SUPPLEMENTAL TRUST INDENTURE

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TABLE OF CONTENTS

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Supplemental Trust Indenture, made effective as of the 1 ^st day of September, 2008, by and between NORTHERN STATES POWER COMPANY, a corporation duly organized and existing under and by virtue of the laws of the State of Wisconsin, having its principal office in the City of Eau Claire, Wisconsin (the “Company”), party of the first part, and U.S. BANK NATIONAL ASSOCIATION, a national banking association organized and existing under and by virtue of the laws of the United States of America, having its principal office in the City of St. Paul, Minnesota (as successor Trustee to Firstar Bank Milwaukee), as trustee (the “Trustee”), party of the second part;

WITNESSETH:

WHEREAS, the Company, has heretofore executed and delivered to the Trustee its Trust Indenture, made as of April 1, 1947 (the “1947 Indenture”), whereby the Company granted, bargained, sold, warranted, released, conveyed, assigned, transferred, mortgaged, pledged, set over and confirmed to the Trustee, and to its respective successors in trust, all property, real, personal and mixed then owned or thereafter acquired or to be acquired by the Company (except as therein excepted from the lien thereof) and subject to the rights reserved by the Company in and by the provisions of the 1947 Indenture, to be held by said Trustee in trust in accordance with the provisions of the 1947 Indenture for the equal pro rata benefit and security of all and every of the bonds issued and to be issued thereunder in accordance with the provisions thereof; and

WHEREAS, the Indenture (as defined below) provides that bonds may be issued thereunder in one or more series, each series to have such distinctive designation as the Board of Directors of the Company may select for such series; and

WHEREAS, the Company heretofore has executed and delivered to the Trustee the following Supplemental Trust Indentures which, in addition to conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee, and its respective successors in said trust, additional property acquired by it subsequent to the preparation of the next preceding Supplemental Trust Indenture and adding to the covenants, conditions and agreements of the Indenture certain additional covenants, conditions and agreements to be observed by the Company, created the following series of First Mortgage Bonds:

WHEREAS, the 1947 Indenture and all of the foregoing Supplemental Trust Indentures are referred to herein collectively as the “Original Indenture”; and

WHEREAS, the Company heretofore has executed and delivered to the Trustee a Supplemental and Restated Trust Indenture, dated March 1, 1991 (the “Restated Indenture”), which, in addition to conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee, and its respective successors in said trust, additional property acquired by it subsequent to the preparation of the next preceding Supplemental Trust Indenture, amended and restated the Original Indenture; and

WHEREAS, the Restated Indenture became effective and operative on October 1, 1993; and

WHEREAS, the Original Indenture, the Restated Indenture and all trust indentures supplemental thereto are referred to herein collectively as the “Indenture” and certain capitalized terms defined in Section 1.03 of the Restated Indenture are used with the same meanings herein; and

WHEREAS, the Company is desirous of providing for the creation under the Indenture of a new series of First Mortgage Bonds, said new series of bonds to be designated “First Mortgage Bonds, Series due September 1, 2038” the bonds of said series to be issued as registered bonds without coupons in denominations of a multiple of $1,000, and the bonds of said series to be substantially in the following form:

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(Form of Bonds of Series due September 1, 2038)
NORTHERN STATES POWER COMPANY
(Incorporated under the laws of the State of Wisconsin)
First Mortgage Bond
Series due September 1, 2038
CUSIP 665789 AW3

Unless this certificate is presented by an authorized representative of The Depository Trust Company, a New York corporation, to the issuer or its agent for registration of transfer, exchange or payment, and any certificate issued is registered in the name of Cede & Co. or such other name as requested by an authorized representative of The Depository Trust Company (and any payment is made to Cede & Co. or to such other entity as is requested by an authorized representative of The Depository Trust Company), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL since the registered owner hereof, Cede & Co., has an interest herein.*

EXCEPT UNDER THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, THIS GLOBAL BOND MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITORY OR BY A NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY, ANOTHER NOMINEE OF THE DEPOSITORY, A SUCCESSOR OF THE DEPOSITORY OR A NOMINEE OF SUCH SUCCESSOR. *

