How do lightning rods prevent lightning strikes from reaching people

Source: This post on How do lightning rods prevent lightning strikes from reaching people has been created based on the article “How do lightning rods prevent lightning strikes from reaching people?” published in The Hindu on 11th November 2024.

Why in news?

Rising lightning strikes due to climate change kill around 24,000 globally each year, including 2,887 in India in 2022. Petitions in India urge lightning to be declared a natural disaster to aid survivors, highlighting the importance of lightning rods for protection.

About Lightning Rods

1.  Lightning Rod: A lightning rod is a metal conductor placed on high structures to attract lightning strikes. The rod is designed with a pointed shape that intensifies the electric field around it, creating a preferred path for lightning. This strong electric field ionizes the air near the rod, facilitating a safe pathway for the current to flow.

2. Why Lightning Strikes a Rod First: Electricity seeks the most direct and easiest path to the ground.  The rod is placed at an elevated point, becoming the first “hand” lightning “reaches” for. Installing it on top of buildings ensures that lightning encounters the rod first, diverting it from other nearby structures or people.

Current Dissipation Mechanism

1. How the Current is Directed into the Ground: Electric current flows from areas of high to low electric potential. The earth, with its vast potential to absorb charges, acts as a nearly “infinite” receptacle for electricity. A grounding wire connects the lightning rod to the earth, allowing the charge to dissipate safely into the ground.

2. How it works: When lightning hits a rod, it induces a large current in electrical systems. Engineers use lightning arresters: components that redirect high currents away from sensitive equipment to protect grid-connected systems and appliances.

Potential Lightning Rod Failures

1. Conditions for Failure: Incorrect installation: If the rod is placed at an improper height or angle, is poorly grounded, or installed too close to another structure.

2. Structural issues: Corrosion, improper design, or damage due to lack of maintenance can compromise effectiveness.

3. Natural factors: Severe weather, multiple thunderstorms, or ground charges can affect the rod’s ability to attract lightning.

4. Improvements in Lightning Rod Design: Engineers optimize rods to make them as attractive as possible to lightning within a certain range. Ensuring minimum distances between the rod and ground improves its effectiveness.

Safety Measures and Risks of Lightning Rods

1. Design Safety for Current Flow: The components of a lightning rod system are designed to safely transport the lightning strike’s charge into the ground. Wire bends should avoid U-shapes to prevent arcing and short circuits. High-conductivity areas of soil or concrete encased electrodes, developed by Herbert Ufer, are often used to improve grounding.

2. International Safety Standards:  The International Electrotechnical Commission (IEC) provides standards to guide safe lightning rod design and installation. Standards address potential failure points and establish best practices for installation, helping to minimize risks and protect nearby people and property.

UPSC Syllabus: Science and technology