<PAGE>

                                                                    Exhibit 4.06



                          SUPPLEMENTAL TRUST INDENTURE


                                      FROM


                          NORTHERN STATES POWER COMPANY


                                       TO


                            BNY MIDWEST TRUST COMPANY
                                     TRUSTEE


                                  ------------

                               DATED JULY 1, 2002


                                  ------------

                         SUPPLEMENTAL TO TRUST INDENTURE
                             DATED FEBRUARY 1, 1937


                                       AND


                            SUPPLEMENTAL AND RESTATED
                                 TRUST INDENTURE
                                DATED MAY 1, 1988



<PAGE>


<TABLE>
<CAPTION>
                                                                                                               PAGE

<S>               <C>                                                                                         <C>
ARTICLE I.        SPECIFIC SUBJECTION OF ADDITIONAL PROPERTY TO THE LIEN OF THE ORIGINAL INDENTURE...............9

         Section 1.01.     ......................................................................................9

ARTICLE II.       PROVISIONS OF BONDS OF POLLUTION CONTROL SERIES S.............................................11

         Section 2.01.     .....................................................................................11

         Section 2.02.     .....................................................................................11

         Section 2.03.     .....................................................................................12

         Section 2.04.     .....................................................................................13

         Section 2.05.     .....................................................................................13

ARTICLE III.      FINANCING STATEMENT TO COMPLY WITH THE UNIFORM COMMERCIAL CODE................................13

         Section 3.01.     .....................................................................................13

         Section 3.02.     .....................................................................................13

         Section 3.03.     .....................................................................................13

         Section 3.04.     .....................................................................................14

         Section 3.05.     .....................................................................................14

         Section 3.06.     .....................................................................................17

ARTICLE IV.       AMENDMENTS TO INDENTURE.......................................................................17

         Section 4.01.     .....................................................................................17

ARTICLE V.        MISCELLANEOUS.................................................................................18

         Section 5.01.     .....................................................................................18

         Section 5.02.     .....................................................................................18

         Section 5.03.     .....................................................................................18

         Section 5.04.     .....................................................................................19

         Section 5.05.     .....................................................................................19

         Section 5.06.     .....................................................................................19

         Schedule A        ....................................................................................A-1
</TABLE>


                                      -i-

<PAGE>




         SUPPLEMENTAL TRUST INDENTURE, MADE AS OF THE 1ST DAY OF JULY, 2002, 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,
Minnesota (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, Illinois, successor to Harris Trust and Savings Bank, as Trustee (the
"Trustee"), party of the second part;

WITNESSETH:

         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"), has heretofore 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 the provisions
of the 1937 Indenture for the equal pro rata benefit and security of all and
each of the bonds issued and to be 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>                                 <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)
</TABLE>


<PAGE>
<TABLE>
<CAPTION>
                 DATE OF SUPPLEMENTAL
                   TRUST INDENTURE                   DESIGNATION OF SERIES
                 ------------------                  ---------------------
<S>              <C>                                 <C>
                 June 1, 1952                        Series due June 1, 1982 (retired)
                 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
                 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, and March 1, 2028
                 May 1, 1999                         Resource Recovery Series Q
                 June 1, 2000                        Resource Recovery Series R
                 June 1, 2002                        Series due August 15, 2003; 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 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 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


                                       3
<PAGE>




         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 City of Becker, in the County of Sherburne, a municipal
corporation existing under the Constitution and laws of the State of Minnesota
(the "City") has issued $69,000,000 principal amount of its Pollution Control
Revenue Refunding Bonds (Northern States Power Company - Sherburne County
Generating Station Units 1 and 2 Project), Series 2000-A (the "Pollution Control
Revenue Bonds") pursuant to the provisions of the Indenture of Trust, dated as
of March 1, 2000, as supplemented by Supplemental Indenture No. 1, dated as of
August 1, 2002, and Supplemental Indenture No. 2, dated as of August 20, 2002
(as supplemented, the "Pollution Control Indenture"), between the City and Wells
Fargo Bank Minnesota, National Association, as Trustee (said Trustee or any
successor trustee under the Pollution Control Indenture being hereinafter
referred to as the "Pollution Control Trustee"); and

