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Lightning Arresters: Your Ultimate Guide to Types and Functions

In a little town surrounded by hills, people are worried about storms and lightning. An old person shared stories about a special protector called a lightning arrester. When the town started using these protectors, their homes became safer during thunderstorms. People were happy and surprised at how these simple devices kept them safe.

 It’s important to know that sometimes if there’s a direct lightning strike or a really strong surge of electricity, these protectors might not work perfectly and could cause damage to connected things. This guide is here to help understand more about these protectors, how they work, the different types, and why they’re important for keeping everyone safe from lightning.

What is a Lightning Arrester?

A lightning arrester, also known as a lightning rod or surge arrester, is a vital component designed to protect structures and electrical systems from the damaging effects of lightning strikes. Its primary function is to divert the excessive electrical energy from a lightning strike safely to the ground, preventing potential harm to people and property.

Purpose of a Lightning Arrester

The main purpose of a lightning arrester, also sometimes called a lightning arrestor or lightning isolator, is to protect electrical power systems and telecommunication systems from the damaging effects of lightning strikes.

Here’s a breakdown of how they work:

  • Standing Guard: Lightning arresters are installed at key points within a system, acting like mini lightning rods.
  • High Voltage Haven: They have a high-voltage terminal that connects to the power line or communication cable.
  • Grounded for Safety: Another terminal connects to a grounding system, which is essentially a safe path for electricity to travel directly to the earth.
  • Voltage Spike Slayer: When a powerful surge of electricity from a lightning strike hits the power line, the arrester diverts that current away from the delicate electrical equipment and safely down to the ground through the grounding system.

During a normal flow of electricity, the arrester doesn’t interfere. But when a sudden surge like a lightning strike happens, the arrester acts like a safety valve, releasing the excess pressure (voltage) and protecting the equipment.

Lightning arresters come in various forms depending on the application:

  • Power Lines: These are typically larger and more robust to handle the high voltages on power grids.
  • Telecommunication Lines: These are designed for the lower voltages used in phone and internet lines.

By safeguarding electrical and communication systems from lightning damage, arresters help to:

  • Prevent power outages and disruptions
  • Protect valuable equipment from costly repairs or replacements
  • Ensure reliable operation of critical infrastructure

Types of Lightning Arresters

Lightning arresters come in various forms, each suited for specific voltage levels and applications within electrical power systems and telecommunication lines. Here’s a breakdown of some common types:

Protecting Different Voltages:

  • Rod Gap Arrester: A simple design often used for low-voltage applications like telephone lines. It consists of a metal rod with a gap separating it from a grounded metal plate. During a high voltage surge, the gap is bridged, diverting the current to the ground.
  • Sphere Gap Arrester: Similar to the rod gap arrester, but it uses metal spheres instead of rods to create a more uniform gap for voltage breakdown. These are also used for low-voltage applications.
  • Horn Gap Arrester: Employs V-shaped metal horns with a gap in between. This design provides a more gradual path for high-voltage surges to travel, making it suitable for medium-voltage applications.
  • Multi-Gap Arrester: An improvement on the horn gap arrester, it uses multiple sets of horns with progressively smaller gaps. This allows for a more precise response to different voltage surges, offering better protection for medium-voltage systems.

Advanced Technologies:

  • Expulsion Type Lightning Arrester: This type utilizes a fuse element within a sealed housing. During a surge, the fuse element melts, creating a path for the current to flow to the ground.
  • Valve Type Lightning Arresters: These employ a valve-like mechanism that opens during a high voltage surge, diverting the current to the ground. They are known for their fast response time and are used for protecting higher voltage systems.
  • Thyrite Lightning Arrester: This type relies on a special material called Thyrite, which has non-linear electrical resistance properties. Thyrite conducts electricity at high voltages, diverting surge currents to the ground, while offering high resistance during normal operating voltages.
  • Metal Oxide Varistor (MOV) Lightning Arrester: The most widely used type today, MOV arresters utilize metal oxide varistors (MOVs) – electronic components with a non-linear resistance characteristic. Similar to Thyrite arresters, MOVs conduct high voltage surges while offering high resistance during normal operation.

Additional Considerations:

  • Spark Gap Arresters: These are a less common type that utilize a spark gap to divert surges. However, they can generate radio interference and are not widely used in modern systems.

By understanding the different types of lightning arresters and their characteristics, we gain a deeper appreciation for the crucial role they play in safeguarding electrical and communication infrastructure from the damaging effects of lightning strikes.

Lightning Arrester vs. Surge Arrester

Lightning Arrester:  As the name suggests, lightning arresters are specifically designed to safeguard against the powerful surges caused by lightning strikes. These strikes induce extremely high voltage spikes that can overwhelm and damage electrical equipment.

Surge Arrester:  Surge arresters take a broader approach, protecting against a variety of transient voltage spikes. These spikes can originate from various sources, including:

  • Switching transients: When electrical loads (like motors) are switched on or off, it can cause temporary voltage spikes.
  • Power faults: Short circuits or other faults within the power system can create sudden voltage surges.
  • Electrostatic discharge (ESD): Buildup of static electricity can discharge rapidly, causing voltage spikes.
Feature Lightning Arrester Surge Arrester
Primary Threat Direct lightning strikes Various transient voltage spikes
Location Installed outdoors Installed indoors (panels) or at equipment
Function Diverts high voltage to ground Diverts voltage spikes to ground
Design Larger and more robust Smaller and more versatile

Combination of Lightning and Surge Arresters for Protection

In some cases, lightning arresters and surge arresters can be used together to provide a layered defense for electrical systems.  Lightning arresters act as the first line of defense against powerful lightning strikes, while surge arresters provide additional protection from internal voltage spikes and transients.

Here’s an analogy to remember the difference:

Imagine your house is an electrical system. A lightning arrester is like a lightning rod on your roof, diverting a direct strike away from your home.  A surge arrester, on the other hand, is like a surge protector plugged into your wall outlets, safeguarding your electronic devices from smaller voltage fluctuations within your house’s wiring.


Lightning arresters play a crucial role in shielding against the powerful impact of lightning strikes. Their diverse range, tailored for specific applications, highlights the importance of comprehending their intricacies to establish a robust strategy for securing critical infrastructure and maintaining the consistent functionality of electrical and communication networks.

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