Barrilla Junction Area Transmission Improvements Project ERCOT Regional Planning Group March 22nd. 2016 (Prepared by AEPSC)

One line of the existing Barrilla Junction Area transmission system with future loads

Study Drivers New Direct interconnection load requests and increased load forecast at existing points of delivery Increased solar generation interconnections in the area Maintain NERC, ERCOT, Oncor and AEP reliability criteria Bus Name Bus Number 2016 2017 2018 2019 2020 Pig Creek 38375 25.00 County Road 101 6657 24.60 34.30 36.80 37.40 Gas Pad 11112 21.90 Musquiz 38305 15.38 27.50 28.90 34.20 34.10 Lotebush 6656 0.00 5.75 23.33 23.41 Hackberry Draw 38370 6.64  Total   86.88 114.45 133.43 141.31 141.81

Study Methodology Case preparation West Texas Study 2020 case modified with the latest load projections from customer requests Dispatch assumption given flows on the north and east of Barrilla Junction are heavily impacted by the generation at Permian Basin, Barrilla Junction and Ft. Stockton Study zone comprised of the West and Far West zones Branch loading and bus voltages monitored for 69 kV and above facilities Contingency events Contingency Event NERC Event Description N-0 P0 System normal, Zero elements out of service. N-1 P1 Forced outage of a single Transmission line, Transformer, Generating unit, Common tower outage, Shunt or FACTS device. N-G-1 P3 Loss of a generating unit followed by an N-1 event defined above.

Study Methodology Generation Dispatch Assumptions In the Low Wind (LW) dispatch, all the area wind generators were dispatched at 20% with the exception of the two Woodward units that were dispatched to 0%. In the High Wind (HW) dispatch, all area wind generators including the Woodward units were dispatched at 100% of Pmax. In the Low Solar (LS) dispatch, all the solar generators in the study area were dispatched to 0%. In the High Solar (HS) dispatch, all solar generators in the study area were dispatched at 100% of Pmax. In the Low Gas (LG) dispatch, all the area gas generators were dispatched at 20% with the exception of the Permian gas units that were dispatched at 0%. In the High Gas (HG) dispatch, all the area gas generators were dispatched at 100% of Pmax.   2020 HS/LW/HG 2020 HS/HW/LG 2020 LS/LW/LG 2020 LS/LW/HG Solar 100% 0% Wind 20% Woodward Gas Permian

Existing System Performance Existing system cannot support the projected load growth in the area and the export of renewable (solar) generation outside the area Most Limiting Contingency: Loss of either end of the line System Limitation: Post Contingency Voltages in the Barrilla Junction area drop below 0.92 p.u. Overload of the existing line beyond emergency rating Reasons Why Additional Facilities Will Be Required By Jan. 2020 Load connecting to Permian Basin – Barrilla Junction line is projected to be at 150 MW Solar generation requests in the area – 1,950 MW Improvements are Required to Maintain NERC Compliance

One line of the existing Barrilla Junction Area transmission system showing overloaded facilities

AEP and Oncor Recommendation Recommended Solution: Rebuild the existing Barrilla Junction/Solstice to Permian Basin AEP-TNC/Oncor 138 kV transmission line – approximately 54 miles Hackberry Tap (Lotebush)– Build a new station near the existing tap location and install a dynamic reactive device. Ft. Stockton Plant – Rebuild existing Ft. Stockton plant to a multi bus configuration and install dynamic reactive device. Benefits: Improves Load Serving Capability of the Permian Basin – Barrilla Junction 138 kV line Relieves congestion in the Barrilla Junction Area Recommended in the 2015 RTP plan and passed the economic test Estimated Cost: $111.91 M

Rebuild Solstice to Permian Basin 138 kV Lotebush/Hackberry Tap – Add dynamic reactive device Rebuild Solstice to Permian Basin 138 kV Pig Creek Rio Pecos Barrilla Junction / Solstice Ft. Stockton Plant- Add dynamic reactive device

One line of the Barrilla Junction Area Transmission System Improvements