
<PAGE>
                          SUPPLEMENTAL TRUST INDENTURE
                                      FROM
                         NORTHERN STATES POWER COMPANY
 
                                       TO
                         HARRIS TRUST AND SAVINGS BANK
                                    TRUSTEE
                                 --------------
                              DATED MARCH 1, 1998
                                 --------------
                        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>                                                                                    <C>
Parties....................................................................................................           1
Recitals...................................................................................................           1
Form of Bonds of Series 2028 Bonds and Series 2003 Bonds...................................................           2
Form of Trustee's Certificate..............................................................................           5
Further Recitals...........................................................................................           5
 
                                                       ARTICLE I.
                               SPECIFIC SUBJECTION OF ADDITIONAL PROPERTY TO THE LIEN OF
                                                THE ORIGINAL INDENTURE.
Section 1.01--        Grant of certain property, including personal property to comply with the Uniform
                      Commercial Code, subject to permitted liens and other exceptions contained in 1937
                      Indenture............................................................................           5
 
                                                      ARTICLE II.
                             FORM AND EXECUTION OF SERIES 2028 BONDS AND SERIES 2003 BONDS.
Section 2.01--        Terms of Series 2028 Bonds...........................................................           6
Section 2.02--        Terms of Series 2003 Bonds...........................................................           8
Section 2.03--        Redemption of Series 2028 Bonds and Series 2003 Bonds................................           9
Section 2.04--        Interchangeability of bonds..........................................................           9
Section 2.05--        Charges for exchange or transfer of bonds............................................           9
Section 2.06--        Execution of bonds...................................................................           9
Section 2.07--        Book-Entry System....................................................................          10
 
                                                      ARTICLE III.
                                          APPOINTMENT OF AUTHENTICATING AGENT.
Section 3.01--        Appointment of agent or agents.......................................................          12
Section 3.02--(a)     Qualification of agents..............................................................          12
            (b)       Continuation of agent upon merger or consolidation...................................          12
            (c)       Termination of successor agent.......................................................          12
            (d)       Compensation of agent................................................................          12
Section 3.03--        Form of alternate certificate of authentication......................................          13
Section 3.04--        Limit on location and number of agents...............................................          13
 
                                                      ARTICLE IV.
                                         FINANCING STATEMENT TO COMPLY WITH THE
                                                UNIFORM COMMERCIAL CODE.
Section 4.01--        Names and addresses of debtor and secured party......................................          13
Section 4.02--        Property subject to lien.............................................................          13
Section 4.03--        Maturity dates and principal amounts of obligations secured..........................          13
Section 4.04--        Financing Statement adopted for all First Mortgage Bonds listed in Section 4.03......          14
</TABLE>
<PAGE>
 
                                       ii
 
<TABLE>
<CAPTION>
                                                                                                                PAGE
                                                                                                                -----
<S>                   <C>                                                                                    <C>
Section 4.05--        Recording data for the 1937 Indenture and prior Supplemental Trust Indentures........          14
Section 4.06--        Financing Statement covers additional series of First Mortgage Bonds.................          15
 
                                                       ARTICLE V.
                                                AMENDMENTS TO INDENTURE.
 
Section 5.01--        Consent of holders of Bonds..........................................................          15
 
                                                      ARTICLE VI.
                                                     MISCELLANEOUS.
Section 6.01--        Recitals of fact, except as stated, are statements of the Company....................          15
Section 6.02--        Supplemental Trust Indenture to be construed as a part of the 1937 Indenture, as
                      supplemented.........................................................................          15
Section 6.03--(a)     Trust Indenture Act to control.......................................................          16
            (b)       Severability of conditions contained in Supplemental Trust Indenture and bonds.......          16
Section 6.04--        Word "Indenture" as used herein includes in its meaning the 1937 Indenture and all
                      indentures supplemental thereto......................................................          16
Section 6.05--        References to either party in Supplemental Trust Indenture include successors or
                      assigns..............................................................................          16
Section 6.06--(a)     Provision for execution in counterparts..............................................          16
            (b)       Table of Contents and descriptive headings of Articles not to affect meaning.........          16
                                                     --------------
 
Schedule A.................................................................................................         A-1
</TABLE>
<PAGE>
    SUPPLEMENTAL  TRUST INDENTURE, made as of the 1st day of March, 1998, by and
between NORTHERN STATES POWER COMPANY, 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 HARRIS TRUST AND SAVINGS BANK, 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,  as  Trustee  (the
"Trustee"), party of the second part;
 
WITNESSETH:
 
    WHEREAS,  the Company heretofore  has executed and  delivered to the Trustee
its Trust Indenture (the "1937 Indenture"), made as of February 1, 1937, whereby
the Company granted, bargained,  sold, warranted, released, conveyed,  assigned,
transferred,  mortgaged, pledged, set over, and confirmed to the Trustee, and to
its respective successors in trust, all property, real, personal, and mixed then
owned or thereafter acquired or to be acquired by the Company (except as therein
excepted from  the lien  thereof) and  subject  to the  rights reserved  by  the
Company  in and  by the  provisions of the  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 Company heretofore has executed and delivered to the Trustee  a
Supplemental  Trust  Indenture, made  as of  June 1,  1942, whereby  the 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 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 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)
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
January 1, 1973                 Series due February 1, 2003
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)
</TABLE>
<PAGE>
 
