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Goshen Area Bus Reconfiguration
Presented by PacifiCorp Grid Operations
Jefferson
Antelope
Goshen
Big Grassy
Amps
Reno
Lost River
West Rexburg
115 kV
Round Valley n.o.
To Anaconda via Peterson Flat Tap (IPC) To Dillon
RubyBernice
Wolverine Creek
Jolly Hills
Palisades
Arco
Kinport (IPC)
Borah (IPC)
Fishcreek
Grace
Populus
Sunbeam
To Bridger
To Midpoint
Future 115 kV BPA
161 kV
Path C
American Falls (IPC)
To Ben Lomond/Terminal
To Wheelon
Malad
Mudlake
Dubois
Blackfoot (IPC)
Spar Canyon
Threemile Knoll
Soda
Swan Valley
Drummond
Idaho Falls
Targhee
IPC
Scoville (INL)
Treasureton
Brady (IPC)
69 kV46 kV
345 kV230 kV
Foreign Owned
138 kV161 kV
Rigby
RexburgSugar City
BPA
BPA
BPA
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Pre-Contingency Load Shed Event
– December 4, 2013 Pre-contingency load shed required to prevent post-
contingency violation on underlying 161 kV system for loss of 345 kV source into Goshen
– Since event, PacifiCorp has taken steps to prevent another pre-contingency load shed event.
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Why was load shed required?
– NERC standard FAC-011-2 R2.1 Highest available facility rating cannot be exceeded for a
credible outage at any time.
– Peak RC enforcing these standards, via Peak RC SOL Methodology
– To prevent NERC standards violation, amount of load in the Goshen area reduced to level where 161 kV system could serve remaining load, and stay within all facility ratings following contingency
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– Example from Peak RC
Emergency
Rating
4 Hour Rating
Normal Rating
Why was load shed required?
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Preventing future load shed
– Short Term Solutions: Reconfiguring Goshen 345 kV bus (Completed) Procedure to serve Goshen area load radial off 345 kV source
(Completed) Additional relay settings on 161 kV system (Completed) Splitting Goshen 161 kV bus to prevent complete loss of load
(Completed)
– Long Term Solutions: Local Area Protection Scheme (Under study)
– Additional Transmission Capacity under study
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Reconfiguring the Goshen 345 kV bus
– Goshen 345 kV bus had a weakness If one breaker out of service, single contingency could
disconnect 345 kV source from 161 kV source• December 4: Goshen CB 303 was out of service for critical
maintenance
– Extensive engineering work performed to reconfigure the Goshen 345 kV bus, minimize risk to load
– Bus reconfigured: single breaker outage cannot remove both 345 kV sources
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Radial load procedure
– Procedure calls for opening up 161 kV ties into Goshen 161 kV bus 3 operated by PacifiCorp, 1 by Idaho Power
– If 345 kV bus is lost, all load served out of Goshen lost– Prevents pre-contingency load shedding– Not automatic– Trips all load in the area once a threshold has been exceeded
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161 kV relaying
– In coordination with Idaho Power and Northwestern Energy, relay settings placed on 161 kV ties into Goshen area to protect 161 kV lines
– Relay settings open breakers if the elements are overloaded– Prevents pre-contingency load shed – Load can survive certain outage conditions versus radial
procedure– Automatic protection: load only lost if contingency occurs– Still trips all load in the area once threshold exceeded, if
contingency occurs
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Goshen 161 kV bus split
– Solution serves portion of the Goshen area load off east bus, leaves 161 kV ties, generation, some load on west bus
– Each bus has own 345 kV transformer source– If one (or both) sources lost
West bus served off the 161 kV ties East bus is lost
– Prevents total loss of Goshen area load
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Risk to load
– Without bus reconfiguration, 100% of load served in the Goshen area at risk for an N-1-1
– Preserves as much load as possible given current transmission system
– Next two slides show amount of load at Goshen at risk for radial and split bus configuration
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Sectionalizing benefits
– Palisades loop and wind generation remain online– Facilitates faster restoration– Unilateral implementation– Does not require complex relay logic
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Load risk probability
– Now, 4 conditions need to occur simultaneously for load loss at Goshen Peak loading conditions Minimal generation Single 345 kV line out of service (maintenance, permanent fault) Additional 345 kV line suffering a permanent fault
– 1-2 can occur at same time, third is rare– Prior to PacifiCorp’s actions, only 3 of these need to occur to
trigger action (pre-contingency load shed)
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Local area protection scheme
– Local Area Protection Scheme (LAPS) potential– Will require redundancy and WECC RASRS
approval– Based on real-time system and loading conditions– LAPS could determine required amount of load to
shed for each system condition– An appropriate amount of load selected for loss of
345 kV source
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Additional system reinforcements
– 161 kV transmission capacity reinforcement Goshen-Sugarmill line scheduled to be re-conductored in
November 2014
– Additional 161 kV reinforcements under study
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Questions
Jefferson
Antelope
Goshen
Big Grassy
Amps
Reno
Lost River
West Rexburg
115 kV
Round Valley n.o.
To Anaconda via Peterson Flat Tap (IPC) To Dillon
RubyBernice
Wolverine Creek
Jolly Hills
Palisades
Arco
Kinport (IPC)
Borah (IPC)
Fishcreek
Grace
Populus
Sunbeam
To Bridger
To Midpoint
Future 115 kV BPA
161 kV
Path C
American Falls (IPC)
To Ben Lomond/Terminal
To Wheelon
Malad
Mudlake
Dubois
Blackfoot (IPC)
Spar Canyon
Threemile Knoll
Soda
Swan Valley
Drummond
Idaho Falls
Targhee
IPC
Scoville (INL)
Treasureton
Brady (IPC)
69 kV46 kV
345 kV230 kV
Foreign Owned
138 kV161 kV
Rigby
RexburgSugar City
BPA
BPA
BPA