(a) For so long as any bonds are outstanding and unpaid, the rates, fees, and charges for electric power and energy charged and collected by a municipality shall be so fixed as to provide revenues sufficient to pay all costs of and charges and expenses in connection with the proper operation and maintenance of its electric system, and all necessary repairs, replacements, or renewals thereof, to pay when due the principal of, premium, if any, and interest on all bonds, including bonds subsequently issued for additions, improvements, and betterments to its electric system, payable from such revenues, to create and maintain reserves as may be required by any ordinance or trust indenture authorizing or securing bonds, and to pay any and all amounts which the municipality may be obligated to pay from electric system revenues by law or contract.
(b) For so long as any contract for the purchase of electric power and energy is in effect, the rates, fees, and charges for electric power and energy charged and collected by a municipality may be fixed to provide sufficient revenues to secure payments of amounts due under the contract and to comply with the terms of the contract. Any contract shall be approved by ordinance of the governing body of the purchasing municipality, and the ordinance shall be published one (1) time in a newspaper of general circulation in the municipality. Any contest of the ordinance shall be barred at the end of thirty (30) days after the ordinance is published.
(c) Any pledge made by a municipality pursuant to this chapter shall be valid and binding from the date the pledge is made. The revenues so pledged and then held or thereafter received by the municipality or any fiduciary on its behalf shall immediately be subject to the lien of the pledge without any physical delivery thereof or further act, and the lien of the pledge shall be valid and binding as against all parties having claims of any kind in tort, contract, or otherwise against the municipality without regard to whether the parties have notice thereof.
(d) The ordinance, trust indenture, or other instrument by which a pledge is created need not be filed or recorded in any manner.