<PAGE>


                                                                    EXHIBIT 4.73


                          SUPPLEMENTAL TRUST INDENTURE

                                      FROM

                          NORTHERN STATES POWER COMPANY

                                       TO

                            BNY MIDWEST TRUST COMPANY
                                     TRUSTEE

                             DATED AS OF MAY 1, 2003

                                 SUPPLEMENTAL TO

                                 TRUST INDENTURE
                             DATED FEBRUARY 1, 1937

                                       AND

                            SUPPLEMENTAL AND RESTATED
                              TRUST INDENTURE DATED
                                   MAY 1, 1988


<PAGE>

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                    Page
<S>                                                                                 <C>
ARTICLE I.......................................................................     10
     SECTION 1.01...............................................................     10
     SECTION 1.02...............................................................     11
     SECTION 1.03...............................................................     11
     SECTION 1.04...............................................................     12
     SECTION 1.05...............................................................     12
     SECTION 1.06...............................................................     12

ARTICLE II. APPOINTMENT OF AUTHENTICATING AGENT.................................     12
     SECTION 2.01...............................................................     12
     SECTION 2.02...............................................................     12
     SECTION 2.03...............................................................     13
     SECTION 2.04...............................................................     13

ARTICLE III. FINANCING STATEMENT TO COMPLY WITH THE UNIFORM COMMERCIAL CODE.....     14
     SECTION 3.01...............................................................     14
     SECTION 3.02...............................................................     14
     SECTION 3.03...............................................................     14
     SECTION 3.04...............................................................     14

ARTICLE IV. AMENDMENTS TO INDENTURE.............................................     18
     SECTION 4.01...............................................................     18

ARTICLE V. MISCELLANEOUS........................................................     18
     SECTION 5.01...............................................................     18
     SECTION 5.02...............................................................     19
     SECTION 5.03...............................................................     19
     SECTION 5.04...............................................................     19
     SECTION 5.05...............................................................     19
     SECTION 5.06...............................................................     19
</TABLE>

<PAGE>

         SUPPLEMENTAL TRUST INDENTURE, made as of the 1ST day of May, 2003, but
effective as of May 16, 2003, by and between NORTHERN STATES POWER COMPANY
(formerly Northern Power Corporation), a corporation duly organized and existing
under and by virtue of the laws of the State of Minnesota, having its principal
office in the City of Minneapolis in said State (the "Company"), party of the
first part, and BNY Midwest Trust Company, a corporation duly organized and
existing under and by virtue of the laws of the State of Illinois, having its
principal office in the City of Chicago in said State and the successor to
Harris Trust and Savings Bank, as Trustee (the "Trustee"), party of the second
part;

                              W I T N E S S E T H:

         WHEREAS, a predecessor in interest to the Company, Xcel Energy Inc.
(formerly Northern States Power Company), a corporation duly organized and
existing under and by virtue of the laws of the State of Minnesota (the
"Predecessor Company"), heretofore has executed and delivered to the Trustee its
Trust Indenture (the "1937 Indenture"), made as of February 1, 1937, whereby the
Predecessor 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
Predecessor Company (except as therein excepted from the lien thereof) and
subject to the rights reserved by the Predecessor Company in and by the
provisions of the 1937 Indenture, to be held by said Trustee in trust in
accordance with provisions of the 1937 Indenture for the equal pro rata benefit
and security of all and every of the bonds issued thereunder in accordance with
the provisions thereof; and

         WHEREAS, the Predecessor Company heretofore has executed and delivered
to the Trustee a Supplemental Trust Indenture, made as of June 1, 1942, whereby
the Predecessor Company conveyed, assigned, transferred, mortgaged, pledged, set
over, and confirmed to the Trustee, and its respective successors in said trust,
additional property acquired by it subsequent to the date of the 1937 Indenture;
and

         WHEREAS, the Predecessor Company heretofore has executed and delivered
to the Trustee the following additional 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 1937 Indenture certain additional covenants,
conditions, and agreements to be observed by the Predecessor Company, created
the following series of First Mortgage Bonds:

<TABLE>
<CAPTION>
DATE OF SUPPLEMENTAL TRUST
        INDENTURE                       DESIGNATION OF SERIES
--------------------------      -------------------------------------
<S>                             <C>
February 1, 1944                Series due February 1, 1974 (retired)
October 1, 1945                 Series due October 1, 1975 (retired)
July 1, 1948                    Series due July 1, 1978 (retired)
August 1, 1949                  Series due August 1, 1979 (retired)
June 1, 1952                    Series due June 1, 1982 (retired)
</TABLE>

<PAGE>

<TABLE>
<S>                             <C>
October 1, 1954                 Series due October 1, 1984 (retired)
September 1, 1956               Series due 1986 (retired)
August 1, 1957                  Series due August 1, 1987 (redeemed)
July 1, 1958                    Series due July 1, 1988 (retired)
December 1, 1960                Series due December 1, 1990 (retired)
August 1, 1961                  Series due August 1, 1991 (retired)
June 1, 1962                    Series due June 1, 1992 (retired)
September 1, 1963               Series due September 1, 1993 (retired)
August 1, 1966                  Series due August 1, 1996 (redeemed)
June 1, 1967                    Series due June 1, 1995 (redeemed)
October 1, 1967                 Series due October 1, 1997 (redeemed)
May 1, 1968                     Series due May 1, 1998 (redeemed)
October 1, 1969                 Series due October 1, 1999 (redeemed)
February 1, 1971                Series due March 1, 2001 (redeemed)
May 1, 1971                     Series due June 1, 2001 (redeemed)
February 1, 1972                Series due March 1, 2002 (redeemed)
January 1, 1973                 Series due February 1, 2003 (redeemed)
January 1, 1974                 Series due January 1, 2004 (redeemed)
September 1, 1974               Pollution Control Series A (redeemed)
April 1, 1975                   Pollution Control Series B (redeemed)
May 1, 1975                     Series due May 1, 2005 (redeemed)
March 1, 1976                   Pollution Control Series C (retired)
June 1, 1981                    Pollution Control Series D, E and F (redeemed)
December 1, 1981                Series due December 1, 2011 (redeemed)
May 1, 1983                     Series due May 1, 2013 (redeemed)
December 1, 1983                Pollution Control Series G (redeemed)
September 1, 1984               Pollution Control Series H (redeemed)
December 1, 1984                Resource Recovery Series I (redeemed)
May 1, 1985                     Series due June 1, 2015 (redeemed)
September 1, 1985               Pollution Control Series J, K and L
July 1, 1989                    Series due July 1, 2019 (redeemed)
June 1, 1990                    Series due June 1, 2020 (redeemed)
October 1, 1992                 Series due October 1, 1997 (retired)
April 1, 1993                   Series due April 1, 2003 (retired)
December 1, 1993                Series due December 1, 2000 (retired), and
                                December 1, 2005
February 1, 1994                Series due February 1, 1999 (retired)
October 1, 1994                 Series due October 1, 2001 (retired)
June 1, 1995                    Series due July 1, 2025
April 1, 1997                   Pollution Control Series M (redeemed), N, O and P
March 1, 1998                   Series due March 1, 2003 (retired) and March 1, 2028
May 1, 1999                     Resource Recovery Series Q
June 1, 2000                    Resource Recovery Series R; and
</TABLE>

