Borah Mitigators Remedial Action Scheme for the Borah West Path Sponsored by: IDAHO POWER

1. Borah MitigatorsRemedial Action Scheme for the Borah West PathSponsored by: IDAHO POWER Team Members: Kyle Jones Mark Magee Jason Rippee

2. Project Background • Idaho Power wants to add to a remedial action scheme for the Borah West Path, located in Southern Idaho. This revised scheme is to include the impact of ambient temperature changes to the system (to increase the ampacity of the lines). Re-vamp the mitigation scheme of the system based on an increase in transmission current for ambient temperatures below nominal.

3. Deliverables • Simulation of the modified scheme in Power World 11 • Provide a set of options for mitigation to the customer that provide an increase in load capacity/transmission capability. • Maximize power transfer across Southern Idaho for all conditions (ie. lines faulted or lines outages)

4. Insights to the Problem • The first slide demonstrates the current limit conditions used on the Borah West Path. • The second slide gives a flow chart of what remedial action is to be taken for the limits exceeded. • The third slide shows the remedial action to be taken for each set of Borah West and Midpoint East transfer levels.

5. Calculated Borah West limits Midpoint East flow, MW (pre-disturbance) ( Summer time - 2005) W/ 1 unit trip = A = 1929 - 6.64*degC + 0.45 * 1st unit MW where Ta = actual ambient temperature in deg C 1st Bridger Unit to trip (MW) W/ 1 unit trip &bypass both series caps = Ac = 1293 -3.93*degC + 0.2384 * 1st unit MW + 0.484 * Midpoint East flow (MW) 2nd Bridger Unit to trip (MW) W/ 1 unit trip &bypass 1 series cap = AC/2 = A + (Ac-A)/2 W/ 2 unit trips = B = 1929 – 6.64*degC + 0.45 * (1st + 2nd unit MW) W 2 unit trip & bypass both series caps = Bc = 1293 – 3.93*degC + 0.2384 * (1st + 2nd unit MW) +0.484*Midpoint East flow (MW) W/ 2 unit trip &bypass 1 series cap = BC/2 = B + (Bc-B)/2

6. Midpoint East scheme will trip 1 Bridger Unit Bypass Burns Series Capacitor Critical Outage has occurred: Kinport – Midpoint and Borah – Adelaide – Midpoint #1 or #2 345kV lines Is AC/ 2 > A ? Is BW > ~1100MW Is BW > A yes yes yes no no no Is BW > A yes No action taken X33 No action taken No action taken no No action taken Trip 2nd Unit @ Bridger Bypass Midpoint Series Capacitor Initiate Bridger Redispatch or / and load curtailment to eliminate overloads on remaining Borah – Adelaide – Midpoint 345kV line and AMFLS – Adelaide and AMFLS – Plst Valley 138kV lines X33 Is BW > AC/ 2 Is BW > AC Is BW > BC yes yes yes no no no No action taken No action taken No action taken

8. Needs Analysis • The Borah West Path has some of its elements reach their thermal limit following the loss of critical transmission lines. Compensating for thermal effects will increase the load carrying capacity in lines and may avoid dropping loads during peak demand. • Provide a mitigation scheme for the case of N-1 and N-2 conditions, which means we need to mitigate single line and double line losses.

9. Constraints • Keep voltage deviation after one line loss below 5% of the normal operating voltage, and below 10% for a two line loss. • Under normal conditions conductor temperatures should not exceed 80 degrees Celsius. • Outage conditions should not exceed 90 degrees Celsius for more than 15 minutes. • In order of importance: 1) Avoid tripping Generators at all cost! ( lots of money) 2) Avoid dropping loads. 3) Avoid shorting series capacitors (not that big of deal). • Utilize thermal capabilities if possible.

10. Project Learning • Learn how thermal limits are related to the ampacity of the lines using IEEE standard publication 738-1993. • The ratio of the new ampacity to the old ampacity is proportional to the sqrt(new temp rise/ old temp rise)

11. Questions?