Instantaneous overvoltages (impulse voltages) are those that appear within a few microseconds (micro 1/100,000) and a few milliseconds (milli 1/1000) with a magnitude varying between 5 to 10KV. Voltages with such magnitude equal 8-10 times the tolerance limits of electronic devices.
Instantaneous overvoltages can be network-induced or atmospheric-induced. Atmospheric-induced voltages are known as “lightning impacts”. Transient voltage fluctuations, voltage dips, short interruptions, slow and quick voltage changes and harmonics are examples of network-induced impacts. There are also electrical switching incidents that have an effective role on the formation of instantaneous overvoltages.