can effectively consider the impact of cyber network failures on power networks especially in case of a direct cyber-power interdependencies

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II.Definition of Cyber-Power Interdependency

The “interdependency” generally means that “the correct and appropriate operation of one element depends on the existence and proper function of some other elements”.

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Interdependency can be classified into 4 types:

Direct element-element interdependencies (DEEI)

“Failures in a group of elements in one network either cause the failure of or change the specification of one element in the other networks”

Direct network-element interdependencies (DNEI)

“The performance of one network causes the failure of or changes the specification of the element in the other networks”

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II.Definition of Cyber-Power Interdependency

Page 8: Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

Indirect element-element interdependencies (IEEI)

“Failures of a group of elements in one network do not directly and immediately cause the failure of or change the behaviors of the element in the other network, but will impact the performance of the element against the potential Failure”

Indirect network-element interdependencies (INEI)

“The performance of one network does not directly and immediately cause the failure of or change the behaviors of the element in the other network but will impact the performance of the element against the potential failure”

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II.Definition of Cyber-Power Interdependency

Page 9: Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

A.Definitions

Three Concepts in proposed algorithm including:

1) P-Table

2) Cyber-Power Link(CP-Link)

3) State Mapping

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III.Cyber-Power Reliability Evaluation Algorithm

Page 10: Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

P-Table:

1) Index: 𝑖

2) System state, 𝜙𝑖

𝑘 = 𝑘𝑡ℎ element

𝑁𝐶 = Total number of element in cyber network

𝑁𝑃 = total number of element in power network

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III.Cyber-Power Reliability Evaluation Algorithm

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P-Table:

3) Probability, 𝑃𝑟𝜙𝑖

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III.Cyber-Power Reliability Evaluation Algorithm

𝐴𝑘 = Availability of element k

𝑈𝑘 = Unavailability of element k

𝜆𝑘 = failure rate of element k

𝜇𝑘 = Repair rate of element k

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CP-Link: a physical or logical relationship between the element 𝛾 in the cyber network and the element 𝛿 in the

power network.

if the cyber element 𝛾 fails or does not receive therequired data, the power element 𝛿 stops working.

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III.Cyber-Power Reliability Evaluation Algorithm

Page 13: Reliability Assessment of Smart Grid Considering Direct Cyber-Power Interdependencies

State Mapping: a procedure in which the probability of astate completely transfers to another state.

The state 𝜙𝑖 with failure of 𝐹𝐶 is mapped to another state𝜙𝑗 with failure of 𝐹𝑃.

The probability of power element failure(𝐹𝑃) is equal tothe probability of cyber element failure( 𝐹𝐶 ) plus theprobability of power element failure without cyberelement failure (𝐹𝐶

′)

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III.Cyber-Power Reliability Evaluation Algorithm

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B.Overview of Proposed Reliability Assessment Procedure

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III.Cyber-Power Reliability Evaluation Algorithm

1

2

3

D

E

C

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C. P-Table Creation

1. Initializing the P-Table

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III.Cyber-Power Reliability Evaluation Algorithm

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1. Initializing the P-Table: Example

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III.Cyber-Power Reliability Evaluation Algorithm

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III.Cyber-Power Reliability Evaluation Algorithm

𝑷𝒓𝟏𝟏 = 𝑼𝑪𝟏 × 𝑨𝑪𝟐 × 𝑨𝑪𝟑 × 𝑨𝑷𝟏 × 𝑼𝑷𝟐 × 𝑷𝑷𝟑

= 𝟎. 𝟎𝟑 × 𝟎. 𝟗𝟕 × 𝟎. 𝟗𝟖 × 𝟎. 𝟗𝟔 × 𝟎. 𝟎𝟒 ×0.98

3 97

2 98

4 96

2 98

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2. Integration of Equivalent States: combination all identical states as a unique state such as when a node fails all connected elements virtually and logically fail.

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III.Cyber-Power Reliability Evaluation Algorithm

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III.Cyber-Power Reliability Evaluation Algorithm

3 97

2 98

4 96

2 98

𝑷𝒓𝟒𝟓 = 𝟎. 𝟎𝟎𝟏𝟎𝟕𝟑 + 𝟎. 𝟎𝟎𝟎𝟎𝟐𝟏 + 𝟎. 𝟎𝟎𝟎𝟎𝟐𝟏

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III.Cyber-Power Reliability Evaluation Algorithm

3. State Mapping: map one state to another state base on DEEI and DNEI.

For example shows in Fig.4, the state 𝜙45 𝐶1, 𝐶3, 𝑃2, 𝑃3 will map to the state 𝜙47 𝐶1, 𝐶3, 𝑃1, 𝑃2, 𝑃3based on the CP-Link: D= (C1:P1)

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III.Cyber-Power Reliability Evaluation Algorithm

3 97

2 98

4 96

2 98

𝑷′𝒓𝟒𝟕 =0.001115+0.000044

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III.Cyber-Power Reliability Evaluation Algorithm

Connectivity Check of Cyber Networks With Multiple Data Sources:

by Linear Programming

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III.Cyber-Power Reliability Evaluation Algorithm

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III.Cyber-Power Reliability Evaluation Algorithm

𝑁𝑏 = required data source

𝛽𝑊 = 1 means DNEI in which the required data cannot be transferred to the data receiver 𝑟 cause the failure of power element 𝛿𝑊

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D. Load Shedding Evaluation of Power Systems

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III.Cyber-Power Reliability Evaluation Algorithm

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D. Load Shedding Evaluation of Power Systems

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III.Cyber-Power Reliability Evaluation Algorithm

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E. Reliability Indices Calculations

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III.Cyber-Power Reliability Evaluation Algorithm

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IV.Case Studies

𝐸𝑀𝑈 = 𝐸𝑛𝑒𝑟𝑔𝑦 𝑀𝑎𝑛𝑎𝑔𝑒𝑚𝑒𝑛𝑡 𝑈𝑛𝑖𝑡

Line capacity = 1.2 pu.Generator availability = 1

A. Testing System Description

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IV.Case Studies

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IV.Case Studies

B. Testing Results

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IV.Case Studies

Case 1

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IV.Case Studies

Case 1

“DNEI should be analyzed to achieve a more

accurate evaluation”

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IV.Case Studies

Case 2

“System reliability depends on the failure rate of

switches in cyber network”

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IV.Case Studies

Case 3

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IV.Case Studies

Case 3

“Higher cyber complexity with more switches does not

necessarily guarantee a higher reliability” thus, the

optimization algorithm is needed for cyber design

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V. Conclusion

The study only DEEI is not adequate for assessing the reliability of a cyber-power system.

The design of the cyber network affects the reliability of the power network.

The proposed algorithm can be applied for developing an optimization problem for the design of cyber network to achieve the higher level of reliability for the power network.

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