Goshen Area Bus Reconfiguration. Presented by PacifiCorp Grid Operations. 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 - PowerPoint PPT Presentation
Goshen Area Bus Reconfiguration Presented by PacifiCorp Grid Operations Jefferson A ntelope G oshen B ig G rassy A m ps R eno LostR iver W est R exburg 115 kV R ound Valley n.o. To A naconda via P eterson Flat Tap (IP C ) To Dillon R uby Bernice W olverine C reek Jolly H ills Palisades Arco Kinport(IPC ) Borah (IPC ) Fishcreek G race Populus Sunbeam To Bridger To M idpoint Future 115 kV BPA 161 kV Path C American Falls (IPC ) To Ben Lom ond/ Terminal To W heelon Malad Mudlake Dubois Blackfoot (IPC ) Spar C anyon Threem ile Knoll S oda Sw an Valley Drum m ond Idaho Falls Targhee IPC Scoville (IN L) Treasureton Brady (IPC ) 69 kV 46 kV 345 kV 230 kV Foreign O w ned 138 kV 161 kV Rigby R exburg SugarC ity BPA BPA BPA
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
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
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
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
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
