The Commission, each commissioner and each person employed by the Commission shall have the right at any and all times to inspect the property, plant and facilities of any electrical utility and to inspect or audit at reasonable times the accounts, books, papers and documents of any electrical utility. For the purposes herein mentioned the Commission, each commissioner and each person employed by the Commission may during all reasonable hours enter upon any premises occupied by or under the control of any electrical utility. The Commission, each commissioner and any employee of the Commission authorized to administer oaths shall have power to examine under oath any officer, agent or employee of such electrical utility in relation to the business and affairs of such electrical utility, but written record of the testimony or statement so given under oath shall be made and filed with the Commission. Any person other than a commissioner demanding the right to perform any act authorized by this section shall produce written authority from the Commission authenticated by its seal.