The two types of noise are Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI). Noise usually occurs when an electrical device or electrical apparatus is placed too close to a motor or transformer. This type of disturbance can often be noticed as "static" on a radio or on a monitor screen.

Transients are high voltage bursts of energy which are of short duration. These power surges are caused by switching procedures within the utility. Sudden isolated power outages in another part of the network, lightning strikes and whenever large loads are shut down abruptly.

Low voltage disturbances are drops in voltage resulting in dimmed lights and slowed-down electric motors. They generally occur when the demand for power exceeds the systems capacity, as in a heavily loaded or overloaded circuit. More localized causes are large electric motors starting up or other concentrated and immediate demands for power.

No-voltage disturbances are the easiest to detect because they are the result of total loss of power. Causes can range from storm-related damage to power lines to failed transformers or tripped circuit-breakers. A power outage can be very short (eight to ten milliseconds) or in weather related situations, may last several hours.

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