SIXTEENTH SUPPLEMENTAL INDENTURE Dated as of November 15, 2012

by an amended and restated master trust indenture dated as of April 28, 2003 between the Issuer, the General Partner and the Trustee (the “Master Indenture”) provision was made for the issuance and securing of Bonds of the Issuer in one or more Series, unlimited as to aggregate principal mount but issuable only upon the terms and subject to the conditions therein provided;

the Issuer has duly authorized the creation and issue of Obligation Bonds, in the form of Medium-Term Notes (the “Notes”), pursuant to the provisions of the Master Indenture and this Supplemental Indenture;

the Issuer wishes to apply the net proceeds of the issue of Notes in accordance with the terms of Section 2.11 hereof;

this supplemental indenture is executed pursuant to all necessary authorizations and resolutions of the Issuer to authorize the creation, issuance and delivery of the Notes and to establish the terms, provisions and conditions thereof;

this supplemental indenture is hereinafter sometimes referred to as the “Sixteenth Supplemental Indenture”; and

the foregoing recitals are made as representations and statements of fact by the Issuer and not the Trustee.

The definition of “Business Day” in section 1.1 of the Master Indenture is replaced by the following definition:

The following additional words and phrases shall have the following meanings:

Date and Interest. Each Note shall be dated as of the date of issue and shall bear interest, if any, from the date of issue at the rate (either fixed ·or floating) determined by the Issuer at the time of issue, as specified in the Pricing Supplement for such Note. Interest, if any, shall be payable on the dates determined by the Issuer at the time of issue, as specified in the Pricing Supplement for such Note.

Maturity. Each Note shall mature on the date determined by the Issuer at the time of issue, as specified in the Pricing Supplement for such Note, which date shall be more than one year from the date of issue, as specified in the Pricing Supplement for such Note.

Currency. Each Note shall be issued and payable in such currency as is determined by the Issuer at the time of issue as specified in the Pricing Supplement for such Note.

Denominations. The Notes shall be issued in denominations of $1,000 or more in Canadian currency or the equivalent thereof in other currencies at the time of issue or in such other denominations as are determined by the Issuer at the time of issue as specified in the Pricing Supplement for such Notes.

The following terms and conditions shall apply to the determination of interest on a Note unless otherwise provided in the Note:

The Issuer will pay interest on a Note on each Interest Payment Date, commencing on the first Interest Payment Date next succeeding the Original Issue Date, and on the Stated Maturity or any prior date on which the principal, or an instalment of principal, of such Note becomes due or payable (the Stated Maturity or such prior date, as the case may be, is herein referred to as the "Maturity Date"); provided, however, that if the Original Issue Date falls between a Record Date and the related Interest Payment Date or on an Interest Payment Date, interest payments will commence on the second Interest Payment Date succeeding the Original Issue Date. Interest on such Note will accrue from and including the immediately preceding Interest Payment Date in respect of which interest has been paid or duly made available for payment or, if no interest has been paid, from and including the Original Issue Date, to but excluding such Interest Payment Date or the Maturity Date, as the case may be. If any Interest Payment Date or the Maturity Date falls on a day that is not a Business Day, the required payment of principal, premium, if any, and/or interest will be made on the next succeeding Business Day as if made on the date such payment was due, and no interest shall accrue on such

