Oct 14, 2011

RPG Meeting

Cross Valley Brownsville Loop Project – Status report

2 Oct. 14, 2011 RPG Meeting

Project Options

Option 1 – (Sharyland and BPUB proposal)

• New 345kV Loma Alta station with two (2) 345/138kV 450 MVA auto

• ~14 mile 345kV transmission line from existing 345kV La Palma station to new 345kV Loma Alta station

• ~59 mile 345kV transmission line from new 345kV Loma Alta station to new 345kV Frontera station across the valley

Option 3

• New 345kV Loma Alta station with one 345/138kV auto

• ~25 mile 345kV transmission line from existing 345kV RioHondo station to new 345kV Loma Alta station

• Rebuild LaPalma-Cavazos-Military Highway with 2-795 ACSR

• Rebuild LaPalma-Los Fresnos-LomaAlta with 2-795 ACSR

3 Oct. 14, 2011 RPG Meeting

Project Options (Cont.)

Option 4

• New 345kV Loma Alta station with one 345/138kV auto

• ~25 mile 345kV transmission line from existing 345kV RioHondo station to new 345kV Loma Alta station

• Rebuild and convert LaPalma to Brownsville 69 kV line to a 138 kV line; Add new 138 kV substation to tie LaPalma- Brownsville and the Military Highway-Carbide138 kV lines.

Option 5 (new)

• New 345kV Loma Alta station with one 345/138kV auto

• ~25 mile 345kV transmission line from existing 345kV RioHondo station to new 345kV Loma Alta station

• ~12 mile 138kV transmission line from LaPalma – Palo Alto

4 Oct. 14, 2011 RPG Meeting

LRGV/Brownsville Area Transmission system

Rio Hondo-Loma Alta 345 kV for Options 3, 4 & 5

LaPalma 138 kV rebuild’s Option 3

LaPalma 69 kV to 138 kV Option 4

LaPalma- Palo Alto 138 kV Option 5

5 Oct. 14, 2011 RPG Meeting

Base Case Model & Assumptions

• 2016 5YTP summer peak case based on the 2011 SSWG Dataset B

• Brownsville Area Load ~ 589 MW (including 250 MW load at Loma Alta)

• Silas Ray largest combined cycle unit (train) turned off

• Silas Ray oldest unit (49 years) turned off

• Total generation online in Brownsville ~ 48 MW

• AEPSC LRGV Project

o A new 163 mile, single circuit 345kV line from Laredo Lobo to Rio Bravo to N. Edinburg

o Reconductor the existing two 345 kV line in to the LRGV

6 Oct. 14, 2011 RPG Meeting

2016 Power Flow Results N-1 & G-1 (with the new 250 MW load)

• Base Case thermal (n-0) violations in 2016

Rio Hondo – East Rio Hondo 138 kV line (151.6%)East Rio Hondo – Central Avenue Sub 138 kV line (140.4%)LaPalma – Los Fresnos 138 kV line (124.6%)LaPalma – Cavazos line 138 kV (115.3%) Loma Alta – Los Fresnos 138 kV line ( 109.1%)Military Highway – Cavazos 138 kV line (108.3%)

There are additional overloads under contingency

• No low voltage violation (in base case or under contingency)

7 Oct. 14, 2011 RPG Meeting

2016 Power Flow Results N-1 & G-1 (without the new 250 MW load)

• Base Case thermal (n-0) violations in 2016

Rio Hondo – East Rio Hondo 138 kV line (108.9%)

There are additional overloads under contingency (as shown in the map)

• No low voltage violation (in base case or under contingency)

8 Oct. 14, 2011 RPG Meeting

2016 Power Flow Results N-1-1 (without the new 250 MW load)

Prior Outage of either the Ajo-Rio Hondo 345 kV or Rio Hondo-N. Edinburg 345 KV:

The loss of the next 345 kV @ Rio Hondo would cause severe overloads on several 138 kV and 69 kV lines (cross valley lines serving Brownsville area).

Some of the major post-contingency (> 120%) N-1-1 overloads:Weslaco Unit to Steward Road 138 kV line (158.4 %)Weslaco Switching Station to Weslaco 138 kV line (149.7%)Aderhold to HEC Energy Center 138 kV line (142.7%)Heidelberg to Weslaco 138 kV line (134.0%)Elsa to Aderhold 138 kV line (133.6%)Burns to Heidelberg 138 kV line (126.3%)South McAllen to Las Milpas 138 kV line (124.5%)Wesmer to Weslaco Unit 138 kV line (120.7%)

Mitigation plan to prepare for this next contingency (under system peak conditions) would require load shed in the East Valley/Brownsville area.

Based on this study, it is estimated that under the 2016 system peak system conditions, it would require ~ 430 MW of load shed in the East Valley/Brownsville area to relieve all N-1-1 overloads.

9 Oct. 14, 2011 RPG Meeting

Summary of Results

√ - no criteria violation x – criteria violation

Options Project Description

N-1+G-1 Criteria N-1-1 Criteria

without 250 MW load with 250 MW load without 250 MW load with 250 MW load

1 LaPlama - Loma Alta 345 kV & Frontera - Loma Alta 345 kV √ √ x x

1a LaPlama - Loma Alta 345 kV √ x x x1b Frontera - Loma Alta 345 kV √ x x x

3RioHondo - Loma Alta 345 kV, Rebuild LaPalma-Cavazos-Military Highway & Rebuild LaPalma-Los Fresnos-LomaAlta √ √ x x

3a RioHondo - Loma Alta 345 kV √ x x x

3b Rebuild LaPalma-Cavazos-Military Highway √ x x x

3c Rebuild LaPalma-Los Fresnos-LomaAlta √ x x x

4RioHondo - Loma Alta 345 kV, Rebuild and convert LaPalma-Brown 69 kV to 138 kV √ √ x x

4a RioHondo - Loma Alta 345 kV √ x x x

4b Rebuild and conver LaPalma-Brown 69 kV to 138 kV √ x x x

5 RioHondo - Loma Alta 345 kV, LaPalma-Palo Alto 138 kV √ √ x x

5a RioHondo - Loma Alta 345 kV √ x x x5b LaPalma-Palo Alto 138 kV √ x x x

10 Oct. 14, 2011 RPG Meeting

Project Options for N-1-1 Criteria

Loma Alta-N. Edinburg 345 kV instead of the Loma Alta-Rio Hondo 345 kV for Options 3, 4 & 5

11 Oct. 14, 2011 RPG Meeting

Study status/update

• Completed the studies for the N-1+G-1, N-1-1 and new 250 MW load sensitivities.

• Working with TO’s to obtain cost estimates for the options.

• Working on completing the draft study report.

• The tentative date for the study report is end of October or first week of November.

12 September 17, 2010 RPG Meeting March 12, 2010

Questions?