Liisa Haarla (formerly Pottonen) worked on transmission system planning in Finland between the years 1985 and 2002. This work included grid planning, grid operation planning, different grid simulations and power system protection planning. This experience and understanding of the power system operations and dynamic performance enabled her to prepare research and make a doctoral thesis about power system security. In her thesis she presents a probabilistic method for estimating grid security after line faults. She is now professor of power transmission systems in Aalto University School of Science and Technology. Mikko Koskinen received an MSc in Electrical Engineering in 1985 and has extensive experience of power transmission grids. Since 1986 he has worked on numerous studies ranging from single network simulation tasks to grid master plans and development of the grid code. He is currently working as a senior specialist with the Finnish Transmission System Operator Fingrid.    Pierre-Etienne Labeau is working on the development of an integrated PSA methodology, combining dynamic simulations and discrete system state changes. Though his first field of application is in nuclear engineering, in recent years he has been involved in several Belgian projects on the maintenance and security of electrical grids. He is currently lecturer of reliability engineering and nuclear engineering in the Free University of Brussels. Ritva Hirvonen (Dr. Eng) has been working on power system issues from the beginning of 1980s. Her work has included power system planning and operation, as well as generation and grid interaction tasks. She has worked on these issues in industry, university and a research institute. In recent years, she has been working on European regulatory issues dealing with transmission and wholesale markets, and was recently head of unit in Finnish energy regulator, the Energy Market Authority. She is currently working as a development manager with the Finnish Transmission System Operator Fingrid.

• 1. Introduction.- 2. Grid Security — Problem Statement.- 3. Basic Concepts of Transmission Grid Planning.- 4. Basic Concepts of Reliability Theory.- 5. Grid Faults and Component Failures.- 6. Substation PSA Model.- 7. Dynamic Consequence Analysis.- 8. System level Results.- 9. Perspectives for Future Power System.- 10. Conclusions.

Liisa Haarla (formerly Pottonen) worked on transmission system planning in Finland between the years 1985 and 2002. This work included grid planning, grid operation planning, different grid simulations and power system protection planning. This experience and understanding of the power system operations and dynamic performance enabled her to prepare research and make a doctoral thesis about power system security. In her thesis she presents a probabilistic method for estimating grid security after line faults. She is now professor of power transmission systems in Aalto University School of Science and Technology. Mikko Koskinen received an MSc in Electrical Engineering in 1985 and has extensive experience of power transmission grids. Since 1986 he has worked on numerous studies ranging from single network simulation tasks to grid master plans and development of the grid code. He is currently working as a senior specialist with the Finnish Transmission System Operator Fingrid.    Pierre-Etienne Labeau is working on the development of an integrated PSA methodology, combining dynamic simulations and discrete system state changes. Though his first field of application is in nuclear engineering, in recent years he has been involved in several Belgian projects on the maintenance and security of electrical grids. He is currently lecturer of reliability engineering and nuclear engineering in the Free University of Brussels. Ritva Hirvonen (Dr. Eng) has been working on power system issues from the beginning of 1980s. Her work has included power system planning and operation, as well as generation and grid interaction tasks. She has worked on these issues in industry, university and a research institute. In recent years, she has been working on European regulatory issues dealing with transmission and wholesale markets, and was recently head of unit in Finnish energy regulator, the Energy Market Authority. She is currently working as a development manager with the Finnish Transmission System Operator Fingrid.

• 1. Introduction.- 2. Grid Security — Problem Statement.- 3. Basic Concepts of Transmission Grid Planning.- 4. Basic Concepts of Reliability Theory.- 5. Grid Faults and Component Failures.- 6. Substation PSA Model.- 7. Dynamic Consequence Analysis.- 8. System level Results.- 9. Perspectives for Future Power System.- 10. Conclusions.