Payments of principal of, and premium, if any, and interest on, a Note will be made to the Holder thereof in Canadian dollars regardless of the Specified Currency stated therein unless the Holder thereof makes the election described below. If the Specified Currency is other than Canadian dollars, the Exchange Rate Agent will convert all payments in respect thereof into Canadian dollars in the manner described below; provided, however, that the Holder may elect to receive payment of principal of and premium, if any, and/or interest on such note in the Specified Currency by submitting a written request for such payment to the Trustee at its principal office in the City of Toronto on or prior to the applicable Record Date or at least 15 calendar days prior to the Maturity Date, as the case may be. Such written request may be mailed or hand delivered or sent by cable, telex or other form of facsimile transmission. The Holder may elect to receive payment in such Specified Currency for all such principal, premium, if any, and interest payments and need not file a separate election for each payment. The election will remain in effect until revoked by written notice to the Trustee, but written notice of any such revocation must be received by the Trustee on or prior to the applicable Record Date or at least 15 calendar days prior to the Maturity Date, as the case may be. Notwithstanding the foregoing, if the applicable Specified Currency is not available for the payment of principal, premium, if any, or interest with respect to such note due to the imposition of exchange controls or other circumstances beyond the control of the Issuer, the Issuer will be entitled to satisfy its obligations to the Holder by making such payment in Canadian dollars on the basis of the Market Exchange Rate on the second Business Day prior to such payment or, if such Market Exchange Rate is not then available, on the basis of the most recently available Market Exchange Rate. Any payment made in Canadian dollars under the circumstances set forth above where the required payment is in a Specified Currency other than Canadian dollars will not constitute a payment default under such Note or under the Master Indenture. All determinations referred to above made by the Issuer or its agent (including the Exchange Rate Agent) shall be at its sole discretion and shall, in the absence of manifest error, be conclusive and for all purposes binding on the Holder of such of a Note.

Interest payments for a Note shall be computed and paid on the basis of: (i) a 360-day year of twelve 30-day months if the Day Count Convention specified therein is “30/360” for the relevant period, (ii) the actual number of days in the related month and a 360-day year if the Day Count

For the purpose only of disclosure required by the Interest Act (Canada) and without affecting the interest payable on a Note, the yearly rate of interest which is equivalent to the rate of interest payable on a Note where the Day Count Convention specified above is other than “Actual/ Actual” is the rate of interest payable with respect to the Note multiplied by the number of days in the year for which such calculation is made and divided by 360.

The following terms and conditions shall apply to the determination of interest on a Floating Rate Note unless otherwise provided in the Floating Rate Note:

A Floating Rate Note shall bear interest at the rate determined by reference to the applicable Interest Rate Basis specified therein: (i) plus or minus the applicable Spread, if any, and/or (ii) multiplied by the applicable Spread Multiplier, if any. Commencing on the first Interest Reset Date, the rate at which interest on the Floating Rate Note shall be payable shall be reset as of each Interest Reset Date specified therein; provided, however, that the interest rate in effect for the period from the Original Issue Date to but excluding the first Interest Reset Date will be the initial interest rate (the “Initial Interest Rate”). Notwithstanding the foregoing, if a Floating Rate Note is designated in such Note as having an Addendum attached, such note shall bear interest in accordance with the terms described in such Addendum.

Interest payable on a Floating Rate Note will be determined by reference to the applicable Interest Rate Basis or Interest Rate Bases, which may, as described below, include: (i) the BA Rate, (ii) LIBOR, (iii) the Cdn. Prime Rate, or (iv) such other Interest Rate Basis or interest rate formula as may be set forth therein and described in the applicable Addendum.

The interest rate on a Floating Rate Note in effect on each day shall be the interest rate determined as of the most recent Interest Determination Date.

The interest rate on a Floating Rate Note applicable to each Interest Reset Period commencing on the Interest Reset Date with respect to such Interest Reset Period will be the rate determined as of the applicable Interest Determination Date. Each Interest Rate Basis shall be the rate determined in accordance with the applicable provisions below. The rate of interest on a Floating Rate Note will be reset daily, weekly, monthly, quarterly, semi-annually, annually or pursuant to such other period as specified in the Floating Rate Note. Unless otherwise specified in the Floating Rate Note, the Interest Reset Date(s) will be, if the Interest Reset Period set forth in the Floating Rate Note is: (i) daily, each Business Day;

Interest payable on a Floating Rate Note on any Interest Payment Date shall be the amount of interest accrued from and including the immediately preceding Interest Payment Date in respect of which interest has been paid (or from and including the Original Issue Date specified therein, if no interest has been paid), to but excluding the related Interest Payment Date; provided, however, that interest payable at maturity will include interest accrued to but excluding the Maturity Date. Accrued interest on a Floating Rate Note is calculated by multiplying the face amount thereof by an accrued interest factor. Such accrued interest factor is computed by adding the interest factor calculated for each day in the period for which accrued interest is being calculated. The interest factor for each such day shall be computed by dividing the interest rate applicable to such day by 360 if the Interest Rate Basis specified in such note is LIBOR, or by the actual number of days in the year if the Interest Rate Basis specified in such note is the BA Rate or the Cdn. Prime Rate.