                                       2
 
<TABLE>
<CAPTION>
     DATE OF SUPPLEMENTAL
       TRUST INDENTURE                            DESIGNATION OF SERIES
------------------------------  ----------------------------------------------------------
<S>                             <C>
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
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, and December 1, 2005
February 1, 1994                Series due February 1, 1999
October 1, 1994                 Series due October 1, 2001
June 1, 1995                    Series due July 1, 2025
April 1, 1997                   Pollution Control Series M, N, O and P; 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 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, 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 desirous of providing for the creation of (a) a new
series of First Mortgage  Bonds to be designated  "First Mortgage Bonds,  Series
due  March 1,  2028" (the  "Series 2028 Bonds")  and (b)  a new  series of First
Mortgage Bonds to be designated "First Mortgage Bonds, Series due March 1, 2003"
(the "Series  2003 Bonds",  and collectively  with the  Series 2028  Bonds,  the
"Bonds"),  the Bonds  of each  series 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 Series 2028 Bonds and Series 2003 Bonds)
                         NORTHERN STATES POWER COMPANY
            (Incorporated under the laws of the State of Minnesota)
                              First Mortgage Bond
                              Series due March 1,
No. ______________                                              $ ______________
 
    Unless this certificate is presented by an authorized representative of  The
Depository Trust Company, a New York corporation, to the issuer or its agent for
registration of transfer, exchange or payment, and any
<PAGE>
                                       3
 
certificate issued is registered in the name of Cede & Co. or such other name as
requested  by an authorized representative of  The Depository Trust Company (and
any payment is made to Cede & Co. or to such other entity as is requested by  an
authorized representative of The Depository Trust Company), ANY TRANSFER, PLEDGE
OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL since
the registered owner hereof, Cede & Co., has an interest herein.
 
    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 to                 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,
the  sum of                    Dollars in  lawful money of  the United States of
America, on the first day  of March, [2028] [2003],  and to pay interest  hereon
from  the date hereof at the rate  of [six and one-half][five and seven-eighths]
percent per annum, in like money, until the Company's obligation with respect to
the payment  of such  principal sum  shall be  discharged; said  interest  being
payable  at the  option of the  person entitled  to such interest  either 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, on the first day of March
and on the first day of September in each year provided that as long as there is
no existing default in  the payment of  interest and except  for the payment  of
defaulted  interest, the interest payable on any  March 1 or September 1 will be
paid to  the person  in whose  name this  bond was  registered at  the close  of
business on the record date (the February 18 prior to such March 1 or the August
21  prior to such  September 1 unless  any such date  is not a  business day, in
which event it will be the next preceding business day).
 
    "EXCEPT UNDER THE  LIMITED CIRCUMSTANCES DESCRIBED  IN THE INDENTURE,  THESE
GLOBAL  BONDS MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITORY OR BY A
NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY, ANOTHER NOMINEE OF THE  DEPOSITORY,
A SUCCESSOR OF THE DEPOSITORY OR A NOMINEE OF SUCH SUCCESSOR."
 
    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   45   supplemental   trust   indentures   (collectively,  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 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 provided.
 
    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  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.
<PAGE>
                                       4
 
    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  prior to maturity, for any reason,
and are not subject to a sinking fund.
 
    This bond is transferable as prescribed  in 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 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 the  Series  due March  1,  [2028] [2003],  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 or the interest
on  this bond, or any part  thereof, or of any claim  based hereon or in respect
hereof or of said Indenture, against any incorporator, or any past, present,  or
future  shareholder, officer or director of the Company or of any predecessor or
successor corporation, either directly  or through the  Company, or through  any
such  predecessor or successor corporation, or through any receiver or a trustee
in bankruptcy, whether by virtue of any constitution, statute, or rule of law or
by the enforcement of any assessment or penalty or otherwise, all such liability
being, by the acceptance hereof and as  part of the consideration for the  issue
hereof, expressly waived and released, as more fully provided in the Indenture.
 
    This bond shall not be valid or become obligatory for any purpose unless and
until  the certificate of authentication hereon shall  have been signed by or on
behalf of Harris Trust and Savings Bank, as Trustee under the Indenture, or  its
successor thereunder.
 
    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: ____________________________       NORTHERN STATES POWER COMPANY
        Attest: ________________________  By ___________________________________
         _________ Secretary                       _________ President
 
                          (Form of Trustee's Certificate)
<PAGE>
                                       5
 
    This bond is one of the bonds of the Series designated thereon, described in
the within-mentioned Indenture.
 
                                          HARRIS TRUST AND SAVINGS BANK,
                                                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, additional property acquired by it subsequent to
the date of  the preparation of  the Supplemental Trust  Indenture dated  April,
1997; 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 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  Harris Trust  and Savings  Bank,  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,
<PAGE>
                                       6
 
nuclear fuel, other boiler plant  equipment, condensing equipment and all  other
generating   equipment;  substations;  electric  transmission  and  distribution
systems, including structures,  poles, towers,  fixtures, conduits,  insulators,
wires,  cables,  transformers,  services  and meters;  steam  heating  mains and
equipment; gas  transmission  and distribution  systems,  including  structures,
storage  facilities,  mains,  compressor stations,  purifier  stations, pressure
holders,  governors,  services,   and  meters;  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 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.
 
