Presentation on theme: "Goshen Area Bus Reconfiguration"— Presentation transcript:
1 Goshen Area Bus Reconfiguration Presented by PacifiCorp Grid Operations
2 Pre-Contingency Load Shed Event December 4, 2013Pre-contingency load shed required to prevent post-contingency violation on underlying 161 kV system for loss of 345 kV source into GoshenSince event, PacifiCorp has taken steps to prevent another pre-contingency load shed event.
3 Why was load shed required? NERC standard FAC R2.1Highest available facility rating cannot be exceeded for a credible outage at any time.Peak RC enforcing these standards, via Peak RC SOL MethodologyTo 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
4 Why was load shed required? Example from Peak RCEmergencyRating4 Hour RatingNormal Rating
5 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
6 Reconfiguring the Goshen 345 kV bus Goshen 345 kV bus had a weaknessIf one breaker out of service, single contingency could disconnect 345 kV source from 161 kV sourceDecember 4: Goshen CB 303 was out of service for critical maintenanceExtensive engineering work performed to reconfigure the Goshen 345 kV bus, minimize risk to loadBus reconfigured: single breaker outage cannot remove both 345 kV sources
7 Radial load procedureProcedure calls for opening up 161 kV ties into Goshen 161 kV bus3 operated by PacifiCorp, 1 by Idaho PowerIf 345 kV bus is lost, all load served out of Goshen lostPrevents pre-contingency load sheddingNot automaticTrips all load in the area once a threshold has been exceeded
8 161 kV relayingIn coordination with Idaho Power and Northwestern Energy, relay settings placed on 161 kV ties into Goshen area to protect 161 kV linesRelay settings open breakers if the elements are overloadedPrevents pre-contingency load shedLoad can survive certain outage conditions versus radial procedureAutomatic protection: load only lost if contingency occursStill trips all load in the area once threshold exceeded, if contingency occurs
9 Each bus has own 345 kV transformer source Goshen 161 kV bus splitSolution serves portion of the Goshen area load off east bus, leaves 161 kV ties, generation, some load on west busEach bus has own 345 kV transformer sourceIf one (or both) sources lostWest bus served off the 161 kV tiesEast bus is lostPrevents total loss of Goshen area load
12 Risk to loadWithout bus reconfiguration, 100% of load served in the Goshen area at risk for an N-1-1Preserves as much load as possible given current transmission systemNext two slides show amount of load at Goshen at risk for radial and split bus configuration
15 Sectionalizing benefits Palisades loop and wind generation remain onlineFacilitates faster restorationUnilateral implementationDoes not require complex relay logic
16 Load risk probabilityNow, 4 conditions need to occur simultaneously for load loss at GoshenPeak loading conditionsMinimal generationSingle 345 kV line out of service (maintenance, permanent fault)Additional 345 kV line suffering a permanent fault1-2 can occur at same time, third is rarePrior to PacifiCorp’s actions, only 3 of these need to occur to trigger action (pre-contingency load shed)
17 Local area protection scheme Local Area Protection Scheme (LAPS) potentialWill require redundancy and WECC RASRS approvalBased on real-time system and loading conditionsLAPS could determine required amount of load to shed for each system conditionAn appropriate amount of load selected for loss of 345 kV source
18 Additional system reinforcements 161 kV transmission capacity reinforcementGoshen-Sugarmill line scheduled to be re-conductored in November 2014Additional 161 kV reinforcements under study
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