         WHEREAS, the net proceeds of the Pollution Control Revenue Bonds were
loaned by the City to the Company pursuant to the provisions of a Loan Agreement
dated as of March 1, 2000, between the City and the Company (as amended, the
"Agreement"), to provide a portion of the funds to refinance the acquisition,
construction and equipping of certain air and water pollution control facilities
relating to the first and second electric generating units located in the City
at the Company's Sherburne County Generating Station, owned jointly by the
Company and Southern Minnesota Municipal Power Agency; and

         WHEREAS, payments by the Company under and pursuant to the Agreement
have been assigned by the City to the Pollution Control Trustee in order to
secure the payment of the Pollution Control Revenue Bonds; and

         WHEREAS, in order to further secure the payment of the Pollution
Control Revenue Bonds, the Company desires to provide for the issuance under the
Indenture to the Pollution Control Trustee of a new series of bonds designated
"First Mortgage Bonds, Pollution Control Series S" (sometimes called "Bonds of
Pollution Control Series S"), in a principal amount equal to the principal
amount of the Pollution Control Revenue Bonds, and with corresponding terms and
maturity, the Bonds of Pollution Control Series S to be issued as registered
bonds without coupons in denominations of a multiple of $5,000; and

         WHEREAS, the Bonds of Pollution Control Series S are to be
substantially in the form and tenor following, to-wit:

                  (Form of Bonds of Pollution Control Series S)

         This Bond has not been registered under the Securities Act of 1933, as
amended, and may not be offered or sold in contravention of said Act and is not
transferable except to a successor Trustee under the Indenture of Trust dated as
of March 1, 2000, as amended, from the City of Becker, Minnesota (the "City"),
to Wells Fargo Bank Minnesota, National Association, as Trustee.



                                       4

<PAGE>




                          NORTHERN STATES POWER COMPANY

             (Incorporated under the laws of the State of Minnesota)

                               First Mortgage Bond

                           Pollution Control Series S

No._________                                                         $69,000,000

         Northern States Power Company, a corporation organized and existing
under and by virtue of the laws of the State of Minnesota (herein called the
"Company"), for value received, hereby promises to pay to Wells Fargo Bank
Minnesota, National Association, Minneapolis, Minnesota, as Trustee under the
Indenture of Trust dated as of March 1, 2000, as supplemented by Supplemental
Indenture No. 1, dated as of August 1, 2002, and Supplemental Indenture No. 2,
dated as of August 20, 2002 (as supplemented, the "Pollution Control Indenture")
from the City of Becker, Minnesota (the "City"), to Wells Fargo Bank Minnesota,
National Association, Minneapolis, Minnesota, or any successor trustee under the
Pollution Control Indenture (the "Pollution Control Trustee") and at the office
of BNY Midwest Trust Company, Chicago, Illinois, successor to Harris Trust and
Savings Bank, as trustee (the "Trustee") the sum of Sixty-Nine Million Dollars
in lawful money of the United States of America on the Demand Redemption Date,
as hereinafter defined, and to pay on the Demand Redemption Date to the
Pollution Control Trustee, interest hereon from the Initial Interest Accrual
Date, as hereinafter defined, to the Demand Redemption Date at the same rate or
rates per annum then and thereafter from time to time borne by the Pollution
Control Revenue Refunding Bonds (Northern States Power Company - Sherburne
County Generating Station Units 1 and 2 Project), Series 2000-A (the "Pollution
Control Revenue Bonds"), in like money, said interest being payable at the
office of the Trustee in Chicago, Illinois, subject to the provisions
hereinafter set forth in the event of a rescission of a Redemption Demand, as
hereinafter defined.

         This bond is one of a duly authorized issue of bonds of the Company,
known as its First Mortgage Bonds, unlimited in aggregate principal amount,
which issue of bonds consists, or may consist of several series of varying
denominations, dates and tenors, all issued and to be issued under and equally
secured (except in so far 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 50 supplemental trust indentures
(the "Supplemental Indentures"), 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 the Trustee. The 1937 Indenture, as supplemented by
the Supplemental Indentures, the Restated Indenture and the New Supplemental
Indenture, is referred to as the "Indenture". Reference is hereby 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 provided.


                                       5

<PAGE>




         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/or the
holders of the bonds, and/or the terms and provisions of the Indenture and/or 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 bonds 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.