                                       2
<PAGE>

         WHEREAS, on August 18, 2000 New Centuries Energies, Inc. was merged
with and into the Predecessor Company and the Predecessor Company changed its
corporate name from Northern States Power Company to Xcel Energy Inc.; and

         WHEREAS, pursuant to an Assignment and Assumption Agreement dated as of
August 18, 2000 between the Predecessor Company and the Company, substantially
all the assets of the Predecessor Company (other than the stock of the
Predecessor Company's subsidiaries) were conveyed to, and substantially all the
liabilities of the Predecessor Company, including liabilities created under the
Indenture, were assumed by, the Company (the "Assignment"); and

         WHEREAS, pursuant to the Supplemental Trust Indenture dated as of
August 1, 2000 among the Predecessor Company, the Company and Harris Trust and
Savings Bank, as Trustee, the requirements and conditions precedent set forth in
the Original Indenture and the Restated Indenture (each as hereinafter defined)
with respect to the Assignment were satisfied; and

         WHEREAS, the Company heretofore has executed and delivered to the
Trustee the following additional 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 (or, as the case may be, the
Predecessor Company) subsequent to the preparation of the next preceding
Supplemental Trust Indenture and adding to the covenants, conditions, and
agreements of the 1937 Indenture certain additional covenants, conditions, and
agreements to be observed by the Company, created the following series of First
Mortgage Bonds:

<TABLE>
<CAPTION>
DATE OF SUPPLEMENTAL TRUST
        INDENTURE                           DESIGNATION OF SERIES
--------------------------      ---------------------------------------------
<S>                             <C>
June 1, 2002                    Series due August 15, 2003
July 1, 2002                    Pollution Control Series S
August 1, 2002                  Series A and Series B due August 28, 2012; and
</TABLE>

         WHEREAS, the 1937 Indenture and all of the foregoing Supplemental Trust
Indentures are referred to herein collectively as the "Original Indenture;" and

         WHEREAS, the Predecessor Company heretofore has executed and delivered
to the Trustee a Supplemental and Restated Trust Indenture, dated May 1, 1988
(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 will not become effective and operative
until all bonds of each series issued under the Original Indenture prior to May
1, 1988 shall have been retired through payment or redemption (including those
bonds "deemed to be paid" within the meaning of that term as used in Article
XVII of the 1937 Indenture) or until, subject to certain exceptions, the holders
of the requisite principal amount of such bonds shall have consented to

                                       3
<PAGE>

the amendments contained in the Restated Indenture (such date being herein
called the "Effective Date"); and

         WHEREAS, the Original Indenture and the Restated Indenture are referred
to herein collectively as the "Indenture"; and

         WHEREAS, pursuant to the Agreement of Resignation, Appointment and
Acceptance dated as of May 1, 2002 among the Company, BNY Midwest Trust Company,
as successor trustee, and Harris Trust and Savings Bank, the Trustee accepted
the rights, powers, duties and obligations of the trustee under the Indenture
effective as of May 9, 2002; and

         WHEREAS, the Indenture 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 is entering into a Credit Agreement dated as of
May 16, 2003 (the "Credit Agreement") among the Company, Wells Fargo Bank, N.A.,
as Administrative Agent (the "Administrative Agent") and the other banks party
thereto (collectively, the "Banks") pursuant to which the Company can borrow and
obtain letters of credit up to an aggregate of $275,000,000 at any one time
outstanding; and

         WHEREAS, in order to secure the Company's Obligations under and as
defined in the Credit Agreement, the Company desires to provide for the issuance
under the Indenture to the Administrative Agent, for the benefit of itself and
the other Banks, of a new series of bonds to be designated "First Mortgage
Bonds, Series due 2004, extendible through 2006 (the "Bonds"); and

         WHEREAS, the Bonds to be issued as registered bonds without coupons in
denominations of a multiple of $1000, and the bonds of said series to be
substantially in the form and of the tenor following, to-wit:

                                 (Form of Bonds)
                          NORTHERN STATES POWER COMPANY
             (Incorporated under the laws of the State of Minnesota)
                               First Mortgage Bond
                    Series due 2004, extendible through 2006

No. _________                                                        $__________

         THIS BOND HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, AND MAY BE OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED ONLY IN
COMPLIANCE WITH APPLICABLE SECURITIES LAWS.

         PURSUANT TO A SECURITY AGREEMENT (THE "SECURITY AGREEMENT") DATED MAY
16, 2003 BETWEEN THE COMPANY (AS DEFINED BELOW) AND THE ADMINISTRATIVE AGENT (AS
DEFINED BELOW), THIS BOND AND ALL PROCEEDS THEREOF HAVE BEEN PLEDGED TO SECURE
CERTAIN OBLIGATIONS OF THE

                                       4
<PAGE>

COMPANY. THE SECURITY AGREEMENT SETS FORTH VARIOUS PROVISIONS REGARDING (AMONG
OTHER THINGS) THE PAYMENT OF THIS BOND AND VOTING AND TRANSFER RIGHTS WITH
RESPECT TO THIS BOND. THE SECURITY AGREEMENT MAY IMPOSE LIMITATIONS ON THE
AMOUNTS PAYABLE UNDER THIS BOND. THE COMPANY AND (BY THEIR ACCEPTANCE THEREOF)
EACH HOLDER OF THIS BOND AGREE THAT THE RIGHTS OF THE PARTIES WITH RESPECT TO
THIS BOND SHALL IN ALL RESPECTS BE SUBJECT TO SUCH LIMITATIONS AND OTHER
PROVISIONS OF THE SECURITY AGREEMENT.