NORTHERN STATES POWER COMPANY, a corporation organized and existing under and by virtue of the laws of the State of Wisconsin (the “Company”), for value received, hereby promises to pay to Cede & Co. or its registered assigns, at the office of the Trustee in St. Paul, Minnesota, the sum of                    Dollars in lawful money of the United States of America, on the 1 ^st day of September 2038, and to pay interest hereon from the date hereof at the rate of 6.375 percent per annum, in like money, until the principal hereof becomes due and payable; said interest being payable to the person entitled to such interest at the office of U.S. Bank National Association in  St. Paul, Minnesota on the 1 ^st day of March and on the 1 ^st day of September in each year; provided that at the option of the Company payment of interest may be made by wire transfer to the person entitled thereto if such person has provided proper wire transfer instructions or by check mailed to the address of such person as such address shall appear in the Bond Register maintained by the Trustee; provided further that as long as there is no existing default in the payment of interest and except for the payment of defaulted interest, the interest payable on any March 1 or September 1 will be paid to the person in whose name this bond was registered at the close of business on the record date (the February 15 prior to such March 1 or August 15 prior to such September 1 whether or not a business day).  If any interest payment date or date on which the principal of this bond is required to be paid is not a business day, then payment of principal, premium or interest need not be made on such date but may be made on the next succeeding business day with the same force and effect as if made on such interest payment date or date on which the principal of this bond is required to be paid and, in the case of

* This legend to be included if the bonds are issued as a global bond in book-entry form.

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timely payment thereof, no interest shall accrue for the period from and after such interest payment date or the date on which the principal of this bond is required to be paid.  The term “business day” shall mean any day other than a Saturday or Sunday or a day on which the offices of the Trustee in the City of St. Paul, Minnesota are closed pursuant to authorization of law.

This bond is one of a duly authorized issue of bonds of the Company, known as its First Mortgage Bonds, of the series and designation indicated on the face hereof, which issue of bonds consists, or may consist, of several series of varying denominations, dates and tenor, all issued and to be issued under and equally secured (except insofar as a sinking fund, or similar fund, established in accordance with the provisions of the Indenture may afford additional security for the bonds of any specific series) by a Trust Indenture dated April 1, 1947 (the “1947 Indenture”), as supplemented by 14 supplemental trust indentures (collectively, the “Supplemental Indentures”), a Supplemental and Restated Trust Indenture dated March 1, 1991 (the “Restated Indenture”) and a new supplemental trust indenture for the bonds of this series (the “New Supplemental Indenture”), all of which instruments are herein collectively called the “Indenture,” executed by the Company to U.S. Bank National Association, as successor trustee (the “Trustee”).  The Restated Indenture amends and restates the 1947 Indenture and certain of the Supplemental Indentures and became effective and operative on October 1, 1993.  Certain capitalized terms defined in the Indenture are used with the same meanings herein.  Reference is made to the Indenture for a complete description of its terms.  Reference hereby is made to the Indenture for a description of the property mortgaged and pledged, the nature and extent of the security, the rights of the registered holders of the bonds as to such security and the terms and conditions upon which the bonds may be issued under the Indenture and are secured.  The principal hereof may be declared or may become due on the conditions, in the manner and at the time set forth in the Indenture upon the happening of a Completed Default as provided in the Indenture.

With the consent of the Company and to the extent permitted by and as provided in the Indenture, the rights and obligations of the Company and of the registered holders of the bonds and the terms and provisions of the Indenture and of any instruments supplemental thereto may be modified or altered by the affirmative vote of the registered holders of at least 66 2/3% in principal amount of the bonds then outstanding under the Indenture and any instruments supplemental thereto (excluding bonds disqualified from voting by reason of the interest of the Company or of certain related persons therein as provided in the Indenture); provided that without the consent of all registered holders of all bonds affected no such modification or alteration shall permit the extension of the maturity of the principal of any bond or the reduction in the rate of interest hereon or any other modification in the terms of payment of such principal or interest.

The Company and the Trustee may deem and treat the person in whose name this bond is registered as the absolute owner hereof for the purpose of receiving payment of or on account of the principal hereof and interest hereon and for all other purposes and shall not be affected by any notice to the contrary.

The bonds of the Series due September 1, 2038, shall be redeemable at the option of the Company as a whole or in part on any date upon not less than 30 days’ previous notice to be given in the manner and with the effect provided in Section 10.02 of the Indenture at a

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redemption price equal to the greater of (a) 100% of the principal amount being redeemed or (b) the sum of the present values of the remaining scheduled payments of principal and interest on the bonds of the Series due September 1, 2038 that are being redeemed (excluding the portion of any such interest accrued to the date fixed for redemption), discounted to the date fixed for redemption on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Yield plus 35 basis points, plus accrued and unpaid interest to the date fixed for redemption date.

“Treasury Yield” means, for any date fixed for redemption, (1) the yield, under the heading which represents the average for the immediately preceding week, appearing in the most recently published statistical release designated “H.15(519)” or any successor publication which is published weekly by the Board of Governors of the Federal Reserve System and which establishes yields on actively traded U.S. Treasury securities adjusted to constant maturity under the caption “Treasury Constant Maturities,” for the maturity corresponding to the Comparable Treasury Issue (if no maturity is within three months before or after the remaining term, yields for the two published maturities most closely corresponding to the Comparable Treasury Issue will be determined and the Treasury Yield will be interpolated or extrapolated from such yields on a straight line basis, rounding to the nearest month); or (2) if such release (or any successor release) is not published during the week preceding the calculation date or does not contain such yields, the rate per annum equal to the semiannual equivalent yield to maturity of the Comparable Treasury Issue, calculated using a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury Price for such date fixed for redemption. The Treasury Yield will be calculated on the third business day preceding the date fixed for redemption.