         This bond is one of a series of bonds of the Company issued under the
Indenture and designated as First Mortgage Bonds, Pollution Control Series S.
The bonds of this Series have been issued to the Pollution Control Trustee under
the Pollution Control Indenture to secure payment of the Pollution Control
Revenue Bonds issued by the City under the Pollution Control Indenture, the
proceeds of which have been or are to be loaned to the Company pursuant to the
provisions of the Loan Agreement dated as of March 1, 2000 (the "Agreement")
between the Company and the City. The maturity of the obligation represented by
the bonds of this Series is April 1, 2030. The date of maturity of the
obligation represented by the bonds of this Series is hereinafter referred to as
the Final Maturity Date. The bonds of this Series shall bear interest from the
Initial Interest Accrual Date, as hereinafter defined, at the same rate or rates
per annum then and thereafter from time to time borne by the Pollution Control
Revenue Bonds.

         Except as provided in the next succeeding paragraph, in the event of a
default under Section 8.01 of the Agreement or in the event of a default in the
payment of the principal of, premium, if any, or interest (and such default in
the payment of interest continues for the full grace period, if any, permitted
by the Pollution Control Indenture and the Pollution Control Revenue Bonds) on
the Pollution Control Revenue Bonds, whether at maturity, by acceleration, by
sinking fund, redemption or otherwise, as and when the same becomes due, the
bonds of this Series shall be redeemable in whole upon receipt by the Trustee of
a written demand (hereinafter called a "Redemption Demand") from the Pollution
Control Trustee stating that there has been such a default, stating that it is
acting pursuant to the authorization granted by Section 8.03 of the Pollution
Control Indenture, specifying the last date to which interest on the Pollution
Control


                                       6

<PAGE>




Revenue Bonds has been paid (such date being hereinafter referred to as the
"Initial Interest Accrual Date") and demanding redemption of the bonds of this
Series. The Trustee shall, within 10 days after receiving such Redemption
Demand, mail a copy thereof to the Company 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 (hereinafter called 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 at least 30 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 120th day after receipt by the Trustee of the Redemption Demand or (ii) the
Final Maturity Date, provided that if the Trustee shall not have received such
notice fixing the Demand Redemption Date within 90 days after receipt by it of
the Redemption Demand, the Demand Redemption Date shall be deemed to be the
earlier of (i) the 120th day after receipt by the Trustee of the Redemption
Demand or (ii) the Final Maturity Date. The Trustee shall mail notice of the
Demand Redemption Date (such notice being hereafter called the "Demand
Redemption Notice") to the Pollution Control Trustee not more than 10 nor less
than five days prior to the Demand Redemption Date. Notwithstanding the
foregoing, if a default to which this paragraph is applicable is existing on the
Final Maturity Date, such date shall be deemed to be the Demand Redemption Date
without further action (including actions specified in this paragraph) by the
Pollution Control Trustee, 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 Pollution Control Trustee to the Trustee, at a redemption price
equal to the principal amount thereof, plus accrued interest thereon at the rate
per annum set forth in the first paragraph of this Bond, from the Initial
Interest Accrual Date to the Demand Redemption Date. If a Redemption Demand is
rescinded by the Pollution Control Trustee by written notice to the Trustee
prior to the Demand Redemption Date, no Demand Redemption Notice shall be given,
or, if already given, shall be automatically annulled, and interest on the bonds
of this Series shall cease to accrue, all interest accrued thereon shall be
automatically rescinded and cancelled and the Company shall not be obligated to
make any payments of principal of or interest on the bonds of this Series; but
no such rescission shall extend to or affect any subsequent default or impair
any right consequent thereon.

         In the event that all of the bonds outstanding under the Indenture
shall have become immediately due and payable, whether by declaration or
otherwise, and such acceleration shall not have been annulled, the bonds of this
Series shall bear interest at the rate per annum set forth in the first
paragraph of this Bond, from the Initial Interest Accrual Date, as specified in
a written notice to the Trustee from the Pollution Control Trustee, and the
principal of and interest on the bonds of this Series from the Initial Interest
Accrual Date shall be payable in accordance with the provisions of the
Indenture.

