Electric Utility Solutions: Modeling Cold Load Pickup

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Just another systems engineering and analysis presentation from Milsoft's 2009 User Conference. It was originally presented by Eric Jung. The Milsoft Electric Utility Solutions Users Conference is the premier event for our users and the vendors who provide interoperable utility management solutions or services that enhance Milsoft Smart Grid Solutions. If you’d like to be on our mailing list, just email: missy.brooks@milsoft.com.

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Electric Utility Solutions: Modeling Cold Load Pickup

  1. 1. Modeling Cold Load Pickup Eric Jung
  2. 2. Agenda • • • • • Traditional methods of analysis Un-diversified load allocation Emergency capacity determinations Voltage drop analysis Examples
  3. 3. What is Cold Load Pickup? • Cold load pickup is a loss of diversity following an extended outage. • “Cold” refers to the state of the load, not the ambient temperature. • Problems stem from thermostatically controlled loads.
  4. 4. 2008 Ice Storm
  5. 5. 2009 Ice Storm
  6. 6. Inland Hurricane…or Derecho? SouthEastern’s Service Territory
  7. 7. “Rule of thumb” Methods & Shortcomings • Assume 200%-300% of full load current – Only a 100% swing…Is that all? • Fails to take nature of load into account • Traditional methods require: – Normal peak data – Many assumptions
  8. 8. Requirements for modeling • Billing file with 15-minute interval data – With AMR data, this is no problem. – Without AMR data, this must be calculated. • Knowledge of operational characteristics of C&I customers – How will load ramp up after an outage? – What load will pick up immediately?
  9. 9. Un-diversified load allocation 1. Set sources to swing. 2. Set all load groups to “diversity fixed.” 3. CF % for residential should be 95%-100%. 4. C&I groups are variable. 5. Apply and Run
  10. 10. Emergency system capacity • The following capacities must be determined: – Short time overload capacity of substation transformer – Emergency conductor capacity – Overcurrent device capacity • Emergency voltage standards must be established.
  11. 11. Emergency capacity of sub transformer • FA 65˚C rating is 25%-40% above base • Short time overload of < 30 min – 50% pre-outage loading = 168% overload – 70% pre-outage loading = 158% overload – 90% pre-outage loading = 145% overload • Combined yield: – 181%-235% over base 55˚C rating
  12. 12. Determine capacity of conductor • Emergency ampacity of overhead conductor: Inew  Iold  Tcond, new  Tambient, new Tcond, old  Tambient, old • Emergency ampacity using 100˚C conductor temperature (no change in ambient) – 122% @ 25 C˚ Ambient – 131% @ 40 C˚ Ambient
  13. 13. Determine capacity of conductor example • Emergency ampacity of 4/0 ACSR in 0˚C (32˚F) ambient 100  0 505 A  357 A 75  25 505 A  357 A 141% • Emergency ampacity of #2 ACSR in 38˚C (100˚F) ambient   100  38 205 A  184 A 75  25
  14. 14. Determine capacity of system protection • Electronic Reclosers – Minimum phase trip setting – Ground trip must account for downstream single phase devices. – Windmill will base capacity on lowest Min Trip. • Hydraulic Recloser – Cooper reclosers reference R280-90-4 – Limit to 150% of series coil rating
  15. 15. Voltage drop setup: capacity • Set capacity colors to match emergency capacities. • Could use “Color by Custom.” – Allows further breakdown to fuse, OCR… – Allows multiple colors based on % over capacity
  16. 16. Voltage drop setup: voltage • ANSI C84.1-2006 • Range B standard – 91.7%-105.8% nominal • When is Range B tolerable? – Short term emergency conditions – Should be corrected as soon as possible to Range A
  17. 17. Dixon Springs before Normal peak current 68A
  18. 18. Dixon Springs updated Three phase project
  19. 19. Carter south feed
  20. 20. Elizabethtown before Closing this sectionalizer Would open this recloser
  21. 21. Elizabethtown updated
  22. 22. Principle Lessons Learned • System protection – Should be based on: • • • • – Capacity Fault current Cold load pickup Coordination Should not be based on: • • • Load current Some arbitrary minimum fault impedance The way we’ve “always done it.”
  23. 23. Contact info Eric Jung Engineering Manager SouthEastern IL Electric Co-op ericjung@seiec.com

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