electric utility solutions: modeling cold load pickup
Post on 18-Oct-2014
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DESCRIPTION
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: [email protected].TRANSCRIPT
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Agenda
• Traditional methods of analysis• Un-diversified load allocation• Emergency capacity determinations• Voltage drop analysis• Examples
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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.
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2008 Ice Storm
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2009 Ice Storm
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Inland Hurricane…or Derecho?
SouthEastern’sService Territory
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“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
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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?
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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
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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.
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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
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Determine capacity of conductor
• Emergency ampacity of overhead conductor:
• Emergency ampacity using 100˚C conductor temperature (no change in ambient)– 122% @ 25 C˚ Ambient– 131% @ 40 C˚ Ambient
old ambient,old cond,
new ambient,new cond,oldnew TT
TTII
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Determine capacity of conductor example
• Emergency ampacity of 4/0 ACSR in 0˚C (32˚F) ambient
• Emergency ampacity of #2 ACSR in 38˚C (100˚F) ambient
%14135750525750100357505
AA
AA
257538100184205
AA
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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
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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
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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
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Dixon Springs before
Normal peak current 68A
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Dixon Springs updated
Three phase project
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Carter south feed
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Elizabethtown before
Closing this sectionalizer
Would open this recloser
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Elizabethtown updated
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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.”