         NORTHERN STATES POWER COMPANY, a corporation organized and existing
under the laws of the State of Minnesota (the "Company"), for value received,
hereby promises to pay the sum of ______________________ Dollars ($_________),
subject to reductions of principal and limitations on payment as and to the
extent set forth in the Security Agreement (as defined below), to Wells Fargo
Bank, National Association, as Administrative Agent (the "Administrative
Agent"), on behalf of itself and the Banks (as defined below), or registered
assigns, at the office of the Trustee in Chicago, Illinois, or, at the option of
the registered owner, at the agency of the Company in the Borough of Manhattan,
City and State of New York, on May 14, 2004 (the "Maturity Date") or upon
earlier declaration of acceleration or redemption; provided, however, that, in
the event the Commitment Termination Date, under and as defined in the Credit
Agreement (as defined below), is extended in accordance with the terms of the
Credit Agreement, the Maturity Date shall be automatically extended to the date
of such extended Commitment Termination Date and the principal amount of the
bonds of this series shall be automatically reduced to the extent of the
reductions to the Commitment Amounts (as defined in the Credit Agreement), if
any, made in accordance with the Credit Agreement without any further act on the
part of the Company or the holders of the bonds of this series; provided,
further, that the Maturity Date as so extended shall in no event be later than
May 12, 2006 (the Maturity Date or, if extended, the date to which the Maturity
Date shall be extended in accordance with the terms hereof, shall be referred to
as the "Stated Maturity Date"). This bond shall not bear interest. Payment of
the principal on this bond shall be made in the lawful money of the United
States.

         This bond is issued to the Administrative Agent by the Company pursuant
to the Company's obligations under the Credit Agreement dated as of May 16, 2003
(as amended, supplemented, restated, extended or otherwise modified from time to
time, the "Credit Agreement"), among the Company, the Administrative Agent, and
the other banks party thereto from time to time (collectively, the "Banks"),
including any amendments or extensions thereto that may be subsequent to the
date hereof. This bond shall be held by the Administrative Agent subject to the
terms of the Credit Agreement and the Security Agreement dated as of May 16,
2003 between the Company and the Administrative Agent (the "Security
Agreement").

         It shall be an additional term and condition of the bonds of this
series that, in the event (i) an Event of Default under and as defined in the
Credit Agreement has occurred under Section 7.1(a) of the Credit Agreement by
reason of a failure by the Company to make a payment of principal when the same
shall be due and payable pursuant to the Credit Agreement or (ii) the Notes (as
defined in the Credit Agreement) are declared due and payable pursuant to
Section 7.2 of the Credit Agreement, then the occurrence of either such event
shall be deemed, upon written notice from the Administrative Agent to the
Trustee of the occurrence thereof, to be

                                       5
<PAGE>

a completed default, for purposes of Section 1(a) of Article XIII of the
Original Indenture prior to the Effective Date (as defined below), and a
Completed Default, for purposes of Section 13.01(a) of the Indenture on and
after the Effective Date, and the definitions of completed default and Completed
Default in the Original Indenture and the Indenture, respectively, are modified
accordingly for purposes of the bonds of this series.

         The Trustee may conclusively presume that the obligation of the Company
to pay the principal of this bond shall have been fully satisfied and discharged
unless and until it shall have received a written notice from the Administrative
Agent, signed by an authorized officer of the Administrative Agent and attested
by the Secretary or an Assistant Secretary of the Administrative Agent, stating
that the payment of principal of this bond has not been fully paid when due and
specifying the amount of funds required to make such payment.

         This bond has been issued by the Company to the Administrative Agent to
(i) provide for the payment of the Company's obligations to make payments to any
person under the Credit Agreement and (ii) provide to such persons the benefits
of the security provided for this bond pursuant to the Indenture. The
obligations of the Company under the bonds of this series may be discharged
prior to the Stated Maturity Date under the circumstances set forth in the
Security Agreement.

         This bond is one of a duly authorized issue of bonds of the Company, 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 February 1, 1937 (the "1937 Indenture"), as
supplemented by 52 supplemental trust indentures (collectively, the
"Supplemental Indentures" and together with the 1937 Indenture, the "Original
Indenture"), a Supplemental and Restated Trust Indenture dated May 1, 1988 (the
"Restated Indenture") and a new supplemental trust indenture for the bonds of
this series (the "New Supplemental Indenture"), executed by the Company to BNY
Midwest Trust Company, as successor to Harris Trust and Savings Bank, as Trustee
(the "Trustee"). The 1937 Indenture, as supplemented by the Supplemental
Indentures, the Restated Indenture and the New Supplemental Indenture herein are
referred to collectively as the "Indenture". 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 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 default as in the Indenture, including the
New Supplemental Indenture, provided.

         The rights of the holder of this bond to vote or consent under the
Indenture in respect of this bond shall be limited to the extent and in the
manner specified in the Security Agreement. 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 holders of the bonds, and the terms and
provisions of the Indenture and of any instruments supplemental thereto may be
modified or altered by affirmative vote of the holders of at least 80% in
principal amount of the bonds then outstanding under the Indenture and any
instruments supplemental thereto (excluding

                                       6
<PAGE>

bonds challenged and disqualified from voting by reason of the Company's
interest therein as provided in the Indenture); provided that without the
consent of all 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 thereon or any other modification in the terms
of payment of such principal or interest. The foregoing 80% requirement will be
reduced to 66 2/3% when all bonds of each series issued under the Indenture
prior to May 1, 1985, shall have been retired or all the holders thereof shall
have consented to such reduction.

         The Restated Indenture amends and restates the 1937 Indenture and the
Supplemental Indentures. The Restated Indenture will become effective and
operative (the "Effective Date") when all bonds of each series issued under the
Indenture prior to May 1, 1988 shall have been retired through payment or
redemption (including those bonds "deemed to be paid" within the meaning of that
term as used in Article XVII of the 1937 Indenture) or until, subject to certain
exceptions, the holders of the requisite principal amount of such bonds shall
have consented to the amendments contained in the Restated Indenture. Holders of
the bonds of this series and of each subsequent series of bonds issued under the
Indenture likewise will be bound by the amendments contained in the Restated
Indenture when they become effective and operative. Reference is made to the
Restated Indenture for a complete description of the amendments contained
therein to the 1937 Indenture and to the Supplemental Indentures.

         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 and for all other purposes and shall not be affected by any
notice to the contrary.

         Bonds of this series are not redeemable at the option of the Company
prior to the Stated Maturity Date for any reason, and are not subject to a
sinking fund.

