Unless approved by a three-fifth majority vote of the electorsvoting thereon at a regular or special election, the City shall not sell, exchange, lease, or in any way dispose of any property, easement, equipment, privilege, or asset belonging to and appertaining to any municipally owned utility. All contracts, negotiations, licenses, grants, leases, or other forms of transfer in violation of this Section shall be void and of no effect as against the City. The restrictions of this Section shall not apply to the sale or exchange of any particles of machinery or equipment of any city-owned utility which are worn out, or useless, or which have been, or which, with advantage to the service, could be replaced by new and improved machinery or equipment.