Research also reveals that many power quality issues are due to improper or poor ground connections at the meter, or within the customer's building itself. Momentary occurrences of high voltage are known as voltage swells and could occur as a result of a sudden decrease in electrical load. A loose neutral connection, or faulty wiring on a 120-volt circuit can allow a voltage swell to damage electronic equipment. Equipment operating at 240-volts such as air conditioners, water heaters, ranges, ovens, etc, are not typically affected by voltage swells. Momentary occurrences of low voltage are known as voltage sags and can occur as a result of an overloaded electrical system, either on the utility side, or on the internal wiring of the customer's building.
Electrical faults can cause sags on adjacent circuits or feeders.
No voltage is a complete loss of power that can last from milliseconds to several hours. Momentary interruptions usually last less than one minute. Symptoms of these problems for sensitive electronic equipment include audible or visual distortion, erratic data problems or system error messages. Impulses Impulses, known as transient surges, or voltage spikes, are the most common cause of damage to electronic devices and other sensitive equipment. These impulses can be hundreds of volts above normal, but last only millionths of a second.