■ An impulsive transient is a brief, unidirectional variation in voltage,
current, or both on a power line. The most common causes of impulsive
transients are lightning strikes, switching of inductive loads, or switching
in the power distribution system. These transients can result in
equipment shutdown or damage if the disturbance level is high enough.
The effects of transients can be mitigated by the use of transient voltage
suppressors such as Zener diodes and MOVs (metal-oxide varistors).