                                  ARTICLE II.
         FORM AND EXECUTION OF SERIES 2028 BONDS AND SERIES 2003 BONDS
 
    SECTION 2.01. There hereby is created,  for issuance under the Indenture,  a
series  of bonds designated Series  due March 1, 2028,  each of which shall bear
the descriptive  title "First  Mortgage Bond,  Series due  March 1,  2028"  (the
"Series  2028 Bonds"),  and the form  thereof shall  contain suitable provisions
with respect to  the matters hereafter  specified in this  Section. Series  2028
Bonds  shall be  substantially of  the tenor  and purport  hereinbefore recited.
Series 2028 Bonds shall mature March 1, 2028, and shall be issued as  registered
bonds  without coupons in denominations of a multiple of $1,000. The Series 2028
Bonds shall bear interest at the rate of 6 1/2% per annum payable  semi-annually
on  March 1 and September 1 of each  year, and the principal 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, in lawful money of the United States of America, and  the
interest  shall be payable in like money at the option of the person entitled to
such interest
<PAGE>
                                       7
 
either at said 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. Series 2028
Bonds,  shall  be dated  as  of the  interest  payment date  next  preceding the
authentication thereof  by the  Trustee except  that (i)  if any  bond shall  be
authenticated  before September 1, 1998, it shall  be dated as of March 1, 1998,
unless (iii) below is applicable, (ii) if  the Company shall at the time of  the
authentication  of a Series 2028 Bond, be  in default in the payment of interest
upon the Series 2028 Bonds, such Series 2028 Bond shall be dated as of the  date
of  the beginning of  the period for which  such interest is  so in default, and
(iii) as long as there is no existing default in the payment of interest on  the
Series  2028 Bonds, if  any Series 2028  Bond, shall be  authenticated after the
close of business on  any Record Date  but on or prior  to the interest  payment
date relating to such Record Date, it shall be dated as of such interest payment
date.
 
    As  long as there is  no existing default in the  payment of interest on the
Series 2028 Bonds, the person in whose name any Series 2028 Bond, is  registered
at the close of business on any Record Date with respect to any interest payment
date  shall be entitled to receive the interest payable on such interest payment
date notwithstanding  any  transfer  or  exchange  of  such  Series  2028  Bond,
subsequent  to the Record  Date and on  or prior to  such interest payment date,
except as and  to the extent  the Company shall  default in the  payment of  the
interest  due  on  such interest  payment  date,  in which  case  such defaulted
interest shall be paid  to the person  in whose name such  Series 2028 Bond,  is
registered  on a Special Record Date for  the payment of such defaulted interest
to be fixed  by the Trustee,  notice thereof  shall be given  to the  registered
holder  of any  Series 2028 Bond,  not less than  10 days prior  to such Special
Record Date,  or  may be  paid  at  any time  in  any other  lawful  manner  not
inconsistent  with  the requirements  of any  securities  exchange on  which the
Series 2028 Bonds may be listed, and upon such notice as may be required by such
exchange.
 
    The term "Record Date" as used  herein with respect to any interest  payment
date  (March 1 or September 1) shall mean  the February 18 prior to such March 1
or August 21  prior to such  September 1 unless  such February 18  or August  21
shall  not be a business  day, in which event "Record  Date" shall mean the next
preceding business day. The  term "business day" as  used herein shall mean  any
day  other than  a Saturday or  a Sunday or  a day  on which the  offices of the
Trustee in the City of Chicago,  Illinois, are closed pursuant to  authorization
of law.
 
    As  used in this Section 2.01, the term "default in the payment of interest"
means  failure  to  pay  interest  on  the  applicable  interest  payment   date
disregarding any period of grace permitted by the Indenture.
 
    The  "Special Record Date"  as used herein  shall be fixed  in the following
manner. The  Company  shall notify  the  Trustee in  writing  of the  amount  of
defaulted interest proposed to be paid on each Series 2028 Bond, and the date of
the  proposed payment, and at  the same time the  Company shall deposit with the
Trustee an amount of money equal to the aggregate amount proposed to be paid  in
respect  of such defaulted  interest or shall  make arrangements satisfactory to
the Trustee for such  deposit prior to  the date of  the proposed payment,  such
money when deposited to be held in trust for the benefit of the persons entitled
to  such  defaulted interest  as provided  in this  Section 2.01.  Thereupon the
Trustee shall  fix a  Special Record  Date  for the  payment of  such  defaulted
interest which shall be not more than 15 nor less than 10 days prior to the date
of  the proposed  payment and  not less than  10 days  after the  receipt by the
Trustee of the notice of the proposed payment. The Trustee shall promptly notify
the Company of such Special Record Date and,  in the name and at the expense  of
the  Company,  shall cause  notice  of the  proposed  payment of  such defaulted
interest and the Special Record Date therefor to be mailed, first class  postage
prepaid,  to each holder of the Series 2028  Bonds, at his address as it appears
in the bond register, not less than  10 days prior to such Special Record  Date.
Notice of the proposed payment of such defaulted interest and the Special Record
Date  therefor having been mailed as aforesaid, such defaulted interest shall be
paid to the persons in whose names the Series 2028 Bonds, are registered on such
Special Record  Date  and  shall  not  be  payable  pursuant  to  the  paragraph
immediately following in this Section 2.01.
 
    The  Company may make payment of any  defaulted interest in any other lawful
manner not  inconsistent with  the requirements  of any  securities exchange  on
which  the Series  2028 Bonds,  may be listed,  and upon  such notice  as may be
required by such  exchange, if,  after notice  is given  by the  Company to  the
Trustee  of the  proposed payment  pursuant to  this Section  2.01, such payment
shall be deemed practicable by the Trustee.
<PAGE>
                                       8
 