         In the event (i) an Event of Default under and as defined in the Credit
Agreement has occurred under Section 7.1(a) of the Credit Agreement by reason of
a failure by the Company to make a payment of principal when the same shall be
due and payable pursuant to the Credit Agreement or (ii) the Notes (as defined
in the Credit Agreement) are declared due and payable pursuant to Section 7.2 of
the Credit Agreement, then the bonds of this series shall be redeemable in whole
upon receipt by the Trustee of a written demand (a "Redemption Demand") from the
Administrative Agent stating that there has been such an Event of Default and
demanding redemption of the bonds of this series. The Trustee shall, within 5
days after receiving such Redemption Demand, mail a copy thereof to the Company
and the Administrative Agent marked to indicate the date of its receipt by the
Trustee. Promptly upon receipt by the Company of such copy of a Redemption
Demand, the Company shall fix a date on which it will redeem the bonds of this
series so demanded to be redeemed (the "Demand Redemption Date"). Notice of the
date fixed as and for the Demand Redemption Date shall be mailed by the Company
to the Trustee and the Administrative Agent at least 5 days prior to such Demand
Redemption Date. The date to be fixed by the Company as and for the Demand
Redemption Date may be any date up to and including the earlier of (i) the 15th
day after receipt by the Trustee of the Redemption Demand or (ii) the Stated
Maturity Date; provided, however, that if the Trustee and the Administrative
Agent shall not have received such notice fixing the Demand Redemption Date
within 10 days after receipt by the Trustee of the Redemption Demand, the Demand
Redemption Date shall be deemed to be the earlier of (i) the 15th day after
receipt by the

                                       7
<PAGE>

Trustee of the Redemption Demand or (ii) the Stated Maturity Date.
Notwithstanding the foregoing, if an Event of Default or acceleration of Notes
to which this paragraph is applicable is existing on the Stated Maturity Date,
such date shall be deemed to be the Demand Redemption Date without further
action (including actions specified in this paragraph) by the Administrative
Agent, the Trustee or the Company. The bonds of this series shall be redeemed by
the Company on the Demand Redemption Date, upon surrender thereof by the
Administrative Agent to the Trustee, at a redemption price equal to the
principal amount thereof. If a Redemption Demand is rescinded by the
Administrative Agent by written notice to the Trustee prior to the Demand
Redemption Date, no notice of the Demand Redemption Date shall be given, or, if
already given, shall be automatically annulled; but no such rescission shall
extend to or affect any subsequent Event of Default or acceleration of Notes or
impair any right consequent thereon.

         This bond is subject to restrictions on transferability as set forth in
the Security Agreement. This bond is transferable only in accordance with the
provisions of the Security Agreement and the Indenture by the registered owner
hereof in person, or by his duly authorized attorney, at the office of the
Trustee in Chicago, Illinois, or at the option of the registered owner at the
agency of the Company in the Borough of Manhattan, City and State of New York,
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.

         No recourse shall be had for the payment of the principal of 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 BNY Midwest Trust Company, as Trustee under the Indenture, or
its successor thereunder.

                                       8
<PAGE>

         IN WITNESS WHEREOF, NORTHERN STATES POWER COMPANY has caused this bond
to be executed 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.

Dated as of _________________               NORTHERN STATES POWER COMPANY

Attest:___________________________          By:_________________________________
        Secretary                                  President

                         (Form of Trustee's Certificate)

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

                                            BNY MIDWEST TRUST COMPANY,
                                            As Trustee,

                                            By:_________________________________
                                              Authorized Officer

and

         WHEREAS, the Company has acquired no additional property subsequent to
the date of the preparation of the Supplemental Trust Indenture dated as of
August 1, 2002 to be conveyed, assigned, transferred, mortgaged, pledged, set
over and confirmed to the Trustee and to its respective successors in trust
hereunder; 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 particulars of any new series of bonds
and of providing the terms and conditions of the issue of the bonds of any
series not expressly provided for in the Indenture and for any other purpose not
inconsistent with the terms of the Indenture; and

         WHEREAS, the execution and delivery of this Supplemental Trust
Indenture has been duly authorized by a resolution adopted by the Board of
Directors of the Company; and

         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 BNY Midwest Trust Company, as

                                       9
<PAGE>

Trustee, and its successors in the trust under the Indenture for the benefit of
those who hold or shall hold the bonds, or any of them, issued or to be issued
thereunder as follows:

                                   ARTICLE I.
                           FORM AND EXECUTION OF BONDS

         SECTION 1.01. There hereby is created, for issuance under the
Indenture, a series of bonds designated Series due 2004, extendible through 2006
in the aggregate principal amount of $275,000,000, which shall bear the
descriptive title "First Mortgage Bonds, Series due 2004, extendible through
2006" (the "Bonds"), and the form thereof shall contain suitable provisions with
respect to the matters hereafter specified in this Section. The Bonds shall be
issued as registered bonds without coupons in denominations of a multiple of
$1,000 and shall be substantially of the tenor and purport hereinbefore recited.
The principal amount of the Bonds shall be payable on May 14, 2004 (the
"Maturity Date") or upon earlier declaration of acceleration or redemption;
provided, however, that in the event the Commitment Termination Date, under and
as defined in the Credit Agreement, is extended in accordance with the terms of
the Credit Agreement, the Maturity Date shall be automatically extended to the
date of such extended Commitment Termination Date and the principal amount of
the Bonds shall be automatically reduced to the extent of the reductions to the
Commitment Amounts (as defined in the Credit Agreement), if any, made in
accordance with the Credit Agreement without any further act on the part of the
Company or the holders of the Bonds; provided, further, that the Maturity Date
as so extended shall in no event be later than May 12, 2006 (the Maturity Date
or, if extended, the date to which the Maturity Date shall be extended in
accordance with the terms hereof, shall be referred to as the "Stated Maturity
Date"). The Bonds shall not bear interest. Principal on the Bonds shall be
payable at the office of the Trustee in Chicago, Illinois, or, at the option of
the registered owner, at the agency of the Company in the Borough of Manhattan,
City and State of New York. Payment of the principal on the Bonds shall be made
in the lawful money of the United States. Payment of principal on the Bonds
shall be subject to the limitations imposed by the Security Agreement dated as
of May 16, 2003 between the Company and the Administrative Agent (the "Security
Agreement").

         The Bonds are being issued to the Administrative Agent by the Company
pursuant to the Company's obligations under the Credit Agreement and shall be
held by the Administrative Agent subject to the terms of the Credit Agreement
and the Security Agreement.