A Floating Rate Note may also have either or both of the following: (i) a maximum numerical limitation, or ceiling, on the rate at which interest may accrue during any Interest Reset Period; and (ii) a minimum numerical limitation, or floor, on the rate at which interest may accrue during any Interest Reset Period. In addition to any maximum interest rate that may be applicable to a Floating Rate Note, the maximum interest rate that may be applicable to a Floating Rate Note will in no event be higher than the maximum rate permitted by the laws of Canada.

Interest on a Floating Rate Note will be payable, where the rate of interest resets, unless otherwise specified in the Floating Rate Note: (i) daily, weekly or monthly, on the third Wednesday of each month or on the third Wednesday of March, June, September and December of each year, as specified in the applicable Pricing Supplement; (ii) quarterly, on the third Wednesday of March, June, September and December of each year; (iii) semi-annually, on the third Wednesday of the months of each year specified in the Floating Rate Note; and (iv) annually, on the third Wednesday of the month specified in the Floating Rate Note and, in each case, on the Maturity Date (each, an "Interest Payment Date"). If any

The “Interest Determination Date” with respect to the BA Rate and the Cdn. Prime Rate will be the applicable Interest Reset Date, and the “Interest Determination Date” with respect to LIBOR will be the second London Business Day immediately preceding the applicable Interest Reset Date. All calculations on a Floating Rate Note shall be made by the Calculation Agent.

All percentages resulting from any calculation on a Floating Rate Note will be rounded to the nearest one-hundred-thousandth of a percentage point, with five one millionths of a percentage point rounded upwards (e.g., 9.876545% (or .09876545) would be rounded to 9.87655% (or .0987655)), and all amounts used in or resulting from such calculation will be rounded, in the case of United States or Canadian dollars, to the nearest cent or, in the case of a Specified Currency other than United States or Canadian dollars, to the nearest unit of the Specified Currency (such unit being the smallest unit of the Specified Currency in general use) (with one-half cent or one-half of the applicable unit of Specified Currency being rounded upward).

If an Interest Rate Basis for a Floating Rate Note is specified in such note as the “BA Rate”, the “BA Rate” shall be determined on the applicable Interest Determination Date (the “BA Rate Interest Determination Date”) as the rate per annum (based on a year of 365 or 366 days) equal to the arithmetic average rounded to the fifth decimal place (with .000005 being rounded up) of the bid rates of interest for Canadian dollar bankers’ acceptances, for an equivalent period to the next Interest Reset Date of the Floating Rate Note, as expressed on the Reuters CDOR page as of 10:00 a.m., Toronto time, on the BA Rate Interest Determination Date for the applicable Interest Reset Period, if three or more bid rates appear on the Reuters CDOR page at any such time. If fewer than three bid rates appear on the Reuters CDOR page at any such time, the BA Rate shall be the rate per annum (based on a year of 365 or 366 days) equal to the arithmetic average rounded to the fifth decimal place (with .000005 being rounded up) of the bid rate quotations for Canadian dollar bankers’ acceptances, for an equivalent period to the next Interest Reset Date of the Floating Rate

