WECC Planning CommitteeUnderfrequency Load Shedding

Review Group Update

March 25, & 26, 2014

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Underfrequency Load Shedding Review Group (UFLSRG)

• Philip Augustin Richard Hydzik Jerry Rust• Kent Bolton Danny Johnson Hari Singh• Desmond Chan Gerald Keenan Dede Subakti• Eleanor EwryStephanie Lu Branden Sudduth• Roy Gearhart Grace Martinez Shilpa Toppo• Irina Green Chris Pink Mike VanRemoortere• Mark HansonSteve Rueckert Gregory Vassallo

UFLSRG

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Devices respond to a frequency changeo Frequency sensitive load – motorso Frequency sensitive generation – governorso Automatic Generation control – AGCo Contingency Reserve Deployment – generation,

curtailment interruptible load, etc.o Other measures

After a disturbance – loss of generation - what happens?

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59.9

59.92

59.94

59.96

59.98

60

60.02

0 6 12 18 24 30 36 42 48 54 60

Typical Frequency Event WECC (Average of 5 events, T-5 to T+60)

Seconds

Typical WECC Frequency Excursion

Point C

Point A

Point B

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If frequency is still declining then what?

After a disturbance – loss of generation - what happens?

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Purpose of UFLS

Last automatic protection scheme to arrest the frequency decline after a disturbance

Load Shedding Occurs; Frequency decline was arrested; and, Recovery was observed.

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oUFLS Plan is to protect against cascading resource loss

oWECC RAS 1 is a separation Scheme – COI and Four Corners North Island South Island

UFLSRG Concepts to Remember

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o PRC-006-1 Broken down into these Requirements Joint review including historical events - E.B.1 Identified Island – E.B.2 A Regional UFLS Plan & simulation - E.B.R3.

through R5.• Adopted by the WECC Board

A Regional UFLS Data Base – R6. thru R9.• Established through PRC-006-WECC-CRT-1

UFLSRG

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Simulation of the Plan Once every 5 years - By November 1, 2014 (first year) – E.B.4

• UFLSRG Identified Islands and Scenarios E.B.1 & E.B.2 based upon prior simulations and Southwest Outage

• 14 different scenarios

UFLSRG

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o Simulation and Report Findings WECC technical review and formatting – will be posted for review –

approval at July meetings• Performance of the various UFLS settings demonstrated the applied

relays will provide adequate protection for the resource losses totaling up to 25% or greater in the defined islands

• Frequency excursion will experience conditions that would have 58.0Hz encroached but not passed

• Studies illustrated that the frequency arrestment utilized the full 5-step load shed and resulted in acceptable trajectory for frequency recovery

• In some cases, a few of the island configurations are showing 15-seconds anti-stalling features being engaged.

UFLSRG

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o Islands Simulated WECC North Island (Canada, further separation Alberta) South Island SW Outage event and all combinations

UFLSRG

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UFLSRG

1. 59.5 SILT ----- (~3,200 MW)2. 59.3 NW 5.6%3. 59.2 NW 5.6%4. 59.1 WECC other 5.3%5. 59.0 NW 5.6%6. 58.9 WECC other 5.9%7. 58.8 NW 5.6%8. 58.7 WECC other 6.3%9. 58.6 NW 5.6%10. 58.5 WECC other 6.7%11. 58.3 WECC other 6.7%

2014 current WECC Plan

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Case-Islands

14HS4island Pgen Pload PSched 10% 15% 20% 25%

WECC 173,594 167,475Neutral0 16,747 25,121 33,495 41,869

NORTH 76,655 67,167Export 6,445 13,162 16,520 19,878 23,237

SOUTH 96,939 100,307Import-6,445 3,586 8,601 13,616 18,632

Feb 2014

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MSSC LossArea Area_Name unit Pmax

54ALBERTA

Genesee 500

14ARIZONA

Palo Verde12 2756

50B.C.HYDRO

Revelstok345 1,505

11EL PASO

Riogd_G8 150

60IDAHO

Brownlee 5 259

21IMPERIALCA

El Steam 4 80

26LADWP

Scatt3g 460

20MEXICO-CFE

LRP-u4 290

62MONTANA

Colstrip 800

18NEVADA

HigginS3 330

10NEW MEXICO

San Juan 4 544

40NORTHWEST

CGS 1150

65 PAC J Bridger 12 1100

30PG AND E

Diablo Canyon

1200

70PSCOLORADO

Comanche3 805

22SAN DIEGO

Encina 5 329

64SIERRA

Valmy G2 300

24SOCALIF

Ormond2 750

52FORTISBC

Waneta 120

73WAPA R.M.

