AdvancedTopic 102 of 106Electrical Engineering
Lightning and surge protection
Arresters and shielding divert transient overvoltages safely.
In depth
Lightning currents reach 30 kA+ with rise times of microseconds. Protection: air terminals, down conductors, earthing and surge protective devices (SPDs) at service entrance, distribution and equipment (Type 1, 2, 3). Zones concept limits transient overvoltages.
Key points
- Rolling-sphere method
- Let-through voltage
- Bonding to equalise potentials
ExampleAn SPD clamps a 6 kV surge to under 1.5 kV.
What is Lightning and surge protection?
Arresters and shielding divert transient overvoltages safely.
Why is it important to understand lightning and surge protection?
Transient overvoltages from lightning or switching can destroy equipment, so arresters and shielding protect electronics and power systems.
What does a surge arrester do?
It conducts high transient currents to earth when the voltage exceeds a threshold, then returns to high impedance after the surge passes.
Why is surge protection important for electronics?
Electronics often fail from a single surge, and an arrester reduces the peak voltage that reaches the equipment.
How is Lightning and surge protection used in practice?
Typical applications include installing surge protectors at the service entrance of a house, shielding an overhead line from direct lightning strikes and selecting a surge arrester for a substation transformer.
What should I learn before Lightning and surge protection?
Study "Earthing systems" first (topic 101 of 106 in Electrical Engineering). It covers the groundwork this topic builds on.
What are the key points of Lightning and surge protection?
Rolling-sphere method. Let-through voltage. Bonding to equalise potentials.
Can you give an example of Lightning and surge protection?
An SPD clamps a 6 kV surge to under 1.5 kV.
What comes after Lightning and surge protection?
The next topic is "Electrical measurements and sensors", which builds directly on this one.
How difficult is Lightning and surge protection?
It is classed as Advanced in Electrical Engineering (topic 102 of 106). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Electrical Engineering.