Lightning arrestor

Lightning Arrestor

A lightning arrestor (or lightning arrester) is a device used in electrical power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The primary purpose of a lightning arrestor is to divert the high voltage surges from lightning to the earth, preventing them from travelling along the power lines and damaging transformers, electrical equipment, and causing power outages.

Types of Lightning Arrestors

There are several types of lightning arrestors, each designed for specific applications and operating conditions. The most common types include:

• Rod Gap Arrestors: Simple devices that consist of two rods with a gap in between. When the voltage exceeds a certain level, the air between the rods becomes ionized, allowing the surge to jump across the gap and be diverted to the ground.
• Valve Type Arrestors: These use a series of semiconductor elements that change resistance based on the voltage level. Under normal conditions, they have high resistance, but when a surge occurs, their resistance drops, allowing the surge to be diverted to the ground.
• Metal Oxide Varistors (MOVs): These are the most widely used type of lightning arrestor in modern electrical power systems. MOVs consist of zinc oxide (ZnO) pellets that change resistance with the applied voltage. They can handle very high surge currents and have a fast response time.

Installation and Operation

Lightning arrestors are typically installed in close proximity to the equipment they are protecting. For power transmission and distribution systems, they are mounted on poles or towers along the transmission lines and connected between the conductor and the ground. In telecommunications systems, they are installed where cables enter a building to protect the internal network.

When a lightning surge travels down a power line, the lightning arrestor detects the surge and diverts it to the ground, thereby protecting the electrical equipment downstream. The arrestor must be capable of quickly returning to its high resistance state to be ready for any subsequent surges.

Maintenance

Regular maintenance of lightning arrestors is crucial for ensuring their reliability and longevity. This includes visual inspections, checking for any physical damage, and measuring the electrical properties to ensure they are within the specified range. Damaged or deteriorated arrestors must be replaced to maintain the protection level of the electrical system.

Safety Considerations

While lightning arrestors significantly reduce the risk of damage from lightning surges, they cannot guarantee absolute protection. It is also essential to have a well-designed grounding system to ensure that the diverted surges are effectively dissipated into the earth.

Conclusion

Lightning arrestors are a critical component of electrical and telecommunications systems, providing protection against the potentially devastating effects of lightning strikes. By diverting surges to the ground, they prevent damage to equipment, minimize downtime, and enhance the overall reliability of the power supply.