The electrical and electronic equipments inside the structure can be protected from the very high magnitude lightning impulse surges which exists for a very short duration by using suitable Surge Protection Devices.
Surge Protection Devices (or SPDs) are units combining several protection components like Metal Oxide Varistor, spark gaps, gas discharge tubes, thermal protection fuse and indicators to protect the electrical and electronic devices from voltage surges. They divert the transient surges to the ground thereby protecting the equipments. Hence, SPD in combination with good earthing system shall be used to protect the electrical and electronic equipment from the damages dues to these surges.
The problems due to surges were present from the earlier days but it was not taken into consideration because of the lesser sensitivity of the loads which were used earlier. The higher sensitivity of the sophisticated electronic devices towards these transient surges due to lightning and switching impulses emphasis the need for surge protection devices.
The damages due to surges of lower magnitude may not be immediate but it reduces the overall lifetime of the product. Hence these surges are considered as the silent killers of electronic equipment. The effects on the electrical devices due to surges are mainly classified into three types as,