    SECTION 2.02. There hereby is created,  for issuance under the Indenture,  a
series  of bonds designated Series  due March 1, 2003,  each of which shall bear
the descriptive  title "First  Mortgage Bond,  Series due  March 1,  2003"  (the
"Series  2003 Bonds"),  and the form  thereof shall  contain suitable provisions
with respect to the matters hereafter specified in this Section. The Series 2003
Bonds shall be substantially of the tenor and purport hereinbefore recited.  The
Series  2003 Bonds shall mature March 1, 2003, and shall be issued as registered
bonds without coupons in denominations of a multiple of $1,000. The Series  2003
Bonds  shall bear interest at the rate of 5 7/8% per annum payable semi-annually
on March 1 and September 1 of each  year, and the principal 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, in lawful money of the United States of America, and the
interest shall be payable in like money at the option of the person entitled  to
such  interest either at said 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.  Series 2003 Bonds,  shall be dated  as of the  interest payment date next
preceding the authentication thereof by the Trustee except that (i) if any  bond
shall  be authenticated before September 1, 1998,  it shall be dated as of March
1, 1998, unless (iii) below is applicable, (ii) if the Company shall at the time
of the authentication of  a Series 2003  Bond, be in default  in the payment  of
interest  upon the Series 2003 Bonds, such Series 2003 Bond shall be dated as of
the date  of the  beginning of  the  period for  which such  interest is  so  in
default,  and (iii) as  long as there is  no existing default  in the payment of
interest  on  the  Series  2003  Bonds,  if  any  Series  2003  Bond,  shall  be
authenticated  after the close of business on any Record Date but on or prior to
the interest payment date relating to such Record Date, it shall be dated as  of
such interest payment date.
 
    As  long as there is  no existing default in the  payment of interest on the
Series 2003 Bonds, the person in whose name any Series 2003 Bond, is  registered
at the close of business on any Record Date with respect to any interest payment
date  shall be entitled to receive the interest payable on such interest payment
date notwithstanding  any  transfer  or  exchange  of  such  Series  2003  Bond,
subsequent  to the Record  Date and on  or prior to  such interest payment date,
except as and  to the extent  the Company shall  default in the  payment of  the
interest  due  on  such interest  payment  date,  in which  case  such defaulted
interest shall be paid  to the person  in whose name such  Series 2003 Bond,  is
registered  on a Special Record Date for  the payment of such defaulted interest
to be fixed  by the Trustee,  notice thereof  shall be given  to the  registered
holder  of any  Series 2003 Bond,  not less than  10 days prior  to such Special
Record Date,  or  may be  paid  at  any time  in  any other  lawful  manner  not
inconsistent  with  the requirements  of any  securities  exchange on  which the
Series 2003 Bonds may be listed, and upon such notice as may be required by such
exchange.
 
    The term "Record Date" as used  herein with respect to any interest  payment
date  (March 1 or September 1) shall mean  the February 18 prior to such March 1
or August 21  prior to such  September 1 unless  such February 18  or August  21
shall  not be a business  day, in which event "Record  Date" shall mean the next
preceding business day. The  term "business day" as  used herein shall mean  any
day  other than  a Saturday or  a Sunday or  a day  on which the  offices of the
Trustee in the City of Chicago,  Illinois, are closed pursuant to  authorization
of law.
 
    As  used in this Section 2.02, the term "default in the payment of interest"
means  failure  to  pay  interest  on  the  applicable  interest  payment   date
disregarding any period of grace permitted by the Indenture.
 
    The  "Special Record Date"  as used herein  shall be fixed  in the following
manner. The  Company  shall notify  the  Trustee in  writing  of the  amount  of
defaulted interest proposed to be paid on each Series 2003 Bond, and the date of
the  proposed payment, and at  the same time the  Company shall deposit with the
Trustee an amount of money equal to the aggregate amount proposed to be paid  in
respect  of such defaulted  interest or shall  make arrangements satisfactory to
the Trustee for such  deposit prior to  the date of  the proposed payment,  such
money when deposited to be held in trust for the benefit of the persons entitled
to  such  defaulted interest  as provided  in this  Section 2.02.  Thereupon the
Trustee shall  fix a  Special Record  Date  for the  payment of  such  defaulted
interest which shall be not more than 15 nor less than 10 days prior to the date
of  the proposed  payment and  not less than  10 days  after the  receipt by the
Trustee of the notice of the proposed payment. The Trustee shall promptly notify
the Company of such Special Record Date and,  in the name and at the expense  of
the  Company,  shall cause  notice  of the  proposed  payment of  such defaulted
interest and the Special Record Date therefor to be
<PAGE>
                                       9
 
mailed, first class postage prepaid, to each holder of the Series 2003 Bonds, at
his address as it appears in the bond  register, not less than 10 days prior  to
such  Special  Record Date.  Notice of  the proposed  payment of  such defaulted
interest and the Special Record Date  therefor having been mailed as  aforesaid,
such  defaulted interest shall be paid to  the persons in whose names the Series
2003 Bonds, are registered on such Special Record Date and shall not be  payable
pursuant to the paragraph immediately following in this Section 2.02.
 
    The  Company may make payment of any  defaulted interest in any other lawful
manner not  inconsistent with  the requirements  of any  securities exchange  on
which  the Series  2003 Bonds,  may be listed,  and upon  such notice  as may be
required by such  exchange, if,  after notice  is given  by the  Company to  the
Trustee  of the  proposed payment  pursuant to  this Section  2.02, such payment
shall be deemed practicable by the Trustee.
 
    SECTION 2.03.  The Series  2028 Bonds  and  the Series  2003 Bonds  are  not
redeemable  prior to maturity  for any reason  and are not  subject to a sinking
fund.
 
