Introduction
Direct effect and indirect effect of lightning strike can cause damage to the living beings. Structures and the electrical or electronics devices. The main and most effective measure for protection of structures against physical damage is considered to be the lightning protection system (LPS). IEC 62305 explains about the Internal and External lightning protection system. Internal Lightning Protection System will protect the electrical and electronic equipment inside the structure from the lightning impulse surge
What is Surge?
Surges are very high magnitude and low duration disturbances on the power frequency that causes damage to the electrical & electronic equipment.
Lightning Protection Zones:
IEC 62305-4 has differentiated the lightning protection zones based on the strike.
- LPZ OA - The zone which is protected from Direct strike by providing external lightning
protection.
- LPZ OB - The zone which is protected from magnetic field of direct lightning strike
- LPZ 1 - The zone which is protected from the damage caused by indirect strike. By
limiting the surge current due to lightning.
- LPZ 2....n - The zone which is protected from the damage caused by surges at the boundary.
Surge Protection Device:
Surge Protection Devices (or SPDs) are units combining several protection components. They are designed to be incorporated in an installation to protect all electric, electronic, and data-processing equipment from transient over voltages. They divert the transient surges to the ground thereby protecting the equipment.
Types of Surge Protection Device:
Type 1 Surge Protectors:
This type of surge protection device need to withstand the surge current of the direct lightning strike. As per EN 61643-11 and IEC 61643-11 standards Class 1 test need to be done by injecting current 10/350 μs impulse current in order to simulate the direct lightning strike consequence.
Type 2 Surge Protectors:
To with stand the transient surges the SPD should be tested Class 2 test as per EN 61643-11 and IEC 61643-11 standards. 8/20 µs impulse current to be inject.
Type 3 Surge Protectors:
To protect the specific equipment from the surges Class 3 test should be done as per EN 61643-11 and IEC 61643-11 standards. Combination of 1.2/50 µs & 8/20 µs current to be inject in order to perform Class 3 test.
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