1. SWEDE - April 26 th, 2011 - Bastrop Tommy Nylec Austin Energy Fusing and Fault Indicator Applications

2. 2 22 2 OverviewOverview  Introduction to Austin Energy  Purpose of Coordination Concern  Unique Situations  Engineering and Operational Solutions  Future Work and Conclusions

3. 3 33 3 Austin Energy Statistics  >400,000 Customers  >2,800 MW Generation  ># mi Transmission  56 Distribution Substations  > 10,000 miles of Distribution  >1,600 Employees  Serve 437 square miles including Austin city limits and neighboring areas  Started in 1887

4. 4 44 4 Austin Energy Reliability  SAIFI =.63  SAIDI = 43.97  CAIDI = 69.86  Challenge ourselves with high goals for reliability indices  Consistently in the top performance in the country

5. 5 55 5 Coordination Scheme Revisited  Need to be simple to interpret for field personnel  Must allow for ease of use in design environment  Application must hold in > 80% cases  Point of coordination determined by maximum available fault current  20% Separation between Total Clear and Minimum Melt curves of devices

6. 6 66 6 Austin Energy Fault Current Levels  Item of Concern  Infinite Bus Calculations for Larger Transformers= 14.5 kA  Short Feeders  High density of substations  System is primarily 12.5 kV  Transmission Impedance on larger transformers creates approximately 10 kA  Majority of fuses are at > 2kA  Typical Unit Installation results in Fault Current < 8.5 kA at Bus

7. 7 77 7 Warehouse Inventory  Limited space in warehouse and trucks  Minimize variety of fuses  Standardize applications  Reduction of inventory

8. 8 88 8 Substation Coordination  Most relays set at 360 A Ground Pickup  Eases coordination with downstream devices  Provides adequate system protection  Considerations  Some substations do not have this setting  Conflicts with some fusing scenarios

9. 9 99 9 Unique Scenarios  Slugging  Required due to presence of extra fuse  Fault Level Cheat Sheets  Rules of Thumb don’t apply  Skip fuse size between devices

10. 10 SolutionSolution  Keep same fuse ampacity ratings  Limit number of fuses with same ampacity but different speeds  Allow duplicates in most common sizes  Austin Energy Rule of Thumb  Must skip 2 fuse sizes between devices

11. 11 Feeder Coordination Studies  Studies performed on 5 year rotational basis  Creates opportunity to revisit coordination scheme  Allows adjustment of existing fuses to new scheme  Limited inventory restricts solutions to encountered problems

12. 12 Fault Indicator Application  Fault must pass through equipment  Placed accordingly  Follow Cooper Application guide

13. 13 Austin Energy Standard Traditional Placement:  Located at transformer Austin Energy Additional Requirements:  Additional F.I.’s located at risers and switchgears

14. 14 Installation Methods  Concentric Neutral  Identified misapplication  Changes made to standard to correct  In accordance with industry standards

15. 15 Fault Indicator Conclusions  Provide additional visual cues of fault locations  Decrease service restoration time  Reduce equipment exposure during restoration practices  Economic Impact

16. 16 Questions?Questions?