    SECTION 2.04. 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,
bearing interest from its date, and  upon receipt of any payment required  under
the  provisions of Section 2.05 hereof.  Thereupon the 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  2.05. 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  2.06. 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 in 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.
<PAGE>
                                       10
 
    SECTION  2.07. (a) Except as provided in  subsections (c) and (g) below, the
registered holder of  all of the  Series 2028  Bonds and the  Series 2003  Bonds
shall be The Depository Trust Company ("DTC") and such Bonds shall be registered
in  the name  of Cede &  Co., as  nominee for DTC.  Payment of  principal of and
interest on any  Bonds registered in  the name of  Cede & Co.  shall be made  by
transfer  of New  York Federal  or equivalent  immediately available  funds with
respect to the Bonds to the account of Cede & Co. on each such payment date  for
the  respective series of Bonds  at the address indicated for  Cede & Co. in the
bond register kept by the Trustee for the respective series of Bonds.
 
    (b) The Series 2028 Bonds and the Series 2003 Bonds shall each be  initially
issued  in  the  form  of  a  separate  single  authenticated  fully  registered
certificate in the aggregate principal amount  of the Series 2028 Bonds and  the
Series  2003 Bonds, respectively.  Upon initial issuance,  the ownership of such
Bonds shall be registered in the bond  register kept by the Trustee in the  name
of  Cede & Co., as nominee of DTC. The Trustee and the Company may treat DTC (or
its nominee) as  the sole  and exclusive registered  holder of  the Series  2028
Bonds  and the Series 2003  Bonds, respectively, registered in  its name for the
purposes of payment of the  principal of and interest  on the Series 2028  Bonds
and  Series  2003 Bonds,  respectively, and  of giving  any notice  permitted or
required to  be given  to holders  under the  Indenture, except  as provided  in
Section 2.07(g) below; and neither the Trustee nor the Company shall be affected
by  any notice to the  contrary. Neither the Trustee  nor the Company shall have
any  responsibility  or  obligation  to  any  of  DTC's  participants  (each   a
"Participant"),  any person claiming a beneficial  ownership in the Bonds, under
or through DTC  or any  Participant (each a  "Beneficial Owner"),  or any  other
person  which is  not shown on  the bond  register maintained by  the Trustee as
being a  registered  holder,  with  respect  to  the  accuracy  of  any  records
maintained  by DTC or any Participant; the  payment of DTC or any Participant of
any amount in respect of the principal  of or interest on the Series 2028  Bonds
or  the Series 2003 Bonds, as the case  may be; any notice which is permitted or
required to be given  to registered holders under  the Indenture of Series  2028
Bonds  or the Series  2003 Bonds, as  the case may  be; or any  consent given or
other action taken by DTC as bondholder. The Trustee shall pay all principal  of
and  interest on the Bonds registered in the name of Cede & Co. only to or "upon
the order  of" DTC  (as that  term is  used in  the Uniform  Commercial Code  as
adopted  in Minnesota and  New York), and  all such payments  shall be valid and
effective to fully satisfy and discharge the Company's obligations with  respect
to  the principal of and  interest on such Series 2028  Bonds or the Series 2003
Bonds, as the case may be, to the extent  of the sum or sums so paid. Except  as
otherwise  provided in Sections 2.07(c) and (g)  below, no person other than DTC
shall receive authenticated bond certificates  evidencing the obligation of  the
Company  to make payments of principal of  and interest on the Series 2028 Bonds
or the Series  2003 Bonds,  as the  case may  be. Upon  delivery by  DTC to  the
Trustee  of written notice to the effect that DTC has determined to substitute a
new nominee  in place  of Cede  &  Co., and  subject to  the provisions  of  the
Indenture  with respect  to transfers of  bonds, the  word "Cede &  Co." in this
Supplemental Trust Indenture shall refer to such new nominee of DTC.
 
    (c) If the  Company in  its discretion  determines that  it is  in the  best
interest of the Beneficial Owners that they be able to obtain bond certificates,
the  Company  may notify  DTC and  the  Trustee, whereupon  DTC will  notify the
Participants of  the availability  through  DTC of  bond certificates.  In  such
event,  the  Trustee  shall issue,  transfer  and exchange  bond  certificate as
requested by  DTC in  appropriate amounts  pursuant to  Article II  of the  1937
Indenture  prior to the Effective Date, Article  II of the Restated Indenture on
and after  the  Effective Date  and  Section  2.04 of  this  Supplemental  Trust
Indenture.  The Company shall pay all costs in connection with the production of
bond certificates if the Company makes  such a determination under this  Section
2.07(c). DTC may determine to discontinue providing its services with respect to
the  Series 2028 Bonds  or the Series 2003  Bonds at any  time by giving written
notice to the Company and the Trustee and discharging its responsibilities  with
respect  thereto under applicable law. Under  such circumstances (if there is no
successor book-entry depository), the Company and the Trustee shall be obligated
(at the sole cost and expense of  the Company) to deliver bond certificates  for
such Series 2028 Bonds or Series 2003 Bonds, as the case may be, as described in
this  Supplemental  Trust  Indenture.  If  bond  certificates  are  issued,  the
provisions of the Indenture shall apply to, among other things, the transfer and
exchange of such  certificates and the  method of payment  and principal of  and
interest on such certificates. Whenever DTC requests the Company and the Trustee
to  do so, the Company will direct the  Trustee (at the sole cost and expense of
the Company) to cooperate with DTC in taking appropriate action after reasonable
notice (1) to make  available one or more  separate certificates evidencing  the
<PAGE>
                                       11
 
