Concept of Surge Voltage: 

Every electrical device has a specific dielectric strength against surge voltages. If the level of a surge voltage exceeds this strength, malfunctions or damage can occur. Surge voltages with very high amplitudes in the kilovolt range are generally transient Over voltages, which means they have a comparatively short duration, ranging from a few Microseconds to several hundred microseconds. The high amplitude and short duration, in turn, Mean very abrupt voltage increases and high voltage differences, the effects of which can be Protected against only with surge protection.

Types of Surge: 

Mep-SPS-Surge Concept

1.Lightning Surge: (10/350 microsec waveform)

Sources:  Strike on Power Supply, Telephone Lines, Internet Lines or sudden lightning

discharge

2.Internal Surges: (8/20 microsec waveform)

Sources:  Internal switching of Resistive and Inductive Loads

Surge Protection Devices (SPD) : Dehn Make

• Surge Arrester (Type-I SPD)