         It shall be an additional term and condition of the Bonds that, in the
event (i) an Event of Default under and as defined in the Credit Agreement has
occurred under Section 7.1(a) of the Credit Agreement by reason of a failure by
the Company to make a payment of principal when the same shall be due and
payable pursuant to the Credit Agreement or (ii) the Notes (as defined in the
Credit Agreement) are declared due and payable pursuant to Section 7.2 of the
Credit Agreement, then the occurrence of either such event shall be deemed, upon
written notice from the Administrative Agent to the Trustee of the occurrence
thereof, to be a completed default, for purposes of Section 1(a) of Article XIII
of the Original Indenture prior to the Effective Date, and a Completed Default,
for purposes of Section 13.01(a) of the Indenture on and after the Effective
Date, and the definitions of completed default and Completed Default in the
Original Indenture and the Indenture, respectively, are modified accordingly for
purposes of the Bonds.

                                       10
<PAGE>

         The Bonds have been issued by the Company to the Administrative Agent
to (i) provide for the payment of the Company's obligations to make payments to
any person under the Credit Agreement and (ii) provide to such persons the
benefits of the security provided for the Bonds pursuant to the Indenture. The
obligations of the Company under the Bonds may be discharged prior to the Stated
Maturity Date under the circumstances set forth in the Security Agreement.

         SECTION 1.02. The Bonds are not redeemable by the Company prior to the
Stated Maturity Date for any reason and are not subject to a sinking fund.

         In the event (i) an Event of Default under and as defined in the Credit
Agreement has occurred under Section 7.1(a) of the Credit Agreement by reason of
a failure by the Company to make a payment of principal when the same shall be
due and payable pursuant to the Credit Agreement or (ii) the Notes (as defined
in the Credit Agreement) are declared due and payable pursuant to Section 7.2 of
the Credit Agreement, then the Bonds shall be redeemable in whole upon receipt
by the Trustee of a written demand (a "Redemption Demand") from the
Administrative Agent stating that there has been such an Event of Default and
demanding redemption of the Bonds. The Trustee shall, within 5 days after
receiving such Redemption Demand, mail a copy thereof to the Company and the
Administrative Agent marked to indicate the date of its receipt by the Trustee.
Promptly upon receipt by the Company of such copy of a Redemption Demand, the
Company shall fix a date on which it will redeem the Bonds so demanded to be
redeemed (the "Demand Redemption Date"). Notice of the date fixed as and for the
Demand Redemption Date shall be mailed by the Company to the Trustee and the
Administrative Agent at least 5 days prior to such Demand Redemption Date. The
date to be fixed by the Company as and for the Demand Redemption Date may be any
date up to and including the earlier of (i) the 15th day after receipt by the
Trustee of the Redemption Demand or (ii) the Stated Maturity Date; provided,
however, that if the Trustee and the Administrative Agent shall not have
received such notice fixing the Demand Redemption Date within 10 days after
receipt by the Trustee of the Redemption Demand, the Demand Redemption Date
shall be deemed to be the earlier of (i) the 15th day after receipt by the
Trustee of the Redemption Demand or (ii) the Stated Maturity Date.
Notwithstanding the foregoing, if an Event of Default or acceleration of Notes
to which this paragraph is applicable is existing on the Stated Maturity Date,
such date shall be deemed to be the Demand Redemption Date without further
action (including actions specified in this paragraph) by the Administrative
Agent, the Trustee or the Company. The Bonds shall be redeemed by the Company on
the Demand Redemption Date, upon surrender thereof by the Administrative Agent
to the Trustee, at a redemption price equal to the principal amount thereof. If
a Redemption Demand is rescinded by the Administrative Agent by written notice
to the Trustee prior to the Demand Redemption Date, no notice of the Demand
Redemption Date shall be given, or, if already given, shall be automatically
annulled; but no such rescission shall extend to or affect any subsequent Event
of Default or acceleration of Notes or impair any right consequent thereon.

         SECTION 1.03. The registered owner of any Bond or Bonds, at his option
may surrender the same with other Bonds of such series at the office of the
Trustee in Chicago, Illinois, or at the agency of the Company in the Borough of
Manhattan, City and State of New York, or elsewhere if authorized by the
Company, for cancellation, in exchange for other Bonds of such series of higher
or lower authorized denominations, but of the same aggregate principal amount,
and upon receipt of any payment required under the provisions of Section 1.04
hereof. Thereupon the

                                       11
<PAGE>

Company shall execute and deliver to the Trustee and the Trustee shall
authenticate and deliver such other registered bonds to such registered owner at
its office or at any other place specified as aforesaid.

         SECTION 1.04. No charge shall be made by the Company for any exchange
or transfer of Bonds, other than for taxes or other governmental charges, if
any, that may be imposed in relation thereto.

         SECTION 1.05. The Bonds shall be executed on behalf of the Company by
the manual signature of its President or one of its Vice Presidents or with the
facsimile signature of its President, and its corporate seal shall be thereunto
affixed, or printed, lithographed, or engraved thereon, in facsimile, and
attested by the manual signature of its Secretary or one of its Assistant
Secretaries or with the facsimile signature of its Secretary. In case any of the
officers who shall have signed any Bonds or attested the seal thereon or whose
facsimile signature shall be borne by the Bonds shall cease to be such officers
of the Company before the Bonds so signed and sealed actually shall have been
authenticated by the Trustee or delivered by the Company, such Bonds
nevertheless may be issued, authenticated, and delivered with the same force and
effect as though the person or persons who signed such Bonds and attested the
seal thereon or whose facsimile signature is borne by the Bonds had not ceased
to be such officer or officers of the Company. Any Bond issuable hereunder may
be signed or attested by manual or facsimile signature on behalf of the Company
by such person as at the actual date of the execution of such Bond shall be the
proper officer of the Company, although at the date of such Bond such person
shall not have been an officer of the Company.

         SECTION 1.06. The registered holder of all of the Bonds shall be the
Administrative Agent until such time as the Bonds are transferred in accordance
with the Security Agreement and the Indenture.

                                   ARTICLE II.
                      APPOINTMENT OF AUTHENTICATING AGENT.

         SECTION 2.01. The Trustee shall, if requested in writing so to do by
the Company, promptly appoint an agent or agents of the Trustee who shall have
authority to authenticate registered Bonds, in the name and on behalf of the
Trustee. Such appointment by the Trustee shall be evidenced by a certificate of
a vice-president of the Trustee delivered to the Company prior to the
effectiveness of such appointment.

         SECTION 2.02. (a) Any such authenticating agent shall be acceptable to
the Company and at all times shall be a corporation which is organized and doing
business under the laws of the United States or of any State, is authorized
under such laws to act as authenticating agent, has a combined capital and
surplus of at least $10,000,000, and is subject to supervision or examination by
Federal or State authority. If such corporation publishes reports of condition
at least annually, pursuant to law or to the requirements of the aforesaid
supervising or examining authority, then for the purposes of this Section 2.02
the combined capital and surplus of such corporation shall be deemed to be its
combined capital and surplus as set forth in its most recent report of condition
so published.

