What causes electrical transients?

The simple act of turning on (or off) a light, motor, copy machine or any other electrical device can disturb the electrical circuit and create transients. In general, the larger the load current the greater the disturbance when the load is switched off or on. The switching of high ampacity loads such as electric welders and electric motors are known to create transients. Studies have shown that a majority of transients (roughly 80%) are generated inside a given facility. Cloud-to-cloud lightning discharges or nearby lightning strikes are capable of creating electric field intensities in the hundreds to thousands of volts per meter. A two meter length of wire (i.e. a power or signal conductor) exposed to an electric field intensity of 300 volts per meter can develop an induced transient voltage of 600 volts (2 meters X 300 volts/meter = 600 volts). If this 600 volt transient appears across an unprotected power, telephone, data, or coaxial line the result can be system destruction. A driver knocking down a utility power pole or even events considered minor, such as a curious squirrel exploring a utility power transformer can be responsible for creating power interruptions and significant transient disturbances. Tree branches and even wet kite strings touching power lines have disrupted energy flow and caused power line transients. Noisy electrical neighbors sharing your electrical distribution system, such as welding shops or manufacturing facilities can also be a major source of transients.