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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Which is not a type of lightning stroke?
Cloud-to-Ground (CG)
Intra-Cloud (IC)
Ground-to-Ground (GG)
Ground-to-Cloud
Ground-to-Ground (GG)
Quick Summary: Lightning strokes are primarily categorized based on the direction of leader propagation (downward or upward) and the polarity of the charge (positive or negative). Common types include direct strokes (striking structures or earth), induced strokes (via electromagnetic fields), and cloud-to-cloud discharges.
Lightning strokes are primarily categorized based on the direction of leader propagation (downward or upward) and the polarity of the charge (positive or negative). Common types include direct strokes (striking structures or earth), induced strokes (via electromagnetic fields), and cloud-to-cloud discharges.
E=dV — Electric field intensity between cloud and ground
Ipeak=ZsurgeVcloud — Peak discharge current
A lightning stroke initiates when the potential gradient between the cloud and earth (or another cloud) exceeds the dielectric strength of air (approx3textMV/m). A stepped leader descends, creating an ionized path, followed by a return stroke that carries the high-current discharge. This process involves rapid ionization of a channel, resulting in massive current surges often measured in kiloamperes.
Negative cloud-to-ground strokes account for approximately 90% of lightning strikes.
Positive lightning is rarer but typically carries significantly higher peak currents and charge transfer.
Upward streamers are initiated from tall grounded structures like skyscrapers or transmission towers.
Lightning Protection Systems (LPS) use rods to intercept these strokes safely to the ground.
Grounding systems effectively divert surge energy.
Surge arresters limit overvoltage to safe equipment levels.
Unpredictable nature of stroke polarity and intensity.
Potential for back-flashover in transmission lines.
Protection of power system substations.
Shielding of high-voltage transmission lines.
Option C is marked as 'None of the above' or an undefined category in the provided context, making it the odd one out among valid physical lightning stroke definitions.
Direct strokes are the most destructive as they dump the full charge directly into the power system conductor.
C is correct — It represents an invalid category in the standard classification of lightning phenomena.
Always relate lightning protection to the Basic Insulation Level (BIL) of equipment; insulation must withstand the transient voltages produced by these strokes.