Secondary Voltages. The voltage at the utility's service terminals, as installed for each customer, shall be maintained within the Limits specified in the table below. If a utility adopts any standard voltage not included in the table, it shall advise the Commission in order that the Commission may establish appropriate voltage limits. When 3-phase service is provided, the utility shall exercise reasonable care to assure that the phase voltages are balanced. Primary Voltages. The following limits shall apply where the utility supplies service at primary voltage: Industrial Customers. For service rendered principally for industrial or power purposes, the voltage may not exceed 7-1/2 percent above or 7-1/2 percent below the standard nominal voltages as filed in the utility's rules. Sales For Resale. For service rendered to public utilities and others for resale, the nominal voltage shall be as mutually agreed upon by the parties concerned. The allowable voltage may not exceed 7-1/2 percent above or 7-1/2 percent below the agreed upon nominal voltage without the express approval of the Commission. Special Contract Exceptions. The limitations in §§B(1) and B(2), of this regulation, do not apply to special contracts in which the customer specifically agrees to accept service with unregulated voltage. Exceptions to Voltage Requirements. It will not be considered a violation when voltages outside of the prescribed limits are caused by any of the following: Action of the elements; Service interruptions; Temporary separation of parts of the system from the main system; Infrequent fluctuations not exceeding 5 minutes' duration; or Other causes beyond the control of the utility.