         Upon payment of the principal of and premium, if any, and interest on
the Pollution Control Revenue Bonds, whether at maturity or prior to maturity by
redemption or otherwise, and the surrender thereof to and cancellation thereof
by the Pollution Control Trustee (other than any Pollution Control Revenue Bond
that was cancelled by the Pollution Control Trustee and for which one or more
other Pollution Control Revenue Bonds were delivered and authenticated pursuant
to the Pollution Control Indenture in lieu of or in exchange or substitution for
such cancelled Pollution Control Revenue Bond), or upon provision for the
payment thereof having



                                       7

<PAGE>




been made in accordance with the Pollution Control Indenture, bonds of this
Series in a principal amount equal to the principal amount of the Pollution
Control Revenue Bonds so surrendered and cancelled or for the provision for
which payment has been made shall be deemed fully paid and the obligations of
the Company thereunder shall be terminated, and such bonds of this Series shall
be surrendered by the Pollution Control Trustee to the Trustee and shall be
cancelled by the Trustee.

         No recourse shall be had for the payment of, or interest, if any, on
this bond, or any part thereof, or of any claim based hereon or in respect
hereof or of the Indenture, against any incorporator, or any past, present or
future stockholder, 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.

         The 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.

         IN WITNESS WHEREOF, NORTHERN STATES POWER COMPANY has caused this
instrument 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.

Dated:                                      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 is desirous of conveying, assigning, transferring,
mortgaging, pledging, setting over, and confirming to the Trustee and to its
respective successors in trust,



                                       8
<PAGE>




additional property acquired by it subsequent to the date of the preparation of
the Supplemental Trust Indenture dated as of August 1, 2000; 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 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 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 BNY Midwest Trust Company, as 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. SPECIFIC SUBJECTION OF ADDITIONAL PROPERTY
                      TO THE LIEN OF THE ORIGINAL INDENTURE

         SECTION 1.01. The Company in order to better secure the payment, of
both 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 to the 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 to conform with the provisions of the
Uniform Commercial Code, all fossil, nuclear, hydro, and other electric
generating plants, including buildings and other structures, turbines,
generators, exciters, boilers, reactors, nuclear fuel, other boiler plant
equipment, condensing equipment and all other generating equipment; substations;
electric transmission and



                                       9

<PAGE>




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; telephone plant and related
distribution systems; trucks and trailers; office, shop, and other buildings and
structures, furniture and equipment; apparatus and equipment of all other kinds
and descriptions; materials and supplies; all municipal and other franchises,
leaseholds, licenses, permits, privileges, patents and patent rights; all shares
of stock, bonds, evidences of indebtedness, contracts, claims, accounts
receivable, choses in action and other intangibles, all books of account and
other corporate records;

         Excluding, however, all merchandise and appliances heretofore or
hereafter acquired for the purpose of sale to customers and others;

         All the estate, right, title, interest, and claim, whatsoever, at law
as well as in equity, which the Company now has or hereafter may acquire in and
to the aforesaid property and every part and parcel thereof subject, however, to
the right of the Company, until the happening of a completed default as defined
in Section 1 of Article XIII of the Original Indenture prior to the Effective
Date and upon the occurrence and continuation of a Completed Default as defined
in the Restated Indenture on and after the Effective Date, to retain in its
possession all shares of stock, notes, evidences of indebtedness, other
securities and cash not expressly required by the provisions hereof to be
deposited with the Trustee, to retain in its possession all contracts, bills and
accounts receivable, motor cars, any stock of goods, wares and merchandise,
equipment or supplies acquired for the purpose of consumption in the operation,
construction, or repair of any of the properties of the Company, and to sell,
exchange, pledge, hypothecate, or otherwise dispose of any or all of such
property so retained in its possession free from the lien of the Indenture,
without permission or hindrance on the part of the Trustee, or any of the
bondholders. No person in any dealings with the Company in respect of any such
property shall be charged with any notice or knowledge of any such completed
default (prior to the Effective Date) or Completed Default (after the Effective
Date) under the Indenture while the Company is in possession of such property.
Nothing contained herein or in the Indenture shall be deemed or construed to
require the deposit with, or delivery to, the Trustee of any of such property,
except such as is specifically required to be deposited with the Trustee by some
express provision of the Indenture;

         To have and to hold all said property, real, personal, and mixed,
granted, bargained; sold, warranted, released, conveyed, assigned, transferred,
mortgaged, pledged, set over, or confirmed by the Company as aforesaid, or
intended so to be, to the Trustee and its successors and assigns forever,
subject, however, to permitted liens as defined in Section 5 of Article I of the
1937 Indenture prior to the Effective Date and to Permitted Encumbrances on and
after the Effective Date 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.



