1. Copyright © SEL 2009 Then Versus Now: A Comparison of Total Scheme Complexity Bob Morris, Roy Moxley, and Christina Kusch Schweitzer Engineering Laboratories, Inc.

2. Simple- Scheme Fault Tree Analysis

3. Real-World Transmission Scheme Is More Complex

4. Leading to More Complex Fault Tree

5. Connections Are Part of Critical Path

6. Many Benefits to Reducing Yard Wiring

7. “Critical” Path Wiring Is Substantial Part of Total Wires

8. “Unavailability” Time Is Function of Multiple Inputs MTBF Detection time Time to repair

9. Mean Time to Failure 30–400 years Not “tested” into product Environmental impact

10. Detection Time Most important factor Self-test vs. scheduled test

11. Time to Repair How difficult is repair? What else is out of service during repair?

12. Guide to Fuse Replacement 97 A243 A612 A1482 A (Slow Blow)

13. Subcomponents and Adjustments Are Part of Scheme Complexity

14. Even Subcomponents Have Subcomponents

15. Microprocessors: More Components, Fewer Adjustments

16. Merging Unit Concept

17. Advanced CT Application Topologies MV and HV GIS Switchgear IEEE C37.92 IEC 61850-9-2

18. Ethernet IEC 61850: Switched Ethernet Station and Process Bus From Beginning

19. IEC 61850 Defines Suite of Protocols – Not Just One

20. Sampled Values on LAN Takes decentralization one step further Separates sampling physically from ♦ Measurement ♦ Metering ♦ Calculation Publishes constant message at predefined rate Sends SV to multiple subscribers

21. Traditional Topology: Wires Vs. Components

22. Relays in Yard: Fewer Wires, Where Do You Test?

23. Relay-Based Process Bus System

24. Merging Unit Reduces Wire Count, Increases Device Count

25. Moving I/O to Yard: Replace Wire With Fiber

26. Where Should Testing Be Performed?

27. It Is Colder (or Hotter) Outside

28. Conclusions Number of wires and number of devices are key elements of complexity Reduction of wire count AND device count both need consideration

29. Conclusions Firmware complexity and qualitative measures are as significant as hardware measures Measuring and evaluating scheme complexity are how we improve