Series  2028  Bonds  or the  Series  2003 Bonds,  as  the  case may  be,  to any
Participant or  (2) to  arrange for  another book-entry  depository to  maintain
custody  of certificates  evidencing the  Series 2028  Bonds or  the Series 2003
Bonds, as the case may  be, registered in the name  of Cede & Co. Any  successor
book-entry  depository must be a clearing  agency registered with the Securities
and Exchange Commission pursuant to Section  17A of the Securities Exchange  Act
of  1934  and must  enter into  an agreement  with the  Company and  the Trustee
agreeing to act as the depository and clearing agency for the Series 2028  Bonds
or  the Series 2003  Bonds, as the case  may be, (except  as provided in Section
2.07(g) below). After such agreement has become effective, DTC shall present the
Series 2028 Bonds or the Series 2003 Bonds, as the case may be, for registration
of transfer in accordance with  Section 12 of Article  II of the 1937  Indenture
prior  to the Effective Date  and Section 2.12 of  the Restated Indenture on and
after the Effective Date, and the Trustee shall register them in the name of the
successor book-entry  depository  or  its nominee.  If  a  successor  book-entry
depository  has not  accepted such position  before the effective  date of DTC's
termination of its services, the book-entry system shall automatically terminate
and may not be reinstated without the  consent of all registered holders of  the
Series 2028 Bonds or the Series 2003 Bonds, as the case may be.
 
    (d) Notwithstanding any other provision of this Supplemental Trust Indenture
to  the contrary, so long as any Series 2028 Bonds are registered in the name of
Cede & Co., as nominee of DTC, all payments with respect to the principal of and
interest on such Series 2028 Bonds and  all notices with respect to such  Series
2028  Bonds shall  be made and  given, respectively,  to DTC as  provided in the
representation letter dated as of the date of delivery of the Series 2028  Bonds
among  DTC, the Company  and the Trustee.  The Trustee is  hereby authorized and
directed to comply with all terms of the representation letter.
 
    Notwithstanding any other provision of this Supplemental Trust Indenture  to
the  contrary, so long  as any Series 2003  Bonds are registered  in the name of
Cede & Co., as nominee of DTC, all payments with respect to the principal of and
interest on such Series 2003 Bonds and  all notices with respect to such  Series
2003  Bonds shall  be made and  given, respectively,  to DTC as  provided in the
representation letter dated as of the date of delivery of the Series 2003  Bonds
among  DTC, the Company  and the Trustee.  The Trustee is  hereby authorized and
directed to comply with all terms of the representation letter.
 
    (e) In connection  with any  notice or  other communication  to be  provided
pursuant  to the Indenture for the Series 2028 Bonds or the Series 2003 Bonds by
the Company or the  Trustee with respect  to any consent or  other action to  be
taken  by the  registered holders of  the Series  2028 Bonds or  the Series 2003
Bonds, the Company or the Trustee, as the case may be, shall seek to establish a
record date to the extent permitted by  the Indenture for such consent or  other
action  and  give DTC  notice of  such record  date not  less than  fifteen (15)
calendar days in advance of such record date to the extent possible. Such notice
to DTC shall be given only when DTC is the sole registered holder.
 
    (f) NEITHER THE  COMPANY NOR  THE TRUSTEE  WILL HAVE  ANY RESPONSIBILITY  OR
OBLIGATIONS TO THE PARTICIPANTS OR THE BENEFICIAL OWNERS WITH RESPECT TO (1) THE
ACCURACY OF ANY RECORDS MAINTAINED BY DTC OR ANY PARTICIPANT; (2) THE PAYMENT BY
DTC  OR ANY PARTICIPANT OF ANY AMOUNT DUE  TO ANY BENEFICIAL OWNER IN RESPECT OF
THE PRINCIPAL  OF OR  INTEREST ON  THE BONDS;  (3) THE  DELIVERY BY  DTC OR  ANY
PARTICIPANT OF ANY NOTICE TO ANY BENEFICIAL OWNER WHICH IS REQUIRED OR PERMITTED
UNDER  THE TERMS OF THE INDENTURE TO BE  GIVEN TO REGISTERED HOLDERS; OR (4) ANY
CONSENT GIVEN OR OTHER ACTION TAKEN BY DTC AS A REGISTERED HOLDER.
 
    SO LONG AS CEDE & CO. IS THE  REGISTERED HOLDER OF THE SERIES 2028 BONDS  AS
NOMINEE  OF DTC,  REFERENCES HEREIN TO  REGISTERED HOLDERS OF  SERIES 2028 BONDS
SHALL MEAN  CEDE  &  CO.  AND  SHALL NOT  MEAN  THE  BENEFICIAL  OWNERS  OF  THE
SERIES 2028 BONDS NOR DTC PARTICIPANTS.
 
    SO  LONG AS CEDE & CO. IS THE  REGISTERED HOLDER OF THE SERIES 2003 BONDS AS
NOMINEE OF DTC,  REFERENCES HEREIN TO  REGISTERED HOLDERS OF  SERIES 2003  BONDS
SHALL  MEAN  CEDE  &  CO.  AND  SHALL NOT  MEAN  THE  BENEFICIAL  OWNERS  OF THE
SERIES 2003 BONDS NOR DTC PARTICIPANTS.
<PAGE>
                                       12
 
    (g) The Company, in its sole  discretion, may terminate the services of  DTC
with  respect to the Series  2028 Bonds and/or Series  2003 Bonds if the Company
determines that:  (i)  DTC is  unable  to discharge  its  responsibilities  with
respect to the such Bonds; or (ii) a continuation of the requirement that all of
the outstanding Series 2028 Bonds or Series 2003 Bonds, as the case may be, must
be  registered with the  registration books kept  by the Trustee  in the name of
Cede & Co., as  nominee of DTC, is  not in the best  interest of the  Beneficial
Owners  of the Series 2028 Bonds or Series 2003 Bonds, as the case may be. After
such event  and if  no  substitute book-entry  depository  is appointed  by  the
Company, bond certificates will be delivered as described in the Indenture.
 
