Underfrequency Load Shedding Assessment Report

Kent Bolton

January 30, 2014JGC Meeting SLC, UT

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• UFLSTF formed in 2009 by PCC & OCoReview effectiveness of Plan

• Designed to arrest declining frequency• Assist recovery of frequency after UFLS

events

Coordinated Plan

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• Coordinated Plan maintained since 1998 with last review in 2009

• UFLS data base developed through PRC-006-WECC-CRT-1

• UFLS relay data consistent with WECC Base Case data

• Several simulations evaluated – frequency in each case returned to safe operating range

Main Findings

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• Coordination exists within the Coordinated Plan

• Anti-stalling and overshoot in accordance with Coordinated Plan

Main Findings, cont.

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• 13hsp1a spring on-peak• 13hs2 summer on-peak• 13ls1 summer off-peak• 14hw2 winter on-peak• 14lw1 winter off-peak

Base Cases

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• WECC-WI Island (WI)• Canada Island (C)• North Island (N)• North Island w/o Alberta (NBF)• North Island w/o Canada (NWC)• AESO Island (A)• BC Hydro Island (BF)• South Island (S)• Imperial Valley Island (IV)• Mexico CFE Island (CF)

Islands

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• San Diego Island (SD)• San Diego Area Island w/ Mexico and Imperial Valley (SIC)• San Diego Area Island w/ Imperial Valley (SDI)• San Diego Area Island w/ Mexico (SDC)• Impact of Variable generation

Islands, cont.

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• Normal topologies exhibit successful demonstration of UFLS

• Including 25% imbalance cases, all frequencies recovered to > 58 Hz but not > 59.5 Hz

• 15-sec anti-stalling stage oDoesn’t increase recovery frequency

• 30-sec, 60-sec stages required?

Results

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• Abnormal topology – September 2011o San Diego, IV, CFE – 50% imports

• Variable Generation o Increased amounts impact freq. recovery

Results, cont.

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• Coordinated Plan is adequate in safety-net use and application

• Increased use of anti-stall component• WECC Base Case and program model

should be reviewed

Conclusions

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Plot

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• Assure automatically switched reactive devices are modeled

• Assure voltage regulators and PSS are correctly represented

• Review gen settings to assure correct representation

• Continue to annually simulate island scenarios

Recommendations

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• Load controller and governor settings in WECC base cases need review

• Review WECC base cases for accuracy under extreme events – long and short term

• Review initial stage load shedding and anti-stalling settings to determine if adjustments are necessary

Recommendations, cont.

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• Review simulation results to determine if Coordinated Plan needs modification

• Review V/Hz results and determine a defined method for measurement of performance

• Include composite load model in next year’s assessment

Recommendations, cont.

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• UFLSRG Mtg – SLC, Ut Feb. 18-19, 2014• 2014 Data Request

oGO Submittals due 6/1/14oUFLS Entity Submittals due 7/1/14

Next Steps

Questions?