                                       12
<PAGE>

         (b)      Any corporation into which any authenticating agent may be
merged or converted or with which it may be consolidated, or any corporation
resulting from any merger, conversion, or consolidation to which any
authenticating agent shall be a party, or any corporation succeeding to the
corporate agency business of any authenticating agent, shall continue to be the
authenticating agent without the execution or filing of any paper or any further
act on the part of the Trustee or the authenticating agent.

         (c)      Any authenticating agent at any time may resign by giving
written notice of resignation to the Trustee and to the Company. The Trustee may
at any time, and upon written request of the Company to the Trustee shall,
terminate the agency of any authenticating agent by giving written notice of
termination to such authenticating agent and to the Company. Upon receiving such
a notice of resignation or upon such a termination, or in case at any time any
authenticating agent shall cease to be eligible in accordance with the
provisions of this Section 2.02, the Trustee, unless otherwise requested in
writing by the Company, promptly shall appoint a successor authenticating agent,
which shall be acceptable to the Company. Any successor authenticating agent
upon acceptance of its appointment hereunder shall become vested with all the
rights, powers, duties, and responsibilities of its predecessor hereunder, with
like effect as if originally named. No successor authenticating agent shall be
appointed unless eligible under the provisions of this Section 2.02.

         (d)      The Company agrees to pay to any authenticating agent,
appointed in accordance with the provisions of this Section 2.02, reasonable
compensation for its services.

         SECTION 2.03. If an appointment is made pursuant to this Article II,
the registered Bonds, shall have endorsed thereon, in addition to the Trustee's
Certificate, an alternate Trustee's Certificate in the following form:

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

                           BNY MIDWEST TRUST COMPANY,
                                   as Trustee,

                                               By______________________________
                                                        Authenticating Agent,

                                               By______________________________
                                                        Authorized Officer.

         SECTION 2.04. No provision of this Article II shall require the Trustee
to have at any time more than one such authenticating agent for any one State or
to appoint any such authenticating agent in the State in which the Trustee has
its principal place of business.

                                       13
<PAGE>

                                  ARTICLE III.
                          FINANCING STATEMENT TO COMPLY
                        WITH THE UNIFORM COMMERCIAL CODE.

         SECTION 3.01. The name and address of the debtor and secured party are
set forth below:

                  Debtor:                   Northern States Power Company
                                            414 Nicollet Mall
                                            Minneapolis, Minnesota 55401

                  Secured Party:            BNY Midwest Trust Company, Trustee
                                            2 North LaSalle Street
                                            Suite 1020
                                            Chicago, Illinois  60602

         NOTE: Northern States Power Company, the debtor above named, is "a
transmitting utility" under the Uniform Commercial Code as adopted in Minnesota,
North Dakota and South Dakota.

         SECTION 3.02. The maturity dates and respective principal amounts of
obligations of the debtor secured and presently to be secured by the Indenture,
reference to all of which for the terms and conditions thereof is hereby made
with the same force and effect as if incorporated herein at length, are as
follows.

<TABLE>
<CAPTION>
    FIRST MORTGAGE BONDS                         PRINCIPAL AMOUNT
---------------------------                      ----------------
<S>                                              <C>
Series due December 1, 2005                        $ 70,000,000
Pollution Control Series J                         $  5,450,000
Pollution Control Series K                         $  3,400,000
Pollution Control Series L                         $  4,850,000
Series due July 1, 2025                            $250,000,000
Pollution Control Series N                         $ 27,900,000
Pollution Control Series O                         $ 50,000,000
Pollution Control Series P                         $ 50,000,000
Series due March 1, 2028                           $150,000,000
Resource Recovery Series Q                         $ 15,170,000
Resource Recovery Series R                         $ 19,615,000
Series Due August 15, 2003                         $308,000,000
Pollution Control Series S                         $ 69,000,000
Series A and Series B due August 28, 2012          $450,000,000
Series due 2004, extendible through 2006           $275,000,000
</TABLE>

         SECTION 3.03. This Financing Statement is hereby adopted for all of the
First Mortgage Bonds of the series mentioned above secured by said Indenture.

         SECTION 3.04. The 1937 Indenture and the prior Supplemental Trust
Indentures, as set forth below, have been filed or recorded in each and every
office in the States of Minnesota,

                                       14
<PAGE>

North Dakota, and South Dakota designated by law for the filing or recording
thereof in respect of all property of the Company subject thereto:

