Voltage regulation on any electrical system is defined as the difference in voltage between periods of no load and periods of full load on the system. Characteristics of the system and the amount of load will determine the extent of the voltage regulation. To provide good electric service to customers served from the distribution system, it is necessary to maintain voltage variations within a very limited range. The voltage variation to residences has been standardized from a high limit of 126 volts to a low limit of 114 volts for a nominal 120-volt secondary service voltage. The term nominal voltage designates the line-to-line voltage, as distinguished from the line-to-neutral voltage. It applies to all parts of the system or circuit.

Electrical equipment is designed to operate on a certain voltage, and best operation is obtained when that rated voltage is applied. The effect of low voltage on heating-type appliances such as heaters, toasters, irons, and ranges is an increase in heating time. Low-voltage conditions cause motors to operate at decreased efficiency. They draw more current from the line, have less starting and running torque, and may overheat to the extent that they might experience thermal failure. Incandescent lights operate less efficiently, give less light, and in the case of fluorescent lights may not operate at all.

High-voltage conditions are also detrimental to the operation of electrical equipment. Heating-type elements, light bulbs, and electron tubes have a shorter life span because of high voltage. Motors and other magnetic equipment...