                                       10

<PAGE>



         ARTICLE II. PROVISIONS OF BONDS OF POLLUTION CONTROL SERIES S

         SECTION 2.01. There is hereby created, for issuance under the
Indenture, a series of bonds designated Pollution Control Series S, each of
which shall bear the descriptive title "First Mortgage Bonds, Pollution Control
Series S" and the form thereof shall contain suitable provisions with respect to
the matters specified in this section. The Bonds of Pollution Control Series S
shall be printed, lithographed or typewritten and shall be substantially of the
tenor and purport previously recited. The Bonds of Pollution Control Series S
shall be issued as registered bonds without coupons in denominations of a
multiple of $5,000 and shall be registered in the name of the Pollution Control
Trustee. The Bonds of Pollution Control Series S shall be dated as of the date
of their authentication.

         The Bonds of Pollution Control Series S shall be payable, both as to
principal and interest, at the office of the Trustee in Chicago, Illinois, in
lawful money of the United States of America. The maturity of the obligation
represented by the Bonds of Pollution Control Series S is April 1, 2030. The
date of maturity of the obligation represented by the Bonds of Pollution Control
Series S is hereinafter referred to as the Series S Final Maturity Date. The
Bonds of Pollution Control Series S shall bear interest from the Series S
Initial Interest Accrual Date, as hereinafter defined, at the same rate or rates
then and thereafter from time to time borne by the Pollution Control Revenue
Bonds.

         SECTION 2.02. Except as provided in the next succeeding paragraph of
this Section 2.02, in the event of a default under Section 8.01 of the Agreement
or in the event of a default in the payment of the principal of, premium, if
any, or interest on the Pollution Control Revenue Bonds, whether at maturity, by
acceleration, by sinking fund, redemption or otherwise, as and when the same
becomes due, the Bonds of Pollution Control Series S shall be redeemable in
whole upon receipt by the Trustee of a written demand (hereinafter called a
"Series S Redemption Demand") from the Pollution Control Trustee stating that
there has been such a default, stating that it is acting pursuant to the
authorization granted by Section 8.03 of the Pollution Control Indenture,
specifying the last date to which interest on the Pollution Control Revenue
Bonds has been paid (such date being hereinafter referred to as the "Series S
Initial Interest Accrual Date") and demanding redemption of the Bonds of
Pollution Control Series S. The Trustee shall, within 10 days after receiving
such Series S Redemption Demand, mail a copy thereof to the Company marked to
indicate the date of its receipt by the Trustee. Promptly upon receipt by the
Company of such copy of a Series S Redemption Demand, the Company shall fix a
date on which it will redeem the Bonds of Pollution Control Series S so demanded
to be redeemed (hereinafter called the "Series S Demand Redemption Date").
Notice of the date fixed as the Series S Demand Redemption Date shall be mailed
by the Company to the Trustee at least 30 days prior to such Series S Demand
Redemption Date. The date to be fixed by the Company as and for the Series S
Demand Redemption Date may be any date up to and including the earlier of (i)
the 120th day after receipt by the Trustee of the Series S Redemption Demand or
(ii) the Series S Final Maturity Date; provided that if the Trustee shall not
have received such notice fixing the Series S Demand Redemption Date within 90
days after receipt by it of the Series S Redemption Demand, the Series S Demand
Redemption Date shall be deemed to be the earlier of (i) the 120th day after
receipt by the Trustee of the Series S Redemption Demand or (ii) the Series S
Final Maturity Date. The Trustee shall mail notice of the Series S Demand
Redemption Date (such notice being hereinafter called the "Series S Demand
Redemption Notice") to the


