Building a Combined 25F Nomogram Step 0: Define Terms

Safe operating area: System remains within limits following the next worst contingency, regardless of PSA generation levels.

Potentially safe operating area: Depending on PSA generation, the system may not remain within limits following the next worst contingency.

Unsafe operating areas: System WILL NOT remain within limits following the next worst contingency, regardless of PSA generation levels.

Danger area: blind spot: Depending on PSA generation levels, a specific contingency may cause a transmission element to exceed its limits. With current tools, the System Operators may not be aware of this risk.

Building a Combined 25F Nomogram Step 0: Define Terms

Safe operating area: System remains within limits following the next worst contingency, regardless of PSA generation levels.

Potentially safe operating area: Depending on PSA generation, the system may not remain within limits following the next worst contingency.

Unsafe operating areas: System WILL NOT remain within limits following the next worst contingency, regardless of PSA generation levels.

Danger area: blind spot: Depending on PSA generation levels, a specific contingency may cause a transmission element to exceed its limits. With current tools, the System Operators may not be aware of this risk.

Sensitivity of South-North Ingledow-Custer limits to PSE, SCL, and SNOH Generation

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

PSE Generation (MW)

Ing

led

ow

-Cu

ster

lim

it (

MW

)

S-N Westside Limit=2000 MW

S>N SCL+SNOH Gen= 140 MW

S>N SCL+SNOH Gen= 460 MW

S>N SCL+SNOH Gen= 775 MW

N-S Westside Limit=2850 MW"

Canadian Entitlment

Building a Combined 25F Nomogram Step 1: Import South-to-North Nomogram

Tacoma-Covington #2 230kV line O/S

Winter 2007

Heavy LoadsOutage: 931

Temp: 25Fahrenheit

Safe operating area

Potentially safe operating area

Unsafe operating areas

Danger area: blind spot

Sensitivity of South-North Ingledow-Custer limits to PSE, SCL, and SNOH Generation

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

PSE Generation (MW)

Ing

led

ow

-Cu

ster

lim

it (

MW

)

S-N Westside Limit=2000 MW

S>N SCL+SNOH Gen= 140 MW

S>N SCL+SNOH Gen= 460 MW

S>N SCL+SNOH Gen= 775 MW

N-S Westside Limit=2850 MW"

Canadian Entitlment

Building a Combined 25F Nomogram Step 2: Evaluate the S>N Operating Areas

Tacoma-Covington #2 230kV line O/S

Winter 2007

Heavy LoadsOutage: 931

Temp: 25Fahrenheit

Safe operating area

Potentially safe operating area

Unsafe operating areas

Danger area: blind spot

Sensitivity of South-North Ingledow-Custer limits to PSE, SCL, and SNOH Generation

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

PSE Generation (MW)

Ing

led

ow

-Cu

ster

lim

it (

MW

)

S-N Westside Limit=2000 MW

N-S Westside Limit=2850 MW"

S>N SCL+SNOH Gen= 140 MW

N>S SCL+SNOH Gen= 460 MW

N>S SCL+SNOH Gen= 775 MW

Building a Combined 25F Nomogram Step 3: Import & Invert North-to-South Nomogram

Tacoma-Covington #2 230kV line O/S

Winter 2007

Heavy LoadsOutage: 931

Temp: 25Fahrenheit

Safe operating area

Potentially safe operating area

Unsafe operating areas

Danger area: blind spot

Sensitivity of South-North Ingledow-Custer limits to PSE, SCL, and SNOH Generation

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

PSE Generation (MW)

Ing

led

ow

-Cu

ster

lim

it (

MW

)

S-N Westside Limit=2000 MW

N-S Westside Limit=2850 MW"

S>N SCL+SNOH Gen= 140 MW

N>S SCL+SNOH Gen= 460 MW

N>S SCL+SNOH Gen= 775 MW

Building a Combined 25F Nomogram Step 4: Evaluate the N>S Operating Areas

Tacoma-Covington #2 230kV line O/S

Winter 2007

Heavy LoadsOutage: 931

Temp: 25Fahrenheit

Safe operating area

Potentially safe operating area

Unsafe operating areas

Danger area: blind spot

Sensitivity of South-North Ingledow-Custer limits to PSE, SCL, and SNOH Generation

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

PSE Generation (MW)

Ing

led

ow

-Cu

ster

lim

it (

MW

)

S-N Westside Limit=2000 MWS>N SCL+SNOH Gen= 140 MWS>N SCL+SNOH Gen= 460 MWS>N SCL+SNOH Gen= 775 MWN-S Westside Limit=2850 MW"S>N SCL+SNOH Gen= 140 MWN>S SCL+SNOH Gen= 460 MWN>S SCL+SNOH Gen= 775 MWCanadian Entitlment

Building a Combined 25F Nomogram Step 5: Combine & identify blind spots

Tacoma-Covington #2 230kV line O/S

Winter 2007

Heavy LoadsOutage: 931

Temp: 25Fahrenheit

Safe operating area

Potentially safe operating area

Unsafe operating areas

Danger area: blind spot

N-2: Echo Lk-Maple VL/Rocky Rch-ML

contingency will overloadCOVINGTN TO CRESTON CKT 1

Sensitivity of South-North Ingledow-Custer limits to PSE, SCL, and SNOH Generation

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

PSE Generation (MW)

Ing

led

ow

-Cu

ster

lim

it (

MW

)

S-N Westside Limit=2000 MWS>N SCL+SNOH Gen= 140 MWS>N SCL+SNOH Gen= 460 MWS>N SCL+SNOH Gen= 775 MWN-S Westside Limit=2850 MW"S>N SCL+SNOH Gen= 140 MWN>S SCL+SNOH Gen= 460 MWN>S SCL+SNOH Gen= 775 MWCanadian Entitlment

Building a Combined 25F Nomogram Step 6: Combine all Operating Areas

Tacoma-Covington #2 230kV line O/S

Winter 2007

Heavy LoadsOutage: 931

Temp: 25Fahrenheit

Safe operating area

Potentially safe operating area

Unsafe operating areas

Danger area: blind spot