    (h)  Upon the termination of the services  of DTC with respect to the Series
2028 Bonds and/or the Series  2003 Bonds pursuant to  subsections (c) or (g)  of
this  Section 2.07 after which no substitute book-entry depository is appointed,
the Series  2028 Bonds  or Series  2003  Bonds, as  the case  may be,  shall  be
registered  in whatever name or names  holders transferring or exchanging Series
2028 Bonds  or  Series 2003  Bonds,  as the  case  may be,  shall  designate  in
accordance with the provisions of the Indenture.
 
                                  ARTICLE III.
                      APPOINTMENT OF AUTHENTICATING AGENT.
 
    SECTION  3.01. 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 3.02. (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  3.02
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.
 
    (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 3.02,  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 3.02.
 
    (d)  The  Trustee agrees to  pay to any  authenticating agent, appointed  in
accordance with the provisions of this Section 3.02, reasonable compensation for
its  services,  and the  Trustee shall  be  entitled to  be reimbursed  for such
payments.
<PAGE>
                                       13
 
    SECTION  3.03. If an appointment  is made pursuant to  this Article III, 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.
                                              HARRIS TRUST AND SAVINGS BANK,
                                                                   as Trustee,
 
                                          By
                                                  Authenticating Agent,
 
                                          By
                                                   Authorized Officer.
 
    SECTION  3.04. No provision of this Article III 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.
 
                                  ARTICLE IV.
        FINANCING STATEMENT TO COMPLY WITH THE UNIFORM COMMERCIAL CODE.
 
    SECTION  4.01. 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: Harris Trust and Savings Bank, Trustee
                       111 West Monroe Street
                       Chicago, Illinois 60603
 
    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 4.02. 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 4.03.  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>
Series due February 1, 1999.................................................   $  200,000,000
Series due October 1, 2001..................................................   $  150,000,000
Series due December 1, 2000.................................................   $  100,000,000
Series due March 1, 2002....................................................   $   50,000,000
Series due February 1, 2003.................................................   $   50,000,000
Series due April 1, 2003....................................................   $   80,000,000
Series due December 1, 2005.................................................   $   70,000,000
Resource Recovery Series I..................................................   $   18,400,000
Pollution Control Series J..................................................   $    5,450,000
Pollution Control Series K..................................................   $    3,400,000
</TABLE>
<PAGE>
 
                                       14
 
<TABLE>
<CAPTION>
FIRST MORTGAGE BONDS                                                          PRINCIPAL AMOUNT
----------------------------------------------------------------------------  ----------------
<S>                                                                           <C>
Pollution Control Series L..................................................   $    4,850,000
Series due July 1, 2025.....................................................   $  250,000,000
Pollution Control Series M..................................................   $   60,000,000
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
Series due March 1, 2003....................................................   $  100,000,000
</TABLE>
 
    SECTION 4.04. This  financing Statement  is hereby  adopted for  all of  the
First Mortgage Bonds of the series mentioned above secured by said Indenture.
 
    SECTION   4.05.  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
 
    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
 
    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
<PAGE>
                                       15
 
    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
 
    SECTION  4.06. 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 V.
                            AMENDMENTS TO INDENTURE.
 
    SECTION 5.01.  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 Series  2028 Bonds and the Series 2003  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 VI.
                                 MISCELLANEOUS.
 
    SECTION  6.01.  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.
 
    SECTION  6.02.  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,
<PAGE>
                                       16
 
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 and March 1, 1997.
 
    SECTION  6.03. (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
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  6.04.  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 6.05. 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  6.06.  (a)  This  Supplemental  Trust  Indenture  may  be  executed
simultaneously in several counter-
parts,  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
$250,000,000.
                                 --------------
<PAGE>
                                       17
 
    IN  WITNESS WHEREOF, on this  10th day of March,  A.D. 1998, 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  March  1,  1998, 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 HARRIS  TRUST AND  SAVINGS BANK,  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 March  1, 1998, 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.
 
<TABLE>
<S>                                       <C>
                                          NORTHERN STATES POWER COMPANY,
 
                                          BY EDWARD J. MCINTYRE, VICE PRESIDENT
 
Attest:
 
SUTTON A. PLOMBON, ASSISTANT SECRETARY.
 
Executed by Northern States
Power Company in presence of:
 
                                                                (CORPORATE SEAL)
 
MARY SCHELL, WITNESS
 
KEN BODELL, WITNESS                               HARRIS TRUST AND SAVINGS BANK,
                                                                      as Trustee
 
                                          BY K. HEALEY, VICE PRESIDENT
 
Attest:
 
D. G. DONOVAN, ASSISTANT SECRETARY.
 
Executed by Harris Trust and Savings
Bank in presence of:
 
                                                                (CORPORATE SEAL)
 
J. KINNEY, WITNESS
 
R. JOHNSON, WITNESS
</TABLE>
<PAGE>
                                       18
 
<TABLE>
<S>                   <C>
STATE OF MINNESOTA
COUNTY OF HENNEPIN    ss.:
</TABLE>
 
    On  this 10th day of March, A.D.  1998, before me, FAYE WAHLSTRAND, a Notary
Public in and for said County in the State aforesaid, personally appeared EDWARD
J. MCINTYRE and SUTTON A. PLOMBON, to me personally known, and to me known to be
Vice President 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 EDWARD J. MCINTYRE is Vice President, and she, the said SUTTON
A.  PLOMBON, 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
EDWARD J. MCINTYRE and SUTTON A. PLOMBON 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 10th day of March, A.D. 1998.
 