                                       11

<PAGE>




Pollution Control Trustee not more than 10 nor less than five days prior to
the Series S Demand Redemption Date. Notwithstanding the foregoing, if a default
to which this paragraph is applicable is existing on the Series S Final Maturity
Date, such date shall be deemed to be the Demand Redemption Date without further
action (including actions specified in this paragraph) by the Pollution Control
Trustee, the Trustee or the Company. The Bonds of Pollution Control Series S
shall be redeemed by the Company on the Series S Demand Redemption Date, upon
surrender thereof by the Pollution Control Trustee to the Trustee, at a
redemption price equal to the principal amount thereof, plus accrued interest
thereon at the rate per annum set forth in Section 2.01 hereof, from the Series
S Initial Interest Accrual Date to the Series S Demand Redemption Date. If a
Series S Redemption Demand is rescinded by the Pollution Control Trustee by
written notice to the Trustee prior to the Series S Demand Redemption Date, no
Series S Demand Redemption Notice shall be given, or, if already given, shall be
automatically annulled, and interest on the Bonds of Pollution Control Series S
shall cease to accrue, all interest accrued thereon shall be automatically
rescinded and cancelled and the Company shall not be obligated to make any
payments of principal of or interest on the Bonds of Pollution Control Series S;
but no such rescission shall extend to or affect any subsequent default or
impair any right consequent thereon.

         In the event that all of the bonds outstanding under the Indenture
shall have become immediately due and payable, whether by declaration or
otherwise, and such acceleration shall not have been annulled, the Bonds of
Pollution Control Series S shall bear interest at the rate per annum set forth
in Section 2.01 hereof; from the Series S Initial Interest Accrual Date, as
specified in a written notice to the Trustee from the Pollution Control Trustee,
and the principal of and interest on the Bonds of Pollution Control Series S
from the Series S Initial Interest Accrual Date shall be payable in accordance
with the provisions of the Indenture.

         Anything herein contained to the contrary notwithstanding, the Trustee
is not authorized to take any action pursuant to a Series S Redemption Demand or
a rescission thereof or a written notice required by this Section 2.02, and such
Series S Redemption Demand, rescission or notice shall be of no force or effect,
unless it is executed in the name of the Pollution Control Trustee by one of its
Vice Presidents.

         SECTION 2.03. Upon payment of the principal of and premium, if any, and
interest on the Pollution Control Revenue Bonds, whether at maturity or prior to
maturity by redemption or otherwise, and the surrender thereof to and
cancellation thereof by the Pollution Control Trustee (other than any Pollution
Control Revenue Bond that was cancelled by the Pollution Control Trustee and for
which one or more other Pollution Control Revenue Bonds were delivered and
authenticated pursuant to the Pollution Control Indenture), or upon provision
for the payment thereof having been made in accordance with the Pollution
Control Indenture, Bonds of Pollution Control Series S in a principal amount
equal to the principal amount of the Pollution Control Revenue Bonds so
surrendered and cancelled or for the provision for which payment has been made
shall be deemed fully paid and the obligations of the Company thereunder shall
be terminated, and such Bonds of Pollution Control Series S shall be surrendered
by the Pollution Control Trustee to the Trustee and shall be cancelled and
disposed of by the Trustee in accordance with its customary procedures, and a
certificate of such cancellation and destruction shall be delivered to the
Company.


                                       12

<PAGE>




         SECTION 2.04. The Pollution Control Trustee as the registered holder of
the Bonds of Pollution Control Series S, at its option may surrender the same at
the office of the Trustee, in Chicago, Illinois, or elsewhere, if authorized by
the Company, for cancellation, in exchange for other bonds of the same series of
the same aggregate principal amount. Thereupon, and upon receipt of any payment
required under the provisions of Section 2.05 hereof, the Company shall execute
and deliver to the Trustee and the Trustee shall authenticate and deliver such
other registered bonds to such registered holder at its office or at any other
place specified as aforesaid.

         SECTION 2.05. No charge shall be made by the Company for any exchange
or transfer of Bonds of Pollution Control Series S other than for taxes or other
governmental charges, if any that may be imposed in relation thereto.


  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. Reference to Article I hereof is made for a description
of the property of the debtor covered by this Financing Statement with the same
force and effect as if incorporated in this Section at length.

         SECTION 3.03. 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>                                                          <C>
                Series due April 1, 2003...................................   $ 80,000,000
                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
</TABLE>


                                       13

<PAGE>


<TABLE>
<S>             <C>                                                           <C>
                Pollution Control Series N.................................   $ 27,900,000
                Pollution Control Series O.................................   $ 50,000,000
                Pollution Control Series P.................................   $ 50,000,000
                Resource Recovery Series Q.................................   $ 15,170,000
                Resource Recovery Series R.................................   $ 19,615,000
                Series due March 1, 2003...................................   $100,000,000
                Series due March 1, 2028...................................   $150,000,000
                Series due August 15, 2003.................................   $308,000,000
                Pollution Control Series S.................................   $ 69,000,000
</TABLE>

         SECTION 3.04. This Financing Statement is hereby adopted for all of the
First Mortgage Bonds of the series mentioned above secured by said Indenture.

