(1) Voltage means the voltage existing with loads operating under stable conditions. Each electric utility must adopt standard voltages for its different classes of standard voltage service and file these standards with the commission in the form of tariffs.

(2) Electric utilities must maintain the voltage on their distribution system reasonably constant and any allowed variation must be a gradual change in voltage as a result of normal changes in load.

The voltage on each primary distribution feeder must be maintained as follows:

(a) Voltage variations may not be more than five percent above or below the standard voltage adopted; and

(b) The total voltage variation from minimum to maximum value may not exceed eight percent of the standard voltage.

A utility may allow greater voltage variation than that specified in this rule in case of emergency service or when service is supplied directly from a transmission line. A utility may also permit greater voltage variations in an area where the revenues received do not justify close voltage regulation. In such cases, electric utilities must provide the best voltage regulation that is economically and technically practicable under the circumstances.

(3) Voltage variations in excess of those specified, caused by the action of the elements, by infrequent and unavoidable fluctuations of short duration due to system operation, or by the operation of power apparatus on the customer's premises which necessarily requires large starting currents and only affects the user of such apparatus, will not be considered a violation of this rule.

(4) Customers must control and operate the equipment on their premises in such a way that its starting and operating characteristics will not cause an instantaneous voltage drop of more than four percent of the standard voltage as measured at the point of interconnection with the electric utility. Likewise, customers must control and operate their equipment in such a way that it does not cause damage or interfere with the normal operation of the electric utility's facilities or of the facilities or equipment of another customer, such as causing excessive flicker in other customers' lights. Utilities are not required to monitor customers' equipment and its interactions with third party or utility equipment on an ongoing basis.