         Original Indenture
                Dated February 1, 1937

         Supplemental Indenture
                Dated June 1, 1942

         Supplemental Indenture
                Dated February 1, 1944

         Supplemental Indenture
                Dated October 1, 1945

         Supplemental Indenture
                Dated July 1, 1948

         Supplemental Indenture
                Dated August 1, 1949

         Supplemental Indenture
                Dated June 1, 1952

         Supplemental Indenture
                Dated October 1, 1954

         Supplemental Indenture
                Dated September 1, 1956

         Supplemental Indenture
                Dated August 1, 1957

         Supplemental Indenture
                Dated July 1, 1958

         Supplemental Indenture
                Dated December 1, 1960

         Supplemental Indenture
                Dated August 1, 1961

         Supplemental Indenture
                Dated June 1, 1962

         Supplemental Indenture
                Dated September 1, 1963

                                       15
<PAGE>

         Supplemental Indenture
                Dated August 1, 1966

         Supplemental Indenture
                Dated June 1, 1967

         Supplemental Indenture
                Dated October 1, 1967

         Supplemental Indenture
                Dated May 1, 1968

         Supplemental Indenture
                Dated October 1, 1969

         Supplemental Indenture
                Dated February 1, 1971

         Supplemental Indenture
                Dated May 1, 1971

         Supplemental Indenture
                Dated February 1, 1972

         Supplemental Indenture
                Dated January 1, 1973

         Supplemental Indenture
                Dated January 1, 1974

         Supplemental Indenture
                Dated September 1, 1974

         Supplemental Indenture
                Dated April 1, 1975

         Supplemental Indenture
                Dated May 1, 1975

         Supplemental Indenture
                Dated March 1, 1976

         Supplemental Indenture
                Dated June 1, 1981

         Supplemental Indenture
                Dated December 1, 1981

                                       16
<PAGE>

         Supplemental Indenture
                Dated May 1, 1983

         Supplemental Indenture
                Dated December 1, 1983

         Supplemental Indenture
                Dated September 1, 1984

         Supplemental Indenture
                Dated December 1, 1984

         Supplemental Indenture
                Dated May 1, 1985

         Supplemental Indenture
                Dated September 1, 1985

         Supplemental and Restated Indenture
                Dated May 1, 1988

         Supplemental Indenture
                Dated July 1, 1989

         Supplemental Indenture
                Dated June 1, 1990

         Supplemental Indenture
                Dated October 1, 1992

         Supplemental Indenture
                Dated April 1, 1993

         Supplemental Indenture
                Dated December 1, 1993

         Supplemental Indenture
                Dated February 1, 1994

         Supplemental Indenture
                Dated October 1, 1994

         Supplemental Indenture
                Dated June 1, 1995

         Supplemental Indenture
                Dated April 1, 1997

                                       17
<PAGE>

         Supplemental Indenture
                Dated March 1, 1998

         Supplemental Indenture
                Dated May 1, 1999

         Supplemental Indenture
                Dated June 1, 2000

         Supplemental Indenture
                Dated August 1, 2000

         Supplemental Indenture
                Dated June 1, 2002

         Supplemental Indenture
                Dated July 1, 2002

         Supplemental Indenture
                Dated August 1, 2002

                                   ARTICLE IV.
                             AMENDMENTS TO INDENTURE

         SECTION 4.01. Each holder or registered owner of a bond of any series
originally authenticated by the Trustee and originally issued by the Company
subsequent to May 1, 1985 and of any coupon pertaining to any such bond, by the
acquisition, holding or ownership of such bond and coupon, thereby consents and
agrees to, and shall be bound by, the provisions of Article VI of the
Supplemental Indenture dated May 1, 1985. Each holder or registered owner of a
bond of any series (including the Bonds) originally authenticated by the Trustee
and originally issued by the Company subsequent to May 1, 1988 and of any coupon
pertaining to such bond, by the acquisition, holding or ownership of such bond
and coupon, thereby consents and agrees to, and shall be bound by, the
provisions of the Supplemental and Restated Trust Indenture dated May 1, 1988
upon the Effective Date.

                                   ARTICLE V.
                                 MISCELLANEOUS.

         SECTION 5.01. The recitals of fact herein, except the recital that the
Trustee has duly determined to execute this Supplemental Trust Indenture and be
bound, insofar as it may lawfully so do, by the provisions hereof and in the
bonds shall be taken as statements of the Company and shall not be construed as
made by the Trustee. The Trustee makes no representations as to value of any of
the property subjected to the lien of the Indenture, or any part thereof, or as
to the title of the Company thereto, or as to the security afforded thereby and
hereby, or as to the validity of this Supplemental Trust Indenture or of the
bonds issued under the Indenture by virtue hereof (except the Trustee's
certificate), and the Trustee shall incur no responsibility in respect of such
matters.

                                       18
<PAGE>

         SECTION 5.02. This Supplemental Trust Indenture shall be construed in
connection with and as a part of the 1937 Indenture, as supplemented by the
Supplemental Trust Indentures dated June 1, 1942, February 1, 1944, October 1,
1945, July 1, 1948, August 1, 1949, June 1, 1952, October 1, 1954, September 1,
1956, August 1, 1957, July 1, 1958, December 1, 1960, August 1, 1961, June 1,
1962, September 1, 1963, August 1, 1966, June 1, 1967, October 1, 1967, May 1,
1968, October 1, 1969, February 1, 1971, May 1, 1971, February 1, 1972, January
1, 1973, January 1, 1974, September 1, 1974, April 1, 1975, May 1, 1975, March
1, 1976, June 1, 1981, December 1, 1981, May 1, 1983, December 1, 1983,
September 1, 1984, December 1, 1984, May 1, 1985, September 1, 1985, the
Supplemental and Restated Trust Indenture dated May 1, 1988 and the Supplemental
Trust Indentures dated July 1, 1989, June 1, 1990, October 1, 1992, April 1,
1993, December 1, 1993, February 1, 1994, October 1, 1994, June 1, 1995, April
1, 1997, March 1, 1997, March 1, 1998, May 1, 1999, June 1, 2000, August 1,
2000, June 1, 2002, July 1, 2002 and August 1, 2002.

         SECTION 5.03. (a) If any provision of the Indenture or this
Supplemental Trust Indenture limits, qualifies, or conflicts with another
provision of the Indenture required to be included in indentures qualified under
the Trust Indenture Act of 1939 (as enacted prior to the date of this
Supplemental Trust Indenture) by any of the provisions of Sections 310 to 317,
inclusive, of the said Act, such required provisions shall control.

         (b)      In case any one or more of the provisions contained in this
Supplemental Trust Indenture or in the bonds issued hereunder should be invalid,
illegal, or unenforceable in any respect, the validity, legality, and
enforceability of the remaining provisions contained herein and therein shall
not in any way be affected, impaired, prejudiced, or disturbed thereby.

         SECTION 5.04. Wherever in this Supplemental Trust Indenture the word
"Indenture" is used without the prefix, "1937," "Original" or "Supplemental",
such word was used intentionally to include in its meaning both the 1937
Indenture and all indentures supplemental thereto.

         SECTION 5.05. Wherever in this Supplemental Trust Indenture either of
the parties hereto is named or referred to, this shall be deemed to include the
successors or assigns of such party, and all the covenants and agreements in
this Supplemental Trust Indenture contained by or on behalf of the Company or by
or on behalf of the Trustee shall bind and inure to the benefit of the
respective successors and assigns of such parties, whether so expressed or not.

         SECTION 5.06. (a) This Supplemental Trust Indenture may be executed
simultaneously in several counterparts, and all said counterparts executed and
delivered, each as an original, shall constitute but one and the same
instrument.

         (b)      The Table of Contents and the descriptive headings of the
several Articles of this Supplemental Trust Indenture were formulated, used, and
inserted in this Supplemental Trust Indenture for convenience only and shall not
be deemed to affect the meaning or construction of any of the provisions hereof.

         The principal amount of obligations to be issued forthwith under the
Indenture is $275,000,000.

                                       19
<PAGE>

         IN WITNESS WHEREOF, on this 5th day of May, 2003, NORTHERN STATES POWER
COMPANY, a Minnesota corporation, party of the first part, has caused its
corporate name and seal to be hereunto affixed, and this Supplemental Trust
Indenture dated as of May 1, 2003, to be signed by its President or a Vice
President, and attested by its Secretary or an Assistant Secretary, for and in
its behalf, and BNY Midwest Trust Company, an Illinois corporation, as Trustee,
party of the second part, to evidence its acceptance of the trust hereby
created, has caused its corporate name and seal to be hereunto affixed, and this
Supplemental Trust Indenture dated as of May 1, 2003, to be signed by its
President, a Vice President, or an Assistant Vice President, and attested by its
Secretary, an Assistant Secretary, or an Assistant Vice President for and in its
behalf.