         SECTION 3.05. 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, 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


                                       14

<PAGE>



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

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



                                       15

<PAGE>



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

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 Indenture
     Dated May 1, 1988

Supplemental Indenture
     Dated July 1, 1989



                                       16
<PAGE>



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

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

         SECTION 3.06. The property covered by this Financing Statement also
shall secure additional series of First Mortgage Bonds of the debtor which may
be issued from time to time in the future in accordance with the provisions of
the Indenture.

                      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



                                       17

<PAGE>




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 Trust Indenture dated
May 1, 1985. Each holder or registered owner of a bond of any series (including
Bonds of Pollution Control Series S) 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 the value of any
of the property subject 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.

         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, 1998, May 1, 1999, June 1, 2000, August 1, 2000 and June 1,
2002.

         SECTION 5.03. (a) If any provision of 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
amended (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 provision shall control.

         (b) In case any one or more of the provisions contained in this
Supplemental Indenture or in the bonds issued hereunder shall 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.


                                       18

<PAGE>




         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
simultaneously executed 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 amount of obligations to be issued forthwith under the Indenture is
$69,000,000.

                          ----------------------------


                                       19
<PAGE>




         IN WITNESS WHEREOF, on this 15th day of August, A.D. 2002, 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 July 1, 2002, 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 July 1, 2002, to be signed by its President,
a Vice President, or an Assistant Vice President, and attested by its Secretary
or an Assistant Secretary, for and in its behalf.


                                        NORTHERN STATES POWER COMPANY


                                        ----------------------------------------
                                        By:  Paul E. Pender
                                             Its:  Vice President and Treasurer
Attest:



--------------------------------------
Nancy Haley
Assistant Secretary

Executed by Northern States
Power Company in the presence of:


--------------------------------------                          (CORPORATE SEAL)
Mary Schell, Witness


--------------------------------------
Elizabeth Blohm, Witness


<PAGE>




                                           BNY MIDWEST TRUST COMPANY,
                                           as Trustee


                                           -------------------------------------
                                           By: J. Bartolini
                                               Its: Vice President
Attest:



-------------------------------------
M. Callahan
Assistant Vice President


Executed by BNY Midwest Trust Company
in the presence of:


-------------------------------------                           (CORPORATE SEAL)
K. Gibson, Witness


-------------------------------------
A. Hernandez, Witness


<PAGE>




STATE OF MINNESOTA           )
                             )      ss.:
COUNTY OF HENNEPIN           )


         On this 15th day of August A.D. 2002, before me, Sharon Quellhorst, a
Notary Public in and for said County in the State aforesaid, personally appeared
Paul E. Pender, and Nancy Haley, to me personally known, and to me known to be
the 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 for himself, did say that he, the said Paul E. Pender is a Vice
President and Treasurer, and she, the said Nancy Haley is the 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 on behalf of said corporation
by authority of its stockholders and board of directors; and said Paul E. Pender
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 15th day of August, A.D. 2002.


                                                                   (NOTARY SEAL)
----------------------------------------
Sharon Quellhorst
Notary Public

My Commission Expires:  January 31, 2005



<PAGE>




STATE OF MINNESOTA           )
                             )      ss.:
COUNTY OF HENNEPIN           )


         Paul E. Pender and Nancy Haley, being severally duly sworn, each
deposes and says that he, the said Paul E. Pender 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
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.


---------------------------------        ---------------------------------------
Paul E. Pender                            Nancy Haley


         Subscribed and sworn to before me this 15th day of August, A.D. 2002.

                                                                   (NOTARY SEAL)
---------------------------------
Sharon Quellhorst
Notary Public

My Commission Expires:  January 31, 2005



<PAGE>




STATE OF ILLINOIS          )
                           )   ss.:
COUNTY OF COOK             )


         On this _____ day of _______________, A.D. 2002, before me, L. Garcia,
a Notary Public in and for said County in the State aforesaid, personally
appeared J. Bartolini and M. Callahan to me personally known, and to me known to
be the Vice President and Assistant Vice President, 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 M. Callahan, is the Assistant Vice President, 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 on behalf of said corporation by authority of its board of
directors; and said J. Bartolinli and M. Callahan 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 _____ day of _______________,
A.D. 2002.