“Comparable Treasury Issue” means the U.S. Treasury security selected by an Independent Investment Banker as having a maturity comparable to the remaining term of the first mortgage bonds being redeemed that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of comparable maturity to the remaining term of the first mortgage bonds being redeemed.

“Comparable Treasury Price” means (1) the average of the Reference Treasury Dealer Quotations for the date fixed for redemption, after excluding the highest and lowest Reference Treasury Dealer Quotations for the date fixed for redemption, or (2) if the Trustee obtains fewer than four Reference Treasury Dealer Quotations, the average of all of the Reference Treasury Dealer Quotations.

“Independent Investment Banker” means Banc of America Securities LLC or BNY Mellon Capital Markets, LLC or their respective successors or, if such firms or successors are unwilling or unable to select the Comparable Treasury Issue, an independent investment banking institution of national standing appointed by the Trustee after consultation with us.

“Reference Treasury Dealer” means (1) each of Banc of America Securities LLC and BNY Mellon Capital Markets, LLC and any other primary U.S. Government securities dealer in the United States (a “Primary Treasury Dealer”) designated by, and not affiliated with, Banc of America Securities LLC or BNY Mellon Capital Markets, LLC or their respective successors, provided, however, that if Banc of America Securities LLC or BNY Mellon Capital Markets,

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LLC or any of their respective designees ceases to be a Primary Treasury Dealer, we will appoint another Primary Treasury Dealer as a substitute and (2) any other Primary Treasury Dealer selected by us after consultation with an Independent Investment Banker.

“Reference Treasury Dealer Quotations” means, for each Reference Treasury Dealer and any date fixed for redemption, the average, as determined by the Independent Investment Banker, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the Independent Investment Banker by the Reference Treasury Dealer at 5:00 p.m., New York City Time, on the third business day preceding the date fixed for redemption.

This bond is transferable as prescribed in the Indenture by the registered holder hereof in person, or by his duly authorized attorney, at the office of the Trustee in St. Paul, Minnesota, or elsewhere if authorized by the Company, upon surrender and cancellation of this bond, and thereupon a new bond or bonds of the same series and of a like aggregate principal amount will be issued to the transferee in exchange therefor as provided in the Indenture, upon payment of taxes or other governmental charges, if any, that may be imposed in relation thereto.

Bonds of this series are interchangeable as to denominations in the manner and upon the conditions prescribed in the Indenture.

No charge shall be made by the Company for any exchange or transfer of bonds of this series, other than for taxes or other governmental charges, if any, that may be imposed in relation thereto.

The Company shall not be required to issue, transfer or exchange any bond of this series during a period of 15 days immediately preceding any selection of bonds of this series to be redeemed.  The Company shall not be required to transfer or exchange any bond of this series called or being called for redemption in its entirety or to transfer or exchange the called portion of a bond of this series which has been called for partial redemption.

No recourse shall be had for the payment of the principal of or any premium or the interest on this bond, or any part thereof, or of any claim based hereon or in respect hereof or of said Indenture, against any incorporator, or any past, present or future shareholder, officer or director of the Company or of any predecessor or successor corporation, either directly or through the Company, or through any such predecessor or successor corporation, or through any receiver or a trustee in bankruptcy, whether by virtue of any constitution, statute or rule of law or by the enforcement of any assessment or penalty or otherwise, all such liability being, by the acceptance hereof and as part of the consideration for the issue hereof, expressly waived and released, as more fully provided in the Indenture.

This bond shall not be valid or become obligatory for any purpose unless and until the certificate of authentication hereon shall have been signed by or on behalf of U.S. Bank National Association, as successor Trustee under the Indenture, or its successor thereunder.

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IN WITNESS WHEREOF, NORTHERN STATES POWER COMPANY has caused this bond to be signed in its name by its President or a Vice President and its corporate seal, or a facsimile thereof, to be hereto affixed and attested by its Secretary or an Assistant Secretary.

(Form of Trustee’s Certificate)

This bond is one of the bonds of the series designated thereon, described in the within-mentioned Indenture.