If an Interest Rate Basis for a Floating Rate Note is specified in such note as “LIBOR”, “LIBOR” will be determined on the applicable Interest Determination Date (a “LIBOR Interest Determination Date”), on the basis of either: (i) if “LIBOR Reuters” is specified in such note as the method for calculating LIBOR, the arithmetic average of the offered rates (unless the specified Designated LIBOR Page by its terms provides only for a single rate, in which case such single rate shall be used) for deposits in the Index Currency having the Index Maturity designated in such note, that appear on the Designated LIBOR Page specified in such note as of 11 :00 a.m., London time, on such LIBOR Interest Determination Date, if at Least two such offered rates appear (unless, as aforesaid, only a single rate is required) on such Designated LIBOR Page, or (ii) if “LIBOR Telerate” is specified in such note as the method for calculating LIBOR or if neither “LIBOR Reuters” nor “LIBOR Telerate” is so specified, the rate for deposits in the Index Currency having the Index Maturity designated in such note, that appears on the Designated LIBOR Page specified in such note as of 11 :00 a.m., London time, on such LIBOR Interest Determination Date; provided, however, that if the Index Currency is the Euro, the LIBOR Interest Determination Date must occur on a day that the TARGET System is open. If fewer than two such offered rates appear, or if no such rate appears, as applicable, LIBOR in respect of the related LIBOR Interest Determination Date will be determined in accordance with the provisions described in the immediately succeeding paragraph.

With respect to a LIBOR Interest Determination Date on which fewer than two offered rates appear, or no rate appears, as the case may be, on the applicable Designated LIBOR Page as specified in the immediately preceding paragraph, the Calculation Agent will request the principal London offices of each of four major reference banks in the London interbank market, as selected by the Calculation Agent (after consultation with the Issuer), to provide the Calculation Agent with its offered quotation for deposits in the Index Currency for the period of the Index Maturity designated in such note, to prime banks in the London interbank market at approximately 11:00 a.m., London time, on such LIBOR Interest Determination Date and in a principal amount that is representative for a single transaction in such Index Currency in such market at such time. If at least two such quotations are provided, LIBOR determined on such LIBOR Interest Determination Date will be the arithmetic average of such quotations. If fewer than two quotations are provided, LIBOR determined on such LIBOR Interest Determination Date will be the arithmetic mean of the rates quoted at approximately 11 :00 a.m., in the applicable Principal Financial Centre, on such LIBOR Interest Determination Date by three

If an Interest Rate Basis for a Floating Rate Note is specified in such note as “Cdn. Prime Rate”, the “Cdn. Prime Rate” shall be determined on the applicable Interest Determination Date (a “Cdn, Prime Rate Interest Determination Date”) as the rate (expressed as an annual percentage rate based on a year of 365 or 366 days) determined by the Issuer to be the arithmetic average (rounded to the nearest one-hundred-thousandth of one percent, with .000005 being rounded up) of the rates publicly quoted by the Schedule I Canadian chartered banks as base rates for determining interest rates on Canadian dollar prime rate loans in Canada prevailing at 10:00 a.m. (Toronto time) on the Cdn. Prime Rate Interest Determination Date.

At the request of the Holder of a Floating Rate Note, the Calculation Agent shall provide to such Holder the interest rate thereon then in effect and, if determined, the interest rate which shall become effective as of the next Interest Reset Date .

The Issuer may issue Amortizing Notes and shall set forth in such notes a table specifying repayment information with respect to such notes and any additional terms and conditions thereof.

The Issuer may issue Extendible Notes and shall set forth in such notes the specific terms of the extension of such notes, including without limitation the date or dates on which the Issuer’s option to extend can be exercised and whether the option can be exercised with respect to some but not all of the outstanding principal balance of such notes, and any additional terms and conditions thereof, including without limitation the specific terms and conditions upon which the maturity of such notes may be extended.

The Notes issued in the United States shall be issued as Certificated Notes in accordance with the provisions of Section 3.4.