                                                                   (NOTARY SEAL)
------------------------------------
L. Garcia
Notary Public

My Commission Expires:  July 8, 2006



<PAGE>




STATE OF ILLINOIS        )
                         )    ss.:
COUNTY OF COOK           )


         J. Bartolini and M. Callahan, being severally duly sworn, each for
himself deposes and says that she, the said J. Bartolini, is Vice President, and
she, the said M. Callahan, is Assistant Vice President, of BNY Midwest Trust
Company, the corporation described in and which executed the within and
foregoing Supplemental Trust Indenture, as mortgagee; and each for himself
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.

----------------------------------        --------------------------------------
J. Bartolini                              M. Callahan


         Subscribed and sworn to before me this __________ day of
_______________, A.D. 2002.


                                                                   (NOTARY SEAL)
---------------------------------
L. Garcia
Notary Public

My Commission Expires:  July 8, 2006




<PAGE>




                                   SCHEDULE A

         The property referred to in Article I of the foregoing Supplemental
Trust Indenture from Northern States Power Company to BNY Midwest Trust Company,
Trustee, made as of July 1, 2002 includes the following property hereinafter
more specifically described. Such description, however, is not intended to limit
or impair the scope or intention of the general description contained in the
granting clauses or elsewhere in the Original Indenture.

                     I. PROPERTIES IN THE STATE OF MINNESOTA

         The following described real property, situate, lying and being in the
County of Hennepin, to-wit:

         1.   Lot 1, Block 1, Ceridian 2nd Addition, according to the
              recorded plat thereof, Hennepin County, Minnesota.

              Together with and subject to the easements filed with the Hennepin
              County Recorder's Office as Document Nos. 3714541, 6584907 and
              6987085 to the extent such easements are appurtenant to the
              above-referenced real property.

                      II. TRANSMISSION LINES OF THE COMPANY

         The electric transmission lines of the Company, including towers,
poles, pole lines, wire, switch racks, switchboards, insulators, and other
appliances and equipment, and all other property forming a part thereof or
appertaining thereto, and all service lines extending therefrom; together with
all rights for or relating to the construction, maintenance of operation
thereof, through, over, under, or upon any private property of public streets or
highways within as well as without the corporate limits of any municipal
corporation, and particularly the following described lines, to-wit:

                            IN THE STATE OF MINNESOTA

<TABLE>
<S>                 <C>                   <C>
Line 0808           0.56 Miles (U.G.)     High Bridge-Rogers Lake-Airport-Bloomington-Wilson
                                          Hennepin Co., MN., Sec 36, T28N, R23W

Line 5531           14.91 Miles           Pipestone-Chanerambie
                                          Pipestone Co., MN., Sec 12, T106N, R46W
                                          Pipestone Co., MN., Sec's 4, 7, 8, 9, T106N, R45W
                                          Pipestone Co., MN., Sec's 33, 34, 35, 36, T107N, R45W
                                          Pipestone Co., MN., Sec's 31, 32, 33, 34, 35, 36, T107N, R44W
                                          Murray Co., MN., Sec 1, T106N, R43W
                                          Murray Co., MN., Sec 31, T105N, R43W

Line 0832           8.68 Miles            Black Dog-Burnsville-Lake Marion
                                          Waseca Co., MN., Sec 18, T107N, R22W
</TABLE>




                                      A-1
<PAGE>



<TABLE>
<S>                 <C>                   <C>
                                          Waseca Co., MN., Sec's 1, 12, 13, T107N, R23W
                                          Waseca Co., MN., Sec's 1, 12, 13, 24, 25, 36, T108 N, R23W

Line 0832           7.28 Miles            Black Dog-Burnsville-Lake Marion
                                          LeSueur Co., MN., Sec's 35, 36, T109N, R23W
                                          Rice Co., MN., Sec's 17, 20, 29, 30, T109N, R22W

Line 0703           6.62 Miles            Yankee Doodle-Northfield (Tap to Kegan Lake and Air Lake)
                                          Dakota Co., MN., Sec's 31, 32, 33, T114N, R20W
                                          Dakota Co., MN., Sec 36, T114N, R21W
                                          Scott Co., MN., Sec's 1, 12, 13, T113N, R21W
</TABLE>


                            -------------------------

         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.



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