N.C. Gen. Stat. § 122D-12
Subject to the rights of the holders of the bonds of the Authority, the Authority may issue from time to time its bonds for the purpose of refunding any bonds of the Authority then outstanding, together with the payment of any redemption premiums thereon and interest accrued or to accrue to the date of redemption of such outstanding bonds. All such refunding bonds of the Authority shall be issued, sold or exchanged, and delivered, shall be secured, and shall be subject to the provisions of this Chapter in the same manner and to the same extent as any other bonds issued by the Authority pursuant to this Chapter, unless otherwise determined by resolution of the Authority. Refunding bonds issued by the Authority as herein provided may be sold or exchanged for outstanding bonds of the Authority and, if sold, the proceeds thereof may be applied, in addition to any other authorized purposes, to the purchase, redemption or payment of such outstanding bonds.
Pending the application of the proceeds of any such refunding obligations, with any other available funds, to the payment of the principal, accrued interest and any redemption premium on the obligations being refunded, and, if so provided or permitted in the resolution authorizing the issuance of such refunding obligations or in the trust agreement securing the same, to the payment of any interest on such refunding obligations and any expenses in connection with such refunding, such proceeds may be invested in direct obligations of, or obligations the principal of and the interest on which are unconditionally guaranteed by, the United States of America which shall mature or which shall be subject to redemption by the holders thereof, at the option of such holders, not later than the respective dates when the proceeds, together with the interest accruing thereon, will be required for the purposes intended.
N.C. Gen. Stat. § 122D-12