Exhibit 4(b) 

**SECOND SUPPLEMENTAL INDENTURE**

Second Supplemental Indenture (this “SupplementalIndenture”), dated as of August 3, 2009, among Texas Competitive Electric Holdings Company LLC, a Delaware limited liability company, and TCEH Finance, Inc., a Delaware corporation (collectively, the “Issuer”), theGuarantors named on the signature pages hereto (the “Guarantors”) and The Bank of New York Mellon, as Trustee (the “Trustee”). 

**W I T N E S S E T H**

WHEREAS, each of the Issuer and the Guarantors has heretofore executed anddelivered to the Trustee an Indenture, dated as of October 31, 2007, as supplemented by the Supplemental Indenture, dated as of December 6, 2007 (collectively, the “Indenture”), providing for the issuance of 10.25% SeniorNotes due 2015 (the “Senior Cash Pay Notes”), 10.25% Senior Notes due 2015, Series B (the “Senior Cash Pay Notes, Series B”) and 10.50%/11.25% Senior Toggle Notes due 2016 (together with any increases in theaggregate principal amount thereof, or any Related PIK Notes with respect thereto, in each case in connection with any PIK Payment with respect thereto, and together with the Senior Cash Pay Notes and the Senior Cash Pay Notes, Series B, the“Senior Notes”); 

WHEREAS, Section 9.01(11) of the Indenture provides that the Issuer, the Guarantors and the Trusteemay amend or supplement the Indenture, at any time after the Issue Date, without the consent of any Holder to conform the text of the Indenture to any provision of the “Description of the Notes” section of the Offering Memorandum to theextent such provision in such “Description of the Notes” section was intended to be a verbatim recitation of a provision of the Indenture; 

WHEREAS, all conditions necessary to authorize the execution and delivery of this Supplemental Indenture and to make this Supplemental Indenture valid and binding have been complied with or have been done orperformed; and 

WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is authorized to execute and deliver this SupplementalIndenture. 

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is herebyacknowledged, the parties mutually covenant and agree for the equal and ratable benefit of the Holders of the Senior Notes as follows: 

1.CAPITALIZED TERMS. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture. 

2. AMENDMENTTOTHE INDENTURE. Section 9.02 of the Indenture is amended by deleting the text of clause (2) in its entirety and inserting in lieuthereof the following text: 

“(2) reduce the principal of or change the fixed final maturity of any such Senior Note or alter or waivethe provisions with respect to the redemption of such Senior Notes (other than provisions relating to Section 3.09, Section 4.10 and Section 4.14 hereof);”. 

3. GOVERNING LAW. THIS SUPPLEMENTAL INDENTURE WILL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THELAWS OF THE STATE OF NEW YORK. 

4. FULL FORCEAND EFFECT. Except as expresslyamended hereby, the Indenture is in all respects ratified and confirmed and all the terms, conditions and provisions thereof shall remain in full force and effect. Upon the execution and delivery of this Supplemental Indenture by the Issuer, theGuarantors and the Trustee, this Supplemental Indenture shall form a part of the Indenture for all purposes, and the Issuer, the Guarantors, the Trustee and every Holder of Senior Notes heretofore or hereafter authenticated and delivered shall bebound hereby. Any and all references to the Indenture, whether within the Indenture or in any notice, certificate or other instrument or document, shall be deemed to include a reference to this Supplemental Indenture (whether or not made), unlessthe context shall otherwise require. 

5. INDENTURE REMAINSIN FULLFORCEAND EFFECT. Except as supplemented or amended hereby, all provisions in the Indenture shall remain in full force and effect. 

6. INDENTUREAND SUPPLEMENTAL INDENTURE CONSTRUED TOGETHER.This Supplemental Indenture is an indenture supplemental to the Indenture, and the Indenture and this Supplemental Indenture shall henceforth be read and construed together. 

7. CONFIRMATIONAND PRESERVATIONOF INDENTURE. The Indenture as supplementedor amended by this Supplemental Indenture is in all respects confirmed and preserved. 

8. BENEFITSOFSUPPLEMENTAL INDENTURE. Nothing in this Supplemental Indenture, express or implied, shall give to any Person other than the parties hereto and thereto and their successors hereunder and thereunder and the Holders of theSenior Notes, any benefit of any legal or equitable right, remedy or claim under the Indenture, this Supplemental Indenture or the Senior Notes. 

9. SUCCESSORS. All agreements of the Issuer and the Guarantors in this Supplemental Indenture shall bind their respective successors. All agreements of the Trustee in this Supplemental Indenture shall bind its successors.

10. THE TRUSTEE. The Trustee shall not be responsible in any manner for or in respect of the validity orsufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which are made by the Issuer and the Guarantors. 

11. COUNTERPARTS. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement. 

 

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12. EFFECTOF HEADINGS. The Section headings herein are forconvenience only and shall not affect the construction hereof. 

13. SEVERABILITY. If any provision in this SupplementalIndenture shall be invalid, illegal or unenforceable, the validity, legality or enforceability of the remaining provisions of this Supplemental Indenture or the Indenture shall not in any way be affected or impaired thereby. 

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed andattested, all as of the date first above written. 

 
**TEXAS COMPETITIVE ELECTRIC HOLDINGS COMPANY LLC**By: /s/ PAUL M. KEGLEVIC Name: Paul M. Keglevic Title: Executive Vice President and CFO
 
**TCEH FINANCE, INC.**By: /s/ PAUL M. KEGLEVIC Name: Paul M. Keglevic Title: Executive Vice President and CFO
 
**THE BANK OF NEW YORK MELLON,**as Trustee****By: /s/ L. J. O’BRIEN Name: Laurence J. O’Brien Title: Vice President
 

 
**BIG BROWN 3 POWER COMPANY LLC****BIG BROWN LIGNITE COMPANY LLC****BIG BROWN POWER COMPANY LLC****COLLIN POWER COMPANY LLC****DECORDOVA POWER COMPANY LLC****DFW MIDSTREAM SERVICES LLC****ENERGY FUTURE COMPETITIVE HOLDINGS COMPANY****GENERATION MT COMPANY LLC****GENERATION SVC COMPANY****LAKE CREEK 3 POWER COMPANY LLC****LUMINANT BIG BROWN MINING COMPANY LLC****LUMINANT ENERGY COMPANY LLC****LUMINANT ENERGY SERVICES COMPANY****LUMINANT GENERATION COMPANY LLC****LUMINANT HOLDING COMPANY LLC****LUMINANT MINERAL DEVELOPMENT COMPANY LLC**
 

[Signature Page to Second Supplemental Indenture] 

**LUMINANT ENERGY TRADING CALIFORNIA COMPANY****LUMINANT ET SERVICES COMPANY****LUMINANT MINING COMPANY LLC****LUMINANT MINING SERVICES COMPANY****LUMINANT POWER SERVICES COMPANY****LUMINANT RENEWABLES COMPANY LLC****MARTIN LAKE 4 POWER COMPANY LLC****MONTICELLO 4 POWER COMPANY LLC****MORGAN CREEK 7 POWER COMPANY LLC****NCA RESOURCES DEVELOPMENT COMPANY LLC****OAK GROVE MANAGEMENT COMPANY LLC****OAK GROVE MINING COMPANY LLC****OAK GROVE POWER COMPANY LLC****SANDOW POWER COMPANY LLC****TRADINGHOUSE 3 & 4 POWER COMPANY LLC****TRADINGHOUSE POWER COMPANY LLC****TXU CHILLED WATER SOLUTIONS**