If, at any time, a holder of a Certificated Note bearing the U.S. Securities Act Legend wishes to transfer its interest to a Person required or permitted to take delivery thereof in the form of an interest in a Global Note, the Trustee will cancel the definitive certificate representing such Certificated Note, the Issuer shall execute and deliver to the Trustee for authorization and registration by it a replacement Global Note in a principal amount equal to the sum of (x) the principal amount of the relevant Global Note then deposited with CDS and (y) the principal amount of the cancelled Certificated Note. The Trustee shall exchange and deliver to CDS the replacement Global Note against surrender and delivery of the Global Note deposited with CDS immediately prior to the exchange and CDS will be instructed by the Trustee to make appropriate entries in the book entry accounts established and maintained by CDS or its nominee for financial institutions acting as direct and indirect participants of CDS on behalf of Beneficial Owners to include the transferee of the Certificated Note.

If, at any time, a person holding an interest in a Global Note wishes to transfer a Note to a person in the United States who is required to comply with resale restrictions imposed under the U.S. Securities Act, the Issuer shall execute and deliver to the Trustee for authorization and registration a Certificated Note representing such Note bearing the U.S. Securities Act Legend and a replacement Global Note in a principal amount equal to the difference between (x) the principal amount of the relevant Global Note then deposited with CDS and (y) the principal amount of the Certificated Note to be issued to the person in the United States. The Trustee shall exchange and deliver to CDS the replacement Global Note against surrender and delivery of the relevant Global Note deposited with CDS immediately prior to the exchange and CDS will be instructed by the Trustee to make appropriate entries in the book entry accounts established and maintained by CDS or its nominee for financial institutions acting as direct and indirect participants of CDS on behalf of beneficial owners to record the transfer of the Note to the person in the United States.

to pay the Costs of lssuance of the Notes;

to make payments of principal, interest and premiums, if any, on previously issued Notes or Bonds;

to fund the growth and expansion of its electrical transmission network in Alberta through capital development projects and acquisitions;

to repay bank indebtedness, if any, under the Issuer’s credit facilities;

to repay outstanding commercial paper, if any;

to fund certain Funds (including any Sinking Funds) and Reserve Funds maintained by the Issuer pursuant to the Master Indenture and this Sixteenth Supplemental Indenture;

to fund other capital projects related to the operation and maintenance of the Business; and

for general business purposes.

Notes issued in exchange for a Global Note or to persons in the United States pursuant to Subsections 2.8(a) and 2.8(c) shall be issued as Certificated Notes in authorized denominations, shall have the same benefits and be subject to the same terms and conditions as that Global Note (except insofar as such terms and conditions specifically relate to that Global Note), shall be registered in the names and denominations as the Issuer shall direct and shall be delivered as directed by the persons in whose names such Certificated Notes are to be registered. The Certificated Notes shall be in substantially the form, mutatis mutandis, of the Global Note, except as provided in Section 3.4(b) and without the Global Note legend set out thereon. Unless otherwise determined by the Issuer, it shall not be necessary for any Certificated Notes to be lithographed or printed with steel engraved borders.

Each Certificated Note originally issued to a person in the United States, as well as all certificates issued in exchange for or in substitution of the foregoing securities, will bear the U.S. Securities Act Legend; provided that, if any such securities are being sold outside the United States in accordance with Rule 904 of Regulation S and provided that the Issuer is a Foreign Issuer at the time of sale, the legend may be removed by providing a declaration to the Trustee, as registrar and transfer agent, to the effect set forth in Schedule “C” hereto (or in such other form as the Trustee may from time to time prescribe) and, provided further, that, if any Notes are being sold, or on the request of the holder at such time as the Notes may be sold without restriction, pursuant to Rule 144 under the U.S. Securities Act, such legend may be removed, provided that the Trustee has received a written opinion of U.S. counsel of recognized standing reasonably satisfactory to the Issuer to effect that, or such certification or other information that the Trustee may reasonably require to determine that, such legend is no longer required under applicable requirements of the U.S. Securities Act or state securities laws in the United States of America.

Except as provided in Subsection 3.4(b), if a Certificated Note tendered for transfer bears the U.S. Securities Act Legend and the transferee is a person in the United States, the Certificated Note issued to such transferee shall also bear the U.S. Securities Act Legend.

The Trustee shall maintain a list of all registered holders of Certificated Notes bearing the U.S. Securities Act Legend.