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Substation Equipment
Maintenance
APPLICATION OF STATISTICAL METHODS
AMERICAN TRANSMISSION COMPANY
Does Standardization Improve Maintenance?
• American Transmission was formed when WI legislature prompted
electric utiliti...
Travel Times Vary Greatly at Each LDC
• Looking at the relationship of
travel times to distance
covered, there is an expec...
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TRAVEL
HOURS
TRAVEL DISTANCE
WPSC Wausau Tra...
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0.0 20.0 40.0 60.0 80.0 100.0 120.0
TRAVEL
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Alliant North Travel H...
BEFORE: wide variations in maintenance times
Procedure↓ Parameter→ n µ σ n µ σ n µ σ n µ σ
45 20 18 7
16.7 13.1 14.0 34.3
...
AFTER:
STANDARDIZATION
SHOWS
IMPROVEMENTS
After implementing standardized
maintenance procedures, we see
that variance has...
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Statistical evaluation of improvement gained through hypothetical standardization of maintenance across electrical substations. From MBA Statistics at Concordia University - Wisconsin.

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Statistical Evaluation of Standardization in Substation Maintenance

  1. 1. Substation Equipment Maintenance APPLICATION OF STATISTICAL METHODS AMERICAN TRANSMISSION COMPANY
  2. 2. Does Standardization Improve Maintenance? • American Transmission was formed when WI legislature prompted electric utilities to pool their facilities to form an independent transmission company. • Transmission facilities consist of power lines, substation circuit breakers and transformers. • Substation maintenance work is contracted back to the distribution companies which formed ATC. • The same shops which performed substation maintenance when the equipment was owned by the distribution companies perform the work for ATC. • Maintenance procedures are not currently standardized across ATC locations.
  3. 3. Travel Times Vary Greatly at Each LDC • Looking at the relationship of travel times to distance covered, there is an expection of medium to strong correlation (0.5 to 1.0) • This is not what was seen in reality: some sites actually had negative correlations. LDC Shop Coefficient of Correlation Alliant North -0.03 Alliant South 0.27 UPPCO Houghton 0.83 UPPCO Ishpeming 0.10 WE Fox Valley 0.60 WE Iron Range 0.48 WE Metro -0.36 WE North 0.65 WE South 0.40 WE West 0.40 WPSC Green Bay 0.04 WPSC Wausau 0.82
  4. 4. 0.0 2.0 4.0 6.0 8.0 10.0 12.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 TRAVEL HOURS TRAVEL DISTANCE WPSC Wausau Travel Hours
  5. 5. 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 TRAVEL HOURS TRAVEL DISTANCE Alliant North Travel Hours Prediction Line: Travel Hours = 3.964 hrs - 0.003 hrs/mile x Travel Distance
  6. 6. BEFORE: wide variations in maintenance times Procedure↓ Parameter→ n µ σ n µ σ n µ σ n µ σ 45 20 18 7 16.7 13.1 14.0 34.3 10.2 5.5 5.5 12.1 115 53 58 4 19.6 17.1 21.3 29.4 12.6 12.4 12.4 9.8 42 18 24 35.8 44.2 44.2 22.8 23.8 23.8 14 3 11 52.4 29.7 58.6 30.5 21.6 29.6 230 to 345 kV Breaker Diagnostics (SF6GasBreakers) Breaker Diagnostics (OilBreakers) Breaker Major (OilBreakers) Electric Test (NonLTCTransformers) All Voltages 069 kV 115 to 161 kV
  7. 7. AFTER: STANDARDIZATION SHOWS IMPROVEMENTS After implementing standardized maintenance procedures, we see that variance has been greatly reduced and there is clearly more variation in the 2011 results versus 2012. F-Test Two-Sample for Variances OLD 115 to 161 kv (2011) NEW 115 to 161 kv (2012) Mean 21.27655172 36.37931034 Variance 156.7613458 18.45009074 Observations 58 58 df 57 57 F 8.496508119 F Critical one-tail 1.55175754

Statistical evaluation of improvement gained through hypothetical standardization of maintenance across electrical substations. From MBA Statistics at Concordia University - Wisconsin.

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