APPA Engineering and Operations Technical Conference Atlanta, Georgia April 13-18, 2007 “Nailing the Basics” Earns Princeton, IL RP3 Diamond Award Jason Bird – City of Princeton, IL Ron Till – S&C Electric Company April 16, 2007

2 Background

3 Background  County Seat of Bureau County Illinois  Area about 7.0 mi 2  Population about 7,500 (2000)  City Owned Electric and Telecom Utilities  19 Electrical and Power Plant Employees

4 Background  Approximately 4,300 Customers  12 distribution circuits  70% overhead line  30% underground

5 Background  Receives bulk power at 138 kV  2 major substations:  138 kV => 34.5 kV and kV  34.5 kV => kV and 2.4 kV  Eight (8) multi-fuel engine-generators sets Used for summer peak shaving or export

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7 The Challenge  Major substation upgrade planned, but City didn’t have proper information to specify equipment or implement protection settings  Short-circuit study required  Coordination study required

8 The Challenge  Nearly 80% of the time transformer primary fuse, line fuse, and feeder breaker would operate  No reclosing relay on feeder breakers meant extended outages to Customers for transient faults  Need to improve reliability to Customers

9 The Solution  S&C engineers spent 2 days in the field collecting data for the studies. Nameplate information Line conductor sizes, configurations and lengths Verified existing system maps Review existing transformer and line fusing practices

10 The Solution  An accurate model of the City’s distribution system was constructed Ran short-circuit studies in compliance with ANSI C37 standards to evaluate fault currents with and without generation Conducted coordination studies with and without influence of generation

11 Study Results  Indicated that the overcurrent protective devices were applied within their ratings with 38 MW of local generation off-line, but…...  Fault currents on the kV system exceeded 18 kA (sym.) when on-line  Existing OCB’s in station and distribution class cutouts potentially over-dutied

12 Study Results  New breakers in substation would cover the interrupting ratings while generation was on-line….but devices beyond substation would not  Coordination study confirmed that high available fault currents made coordination with existing devices difficult

13 Proposed Changes  Evaluate ratings of distribution class cutouts  City was already using Positrol ® Fuse Links, so for purposes of establishing interrupting ratings, assumed Type XS Open Cutouts had been applied universally on system  Largest fuse link in inventory was 100 Amperes, so two styles of cutouts to choose from:

14 Proposed Changes Type XS Fuse Cutout Extra-Heavy-Duty Style  100 A Max.  14.4/15.0 kV Nom./Max.  110 kV BIL  12.0 kA, Asym.*  8.6 kA, Sym.* * one-shot rating, based upon replacement of cutout tube

15 Proposed Changes Type XS Fuse Cutout Ultra-Heavy-Duty Style  100 A Max.  14.4/15.0 kV Nom./Max.  110 kV BIL  16.0 kA, Asym.  10.6 kA, Sym.

16 Proposed Changes  With generators off-line, Extra-Heavy-Duty Style cutouts were capable of interrupting fault currents on any feeder when they were placed a minimum of 1,000 circuit-feet away from the substation  Considered fault duty and X/R ratio ANSI C – EHD tested at X/R = 8 – UHD tested at X/R = 12

17 Proposed Changes  However, when the generators are on-line, the available fault currents are too high….need to go with Ultra-Heavy-Duty Style cutouts or even Power Fuses close to or in the substation

18 Proposed Changes SMD ® -20 Power Fuse Overhead-Pole Top Style  200 A Max.  17.0 kV Max.  kV BIL  22.4 kA, Asym.  14.0 kA, Sym.

19 Proposed Changes SMD ® -40 Power Fuse Station-Vertical Style  400 A Max.  17.0 kV Max.  110 kV BIL  40.0 kA, Asym.  25.0 kA, Sym.

20 Proposed Changes Fault Tamer ® Fuse Limiter  20 A Max.  15.0 kV Max.  kV BIL  12.0 kA, Sym.  15,700 Max. I 2 t

21 Proposed Changes  Listed the minimum number of circuit-feet and geographic locations for the application of each type of device with the generators on-line

22 Benefits  Protective devices applied within ratings  Standardization of protective devices / switches  Reliability has gone up  Customer satisfaction has increased  More time to perform maintenance / inspections

23 Study Results  Start by standardizing transformer fusing  One simple chart for line crews  Minimize stock on trucks  Then select line fusing criteria

24 kVA Ratings S&C Standard Speed (TCC No ) S&C "K“ Speed (TCC No ) S&C "Fault Tamer” (TCC No ) Single-PhaseThree-PhaseFLA Fuse Link (Amperes) Fuse Link (Amperes) Fuse Cartridge (Amperes) K K K K K K K K K K K K- * conn. Δ-Δ, Δ- Y, and Y-Y

25 Existing Settings

26 Alternate Settings

27 Benefits  Significant reduction in outages  Smaller areas affected by outages when they do occur  Only 27% of time transformer fuse takes out line fuse  Better fusing schemes  Customer satisfaction has increased  Breaker lockouts have been significantly reduced