FAYE WAHLSTRAND
NOTARY PUBLIC, HENNEPIN COUNTY, MINN.
MY COMMISSION EXPIRES JANUARY 31, 2000
 
                        (NOTARIAL SEAL)
 
<TABLE>
<S>                   <C>
STATE OF MINNESOTA
COUNTY OF HENNEPIN    ss.:
</TABLE>
 
    EDWARD J. MCINTYRE and SUTTON A.  PLOMBON, being severally duly sworn,  each
deposes  and says that he,  the said EDWARD J.  MCINTYRE, is Vice President, and
she, the said  SUTTON A.  PLOMBON, 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.
 
    Subscribed and sworn to before me this 10th day of March, A.D. 1998.
 
FAYE WAHLSTRAND
NOTARY PUBLIC, HENNEPIN COUNTY, MINN.
MY COMMISSION EXPIRES JANUARY 31, 2000
 
                        (NOTARIAL SEAL)
<PAGE>
                                       19
 
<TABLE>
<S>                <C>
STATE OF ILLINOIS
COUNTY OF COOK     ss.:
</TABLE>
 
    On  this 10th  day of March,  A.D. 1998,  before me, M.  TINERELLA, a Notary
Public in and  for said County  in the State  aforesaid, personally appeared  K.
HEALEY  and D.G.  DONOVAN, to me  personally known, and  to me known  to be Vice
President and Assistant  Secretary, respectively,  of Harris  Trust and  Savings
Bank,  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 K. HEALEY, is Vice  President, and he, the said D.G. DONOVAN,
is Assistant Secretary, of  said Harris Trust and  Savings Bank, 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 K. HEALEY and
D.G. DONOVAN 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 10th day of March, A.D. 1998.
 
                                          M. TINERELLA
                                          NOTARY PUBLIC, COOK COUNTY, ILLINOIS.
                                          MY COMMISSION EXPIRES MAY 21, 2001
 
(NOTARIAL SEAL)
 
<TABLE>
<S>                <C>
STATE OF ILLINOIS
COUNTY OF COOK     ss.:
</TABLE>
 
    K.  HEALEY and  D.G. DONOVAN, being  severally duly sworn,  each for himself
deposes and says that  he, the said  K. HEALEY, is Vice  President, and he,  the
said D.G. DONOVAN, is Assistant Secretary, of Harris Trust and Savings Bank, 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 mortgagor.
 
    Subscribed and sworn to before me this 10th day of March, A.D. 1998.
 
K. HEALEY
D.G. DONOVAN
 
                                          M. TINERELLA
                                          NOTARY PUBLIC, COOK COUNTY, ILLINOIS.
                                          MY COMMISSION EXPIRES MAY 21, 2001
 
(NOTARIAL SEAL)
<PAGE>
                                      A-1
 
                                   SCHEDULE A
 
    The property referred to  in Article I of  the foregoing Supplemental  Trust
Indenture  from Northern States Power Company  to Harris Trust and Savings Bank,
Trustee, made as of March 1,  1998, 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 Chisago, to-wit:
 
    1. That  part of the  Northwest Quarter of the  Northwest Quarter of Section
       29, Township 33 North, Range 21 West, described as follows: Beginning  at
       the  Northwest corner of Section 29;  thence East (assumed bearing) along
       the North line of said Section 29 a distance of 279.40 feet; thence South
       26 degrees 56 minutes  East, a distance of  518.27 feet; thence North  63
       degrees 11 minutes East a distance of 35.00 feet; thence South 26 degrees
       56  minutes East  a distance  of 14.00 feet;  thence South  63 degrees 11
       minutes West a distance of 611.07 feet  to the West line of said  Section
       29;  thence North 00  degrees 29 minutes  50 seconds West  along the said
       West line a distance of 734.45 feet to the point of beginning.
 
    The following  described real  property,  situate, lying  and being  in  the
County of Hennepin, to-wit:
 
    1. Lot 32 and the Easterly 17.4 feet of Lot 33 Koehler's Addition to Mound.
 
    The  following  described real  property, situate,  lying  and being  in the
County of Washington, to-wit:
 
    1. Lots Five (5), Six (6), Seven (7), Eight (8), Nine (9), Ten (10),  Eleven
       (11) and Twelve (12), Block Eleven (11), of OAK PARK.
 
    2. Lots One (1), Two (2), Three (3), Four (4), Thirteen (13), Fourteen (14),
       Fifteen (15), and Sixteen (16), Block Eleven (11), OAK PARK.
 
    3. Lots  Five (5), Six (6), Seven (7), and Eight (8), Block Twelve (12), OAK
       PARK.
 
                   II.  GAS DISTRIBUTION LINES OF THE COMPANY
                           IN THE STATE OF MINNESOTA
 
    1. Approximately 2,000 feet of 6" diameter, and approximately 7,000 feet  of
       4" diameter high pressure gas main, constructed in 1997 in Ramsey County,
       known  as the 'Highway  10 Line', serving  a portion of  the community of
       Blaine in Anoka County, Minnesota.
<PAGE>
                                      A-2
 
                                 --------------
 
                         MORTGAGOR'S RECEIPT FOR COPY.
 
    The undersigned Northern  States Power Company,  the Mortgagor described  in
the foregoing Mortgage, hereby acknowledges that at the time of the execution of
the  Mortgage, Harris Trust  and Savings Bank,  Trustee, the Mortgagee described
therein, surrendered to  it a  full, true, complete,  and correct  copy of  said
instrument, with signatures, witnesses, and acknowledgments thereon shown.
 
                                              NORTHERN STATES POWER COMPANY.
 
                                          BY EDWARD J. MCINTYRE, VICE PRESIDENT
 
Attest:
 
SUTTON A. PLOMBON, ASSISTANT SECRETARY
 
                                 --------------
 
    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.