MBPP-1 605

63WAPA U.M.

Ft Peck 108

WECC 14,141 MWN-Island 6,647 MWS-Island 7,494 MW

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Project LossArea Area_Name Project Loss Pmax

54ALBERTA

Genesee 1,371

14ARIZONA

Palo Verde 4,132

50B.C.HYDRO

Gordon Shrum

2,830

11EL PASO

Newman6 288

60IDAHO

Brownlee 746

21IMPERIALCA

El Steam 263

26LADWP

Inter Mtn 1,900

20MEXICO-CFE

Pres. Juarez 1,128

62MONTANA

Colstrip 2,306

18NEVADA

Lenzie 1,170

10NEW MEXICO

San Juan 1,834

40NORTHWEST

Coulee 3ph 4,598

65PAC

J Bridger 2,200

30PG AND E

Diablo Canyon

2,400

70PSCOLORADO

Comanche 1,530

22SAN DIEGO

Encina 946

64SIERRA

Valmy 565

24SOCALIF

Ormond 1,500

52FORTISBC

Waneta 480

73WAPA R.M.

Craig 1,374

63WAPA U.M.

Ft Peck 108

WECC 33,344 MWN-Island 16,409 MWS-Island 16,935 MW

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o Performance The WECC Plan performed as designed under simulations

Load Shedding Occurs; Frequency decline was arrested; and, Recovery was observed.

UFLSRG

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o SW Outage Events Initial outage exceeded the 25% resources loss of the

UFLS Plan, therefore not a credible island for UFLS – beyond standard requirements

oCanada and Alberta During the past 10 years these islands have not formed

due to an underfrequency event.

UFLSRG

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oReview of the last unplanned large loss of generation

o June 14, 2004

UFLSRG

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Disturbance Overview

June 14, 2004 at 0741 MST

Westwing 500 kV / 230 kV and Palo Verde 500 kV subs cleared

Generation Tripped - 4610 MW’s

Load Interrupted - 996 MW’s

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Event Summary

Bird Excrement Caused Fault on Westwing-

Liberty 230 kV Line

Westwing WW1022 breaker failed to trip

(single point of failure – Auxiliary Relay)

APS System Operators thought WW 1022

breaker was in the open position during

restoration

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Frequency ChartFrequency(HZ)

59.5

59.6

59.7

59.8

59.9

60

60.1

7:37

:55

7:40

:48

7:43

:41

7:46

:34

7:49

:26

7:52

:19

7:55

:12

7:58

:05

8:00

:58

TIME

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Generation Tripped

Palo Verde Units 1, 2 & 3 3796 MWPalo Verde Units 1, 2 & 3 3796 MW

Red Hawk Units 1 & 2 206 MWRed Hawk Units 1 & 2 206 MW

Duke Arlington Unit 1 420 MWDuke Arlington Unit 1 420 MW

Other Units Other Units 188 188 MW MW

TotalTotal 4610 MW4610 MW

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System Restoration

• System Frequency recovered within 16 minutes

• COI was over its OTC limit for 13.5 minutes

• APS and SRP SOs focused on getting power to Palo Verde

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o Islands Simulated E.B.1 & E.B.2 - Planning Coordinators shall

participate and identify one or more islands to serve as the basis…

oUFLSRG has reviewed the past 10 years and configuration of the Western Interconnection

UFLSRG Future 2014-15

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o Proposed Islands to be Simulated 2014-15 WECC North Island South Island

UFLSRG

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oUFLS Review Group leadership To quote Forrest Gump “ I’m not a smart man” Volunteered for one year in 2008

o Transferring leadership to Chris Pink

UFLSRG

Questions?