Lightning Arrester – Definition, Working, Diagram, Types & Location of Lightning Arrester

A lightning arrester is a device that provides a low-impedance path to ground for lightning or transient overvoltages, effectively protecting the electrical system from high-voltage surges. It operates by limiting the voltage across its terminals to a safe value and shunting the excess energy to the ground.

What is a Lightning Arrester?

A lightning arrester, also known as a surge diverter, is an electrical device used to protect power systems and equipment from the damaging effects of lightning strikes and voltage surges. It is designed to divert high-voltage spikes safely to the ground, preventing damage to electrical equipment and systems.

Working Principle of Lightning Arrester

1. Spark Gap: A set of electrodes separated by a small gap. When a surge occurs, the voltage across the gap increases, ionizing the air and creating a conductive path to discharge the surge to the ground.
2. Non-linear Resistor (Varistor): Made of materials like silicon carbide or zinc oxide, this resistor exhibits a non-linear V-I characteristic. At normal operating voltages, it presents a high resistance. During surges, its resistance decreases, allowing the excess current to flow to the ground.

Step-by-Step Working of Lightning Arrester

1. Under normal conditions, the arrester remains inactive, isolating the electrical system from the ground.
2. When a surge or lightning strike occurs, the voltage across the arrester rises.
3. The spark gap conducts, and the non-linear resistor limits the voltage to a safe level.
4. The excess energy is diverted to the ground, protecting the system.
5. Once the surge subsides, the arrester returns to its non-conductive state.

V-I Characteristics of Non-linear Resistor:

The V-I characteristic (see Figure 1(b)) of a non-linear resistor used in lightning arresters shows that the voltage across the device increases non-linearly with the current. At low current levels, the voltage is relatively low. However, as the current increases due to a surge, the voltage rises sharply, allowing the device to conduct and divert the surge.

Types of Lightning Arresters

1. Rod Gap Arrester: A simple design with two electrodes separated by an air gap. It is primarily used for protection in low-voltage systems.
2. Horn Gap Arrester: Similar to the rod gap, but with horn-shaped electrodes to improve the arc extinguishing capability.
3. Expulsion Type Arrester: Uses a series gap and a vented chamber to expel the ionized gases during a surge.
4. Valve Type Arrester: Combines a spark gap with a series of non-linear resistors for high-voltage applications.
5. Metal Oxide Varistor (MOV) Arrester: The most common type, using zinc oxide for efficient surge suppression without a series gap.
6. Station Class Arrester: Designed for high-voltage substations to protect large equipment.
7. Distribution Class Arrester: Used in distribution networks to protect transformers and lines.
8. Intermediate Class Arrester: Positioned between station and distribution class arresters for medium-voltage systems.

Location of Lightning Arresters

Lightning arresters are strategically placed in power systems to ensure maximum protection. Common locations include:

1. Substations: Installed at the incoming and outgoing lines to protect transformers and other critical equipment.
2. Transmission and Distribution Lines: Positioned along power lines to protect against lightning-induced overvoltages.
3. Electrical Panels: Used in residential and commercial installations to safeguard appliances and devices.
4. Communication Systems: Deployed to protect antennas, satellite dishes, and telecommunication equipment.
5. Industrial Equipment: Installed to shield machinery and control systems from voltage spikes.

Applications of Lightning Arresters

1. Power Systems: Protection of transformers, circuit breakers, and other high-voltage equipment.
2. Telecommunication Networks: Shielding against voltage surges caused by lightning.
3. Railway Systems: Protecting signaling equipment and power supply systems.
4. Solar Power Systems: Preventing damage to inverters and other solar components.
5. Wind Turbines: Safeguarding against lightning-induced surges.

Advantages of Lightning Arresters

1. Enhanced Protection: Safeguards sensitive equipment from voltage surges.
2. Cost-Effective: Reduces maintenance and replacement costs of electrical systems.
3. Reliability: Operates efficiently under diverse environmental conditions.
4. Compact Design: Easy to install in various applications.
5. Improved System Stability: Prevents interruptions caused by voltage surges.

Disadvantages of Lightning Arresters

1. Limited Lifespan: Requires periodic replacement or maintenance.
2. Voltage Limitation: May not protect against extreme overvoltages beyond its rating.
3. Installation Complexity: Requires precise placement for effective protection.
4. Cost: Initial installation can be expensive for large systems.
5. Dependency on Grounding: Requires a proper grounding system for effective operation.

Difference Between Lightning Arrester and Surge Arrester

Aspect	Lightning Arrester	Surge Arrester
Purpose	Protects against lightning-induced high-voltage surges.	Protects against voltage surges caused by switching operations or other transient events.
Application	Installed at substations, transmission lines, and distribution systems.	Installed near sensitive equipment, such as motors, transformers, or electronics.
Design	Typically includes a spark gap and a non-linear resistor.	Often uses a metal oxide varistor (MOV) or similar surge suppression components.
Operation	Activated by high-energy surges caused by lightning strikes.	Operates during voltage transients from switching or faults.
Voltage Rating	Designed to handle extremely high voltages.	Designed for lower voltage levels compared to lightning arresters.
Primary Use	Diverts lightning strikes to the ground to protect the power system.	Limits overvoltage spikes to prevent damage to electrical devices.
Typical Locations	Substations, high-voltage transmission lines, and outdoor installations.	Near electronic equipment, transformers, and residential panels.
Frequency of Operation	Rare, activated only during lightning events.	Frequent, activated during switching transients and minor surges.

Conclusion

Lightning arresters play a vital role in protecting electrical systems and equipment from the destructive effects of lightning and voltage surges. By providing a safe path for excess voltage to reach the ground, they ensure the stability and longevity of power systems. Despite some limitations, their advantages make them an indispensable component in modern electrical installations.