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WHEREAS, the Company is desirous of conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee and to its respective successors in trust, additional property acquired by it subsequent to the date of the preparation of the Supplemental Trust Indenture dated as of September 1, 2003; and

WHEREAS, the Indenture provides in substance that the Company and the Trustee may enter into indentures supplemental thereto for the purposes, among others, of creating and setting forth the terms of any new series of bonds and of conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee additional property of the Company, and for any other purpose not inconsistent with the terms of the Indenture; and

WHEREAS, the execution and delivery of this Supplemental Trust Indenture have been duly authorized by a resolution adopted by the Board of Directors or an Executive Committee of the Board of Directors of the Company;

WHEREAS, the Trustee has duly determined to execute this Supplemental Trust Indenture and to be bound, insofar as it may lawfully do so, by the provisions hereof;

NOW, THEREFORE, Northern States Power Company, in consideration of the premises and of one dollar duly paid to it by the Trustee at or before the ensealing and delivery of these presents, the receipt of which is hereby acknowledged, and other good and valuable considerations, does hereby covenant and agree to and with U.S. Bank National Association, as Trustee, and its successors in the trust under the Indenture for the benefit of the registered holders of the bonds, or any of them, issued or to be issued thereunder, as follows:

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ARTICLE I
SPECIFIC SUBJECTION OF ADDITIONAL PROPERTY
TO THE LIEN OF THE INDENTURE

SECTION 1.01.  The Company, in order to better secure the payment, both of the principal and interest, of all bonds of the Company at any time outstanding under the Indenture according to their tenor and effect and the performance of and compliance with the covenants and conditions contained in the Indenture, has granted, bargained, sold, warranted, released, conveyed, assigned, transferred, mortgaged, pledged, set over and confirmed, and by these presents does grant, bargain, sell, warrant, release, convey, assign, transfer, mortgage, pledge, set over and confirm, unto U.S. Bank National Association, as Trustee, and to its respective successors in said trust forever, subject to the rights reserved by the Company in and by the provisions of the Indenture, all of the property described and mentioned or enumerated in a schedule annexed hereto and marked Schedule A, reference to said schedule being made hereby with the same force and effect as if the same were incorporated herein at length; together with all and singular the tenements, hereditaments and appurtenances belonging and in any way appertaining to the aforesaid property or any part thereof with the reversion and reversions, remainder and remainders, tolls, rents and revenues, issues, income, products and profits thereof;

Also, in order to subject the personal property and chattels of the Company to the Lien of the Indenture and in conformity with the provisions of the Uniform Commercial Code, all fossil, nuclear, hydro and other electric generating plants, including buildings and other structures, turbines, generators, boilers, reactors, nuclear fuel, other boiler plant equipment, condensing equipment and all other generating equipment; substations; electric transmission and distribution systems, including structures, poles, towers, fixtures, conduits, insulators, wires, cables, transformers, services and meters; steam heating mains and equipment; gas transmission and distribution systems, including structures, storage facilities, mains, compressor stations, purifier stations, pressure holders, governors, services and meters; office, shop and other buildings and structures, furniture and equipment; apparatus and equipment of all other kinds and descriptions; all municipal and other franchises, all leaseholds, licenses, permits, privileges and patent rights, parts or parcels of such real property; all as now owned or hereafter acquired by the Company pursuant to the provisions of the Indenture;

All the estate, right, title and interest and claim whatsoever, at law as well as in equity, that the Company now has or hereafter may acquire in and to the aforesaid property and franchises and every part and parcel thereof; excluding, however, (1) all shares of stock, bonds, notes, evidences of indebtedness and other securities other than such as may be or are required to be deposited from time to time with the Trustee in accordance with the provisions of the Indenture; (2) cash on hand and in banks other than such as may be or is required to be deposited from time to time with the Trustee in accordance with the provisions of the Indenture; (3) contracts, claims, bills and accounts receivable and choses in action other than such as may be or are required to be assigned to the Trustee in accordance with the provisions of the Indenture; (4) motor vehicles; (5) any stock of goods, wares and merchandise, equipment and supplies acquired for the purpose of sale or lease in the usual course of business or for the purpose of consumption in the operation, construction or repair of any of the properties of the Company; and (6) the properties described in Schedule B annexed to the 1947 Indenture;

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To have and to hold all said property, real, personal and mixed, mortgaged, pledged or conveyed by the Company as aforesaid, or intended so to be, to the Trustee and its successors and assigns forever, subject, however, to Permitted Encumbrances and to the further reservations, covenants, conditions, uses and trusts set forth in the Indenture; in trust nevertheless for the same purposes and upon the same conditions as are set forth in the Indenture.

ARTICLE II
FORM AND EXECUTION OF SERIES DUE SEPTEMBER 1, 2038

SECTION 2.01.  There is hereby created, for issuance under the Indenture, a series of bonds designated Series due September 1, 2038, each of which shall bear the descriptive title “First Mortgage Bond, Series due September 1, 2038” and the form thereof shall contain suitable provisions with respect to the matters specified in this Section 2.01.  The bonds of said series shall be substantially of the tenor and purport hereinbefore recited.  The bonds of said series shall initially be authenticated and delivered in the aggregate principal amount of $200,000,000.&n