                                      NORTHERN STATES POWER COMPANY

                                      /s/ BENJAMIN G.S. FOWKE III
                                      -----------------------------
                                      By: Benjamin G.S. Fowke III
                                          Its: Vice President and Treasurer

Attest:

/s/ NANCY HALEY
--------------------------
Nancy Haley
Assistant Secretary

Executed by Northern States Power Company
   in presence of:

/s/ MARY SCHELL                                                 (CORPORATE SEAL)
--------------------------
Mary Schell, Witness

/s/ ELIZABETH BLOHM
--------------------------
Elizabeth Blohm, Witness

                                       20
<PAGE>

                                          BNY MIDWEST TRUST COMPANY, as
                                          Trustee

                                          /s/ J. BARTOLINI
                                          --------------------------
                                          By: J. Bartolini
                                              Its: Vice President

Attest:

/s/ C. POTTER
--------------------------
Name: C. Potter
 Its: Assistant Secretary

Executed by BNY Midwest Trust Company in
   presence of:

/s/ M CALLAHAN
--------------------------
M. Callahan, Witness                                            (CORPORATE SEAL)

/s/ D.G. DONOVAN
--------------------------
D. G. Donovan, Witness


                                       21
<PAGE>

STATE OF MINNESOTA                       )
                                         ) ss.
COUNTY OF HENNEPIN                       )

         On this 5th day of May, A.D. 2003, before me, Sharon Quellhorst, a
Notary Public in and for said County in the State aforesaid, personally appeared
Benjamin G.S. Fowke III and Nancy Haley, to me personally known, and to me known
to be Vice President and Treasurer and Assistant Secretary, respectively, of
Northern States Power Company, one of the corporations described in and which
executed the within and foregoing instrument, and who, being by me severally
duly sworn, each did say that he, the said Benjamin G.S. Fowke III is Vice
President and Treasurer, and she, the said Nancy Haley, is Assistant Secretary,
of said Northern States Power Company, a corporation; that the seal affixed to
the within and foregoing instrument is the corporate seal of said corporation,
and that said instrument was executed in behalf of said corporation by authority
of its board of directors; and said Benjamin G.S. Fowke III and Nancy Haley each
acknowledged said instrument to be the free act and deed of said corporation and
that such corporation executed the same.

         WITNESS my hand and notarial seal this 5th day of May, A.D. 2003.

/s/ SHARON M. QUELLHORST                                        (NOTARY SEAL)
--------------------------
Sharon Quellhorst
Notary Public
My commission expires January 31, 2005

                                       22
<PAGE>

STATE OF MINNESOTA             )
                               ) ss.
COUNTY OF HENNEPIN             )

         Benjamin G.S. Fowke III and Nancy Haley, being severally duly sworn,
each deposes and says that he, the said Benjamin G.S. Fowke III , is Vice
President and Treasurer, and she, the said Nancy Haley, is Assistant Secretary,
of Northern States Power Company, the corporation described in and which
executed the within and foregoing Supplemental Trust Indenture, as mortgagor;
and each for himself or herself further says that said Supplemental Trust
Indenture was executed in good faith, and not for the purpose of hindering,
delaying, or defrauding any creditor of the said mortgagor.

/s/ BENJAMIN G.S. FOWKE III                  /s/ NANCY HALEY
---------------------------                  --------------------------
Benjamin G.S. Fowke III                      Nancy Haley

         Subscribed and sworn to before me this 5th day of May, A.D. 2003.

/s/ SHARON M. QUELLHORST                                           (NOTARY SEAL)
---------------------------
Sharon Quellhorst
Notary Public
My commission expires January 31, 2005

                                       23
<PAGE>

STATE OF ILLINOIS          )
                           ) ss.
COUNTY OF COOK             )

         On this 6th day of May, A.D. 2003, before me, A. Hernandez, a Notary
Public in and for said County in the State aforesaid, personally appeared J.
Bartolini and C. Potter, to me personally known, and to me known to be Vice
President and Assistant Secretary, respectively, of BNY Midwest Trust Company,
one of the corporations described in and which executed the within and foregoing
instrument, and who, being by me severally duly sworn, each, did say that she,
the said J. Bartolini is Vice President, and she, the said C. Potter, is
Assistant Secretary, of said BNY Midwest Trust Company, a corporation; that the
seal affixed to the within and foregoing instrument is the corporate seal of
said corporation, and that said instrument was executed in behalf of said
corporation by authority of its board of directors; and said J. Bartolini and C.
Potter each acknowledged said instrument to be the free act and deed of said
corporation and that such corporation executed the same.

         WITNESS my hand and notarial seal this 6th day of May, A.D. 2003.

/s/ A. HERNANDEZ                                                   (NOTARY SEAL)
--------------------------
Notary Public
My commission expires 7/8/06

                                       24
<PAGE>

STATE OF ILLINOIS          )
                           ) ss.
COUNTY OF COOK             )

         J. Bartolini and C. Potter, being severally duly sworn, each for
herself deposes and says that she, the said J. Bartolini, is Vice President, and
she, the said C. Potter, is Assistant Secretary, of BNY Midwest Trust Company,
the corporation described in and which executed the within and foregoing
Supplemental Trust Indenture, as mortgagee, and each for herself further says
that said Supplemental Trust Indenture was executed in good faith, and not for
the purpose of hindering, delaying, or defrauding any creditor of the mortgagor.

/s/ J. BARTOLINI                            /s/ C. POTTER
--------------------------                  --------------------------
Name: J. Bartolini                          Name: C. Potter

         Subscribed and sworn to before me this 6th day of May, A.D. 2003.

/s/ A. HERNANDEZ                                                   (NOTARY SEAL)
--------------------------
Notary Public
My commission expires 7/8/06

                                       25
<PAGE>

         This instrument was drafted by Northern States Power Company, 414
Nicollet Mall, Minneapolis, Minnesota 55401.

         Tax statements for the real property described in this instrument
should be sent to Northern States Power Company, 414 Nicollet Mall, Minneapolis,
Minnesota 55401.

         Please return recorded document(s) to Lori R. Pagel, GO-Mezzanine, Xcel
Energy, 414 Nicollet Mall, Minneapolis, Minnesota 55401.