Study of Different Lightning Arresters and Identification of Parts
Lightning arresters (also called surge arresters or lightning protection devices) are safety devices used to protect electrical systems from lightning strikes and other high-voltage surges. They divert the surge to the ground, preventing damage to electrical equipment. There are several types of lightning arresters, and each type serves the same purpose but with different operating principles, construction, and areas of application.
Types of Lightning Arresters
- Rod-type Lightning Arrester
- Disc-type Lightning Arrester
- Gap-type Lightning Arrester
- Non-Gapped (Metal Oxide) Lightning Arrester
- Combined Lightning Arrester and Surge Protector
1. Rod-type Lightning Arrester
A rod-type lightning arrester is one of the simplest designs, often used in low-voltage systems. It consists of a metal rod that acts as the collector for the lightning strike.
Parts of Rod-type Lightning Arrester:
- Metal Rod (Conductor): A tall rod made from copper or aluminum that is designed to intercept the lightning strike.
- Base or Mounting: The base supports the metal rod, often attached to a structure or grounded pole.
- Grounding System: The metal rod is connected to the ground through a conductor to safely dissipate the lightning strike's energy into the Earth.
- Insulator: An insulator is used to isolate the metal rod from the surrounding structure and to prevent accidental electrical conduction.
Working Principle:
- When a lightning strike occurs, the rod provides a path for the lightning to travel from the air to the ground. The current is safely dissipated into the ground.
2. Disc-type Lightning Arrester
A disc-type lightning arrester is often used in medium to high-voltage power transmission systems. It is typically made up of several porcelain or ceramic discs stacked together. This type provides a higher insulation level and can handle more energy compared to a rod-type arrester.
Parts of Disc-type Lightning Arrester:
- Porcelain Discs: These are the primary insulating material used to protect the electrical components and ensure that the arrester withstands high voltages. Each disc provides insulation, and multiple discs are stacked together to form the arrester.
- Metallic Conductors: These connect the individual discs, allowing for electrical current to pass when needed (in case of a surge).
- Metal Oxide Varistor (MOV): MOVs are used to limit the voltage that can pass through the arrester, protecting the system from excessive voltage.
- Terminal Connectors: These are the points where the arrester is connected to the electrical system for conducting lightning surge energy to the ground.
Working Principle:
- The arrester is connected to the power system and serves to divert high-voltage surges away from the system. In the event of a lightning strike, the surge travels through the arrester, and the MOV absorbs the excess energy before safely discharging it to the ground.
3. Gap-type Lightning Arrester
A gap-type lightning arrester is a type of traditional arrester that uses an air gap to break the electrical connection under normal conditions. In the event of a voltage surge, the gap closes, and the current flows through the arrester, discharging to the ground.
Parts of Gap-type Lightning Arrester:
- Air Gap (Spark Gap): The air gap is the key component. It remains open under normal conditions and only closes when a surge is detected, allowing the lightning current to pass.
- Electrode (Metal Plates): Metal plates are located on either side of the gap. When the air gap closes, these electrodes conduct the current.
- Insulation: Insulating materials like porcelain or ceramic are used to prevent unwanted discharge and ensure that the arrester only conducts during a surge.
- Grounding: A conductor is used to connect the arrester to the ground, allowing the electrical charge to dissipate safely.
Working Principle:
- When the system experiences a high-voltage surge, the air gap closes, and the electrodes allow current to pass through the arrester to the ground. After the surge is over, the gap opens again to prevent further current flow.
4. Non-Gapped (Metal Oxide) Lightning Arrester
A non-gapped or metal oxide lightning arrester (MOV arrester) is one of the most modern types of lightning arresters. These are used in power systems to protect against both lightning strikes and surges. They are more reliable and compact than traditional gap-type arresters and provide continuous protection.
Parts of Metal Oxide Lightning Arrester:
- Metal Oxide Varistor (MOV): The MOV is the key component that absorbs high voltages and prevents them from passing through. It consists of metal oxide material that behaves like an insulator under normal conditions but becomes conductive when exposed to high voltage.
- Ceramic Housing: A ceramic or porcelain housing encases the MOV to protect it from environmental conditions and mechanical damage.
- Terminal Connectors: These are the terminals where the arrester is connected to the power system for conducting the surge current to the ground.
- Grounding System: A conductor connects the arrester to the ground, allowing the energy to be safely dissipated into the Earth.
Working Principle:
- Under normal conditions, the MOV does not conduct, but when a surge or lightning strike occurs, the MOV becomes conductive and diverts the surge current to the ground. Once the surge is over, the MOV returns to its non-conductive state.
5. Combined Lightning Arrester and Surge Protector
A combined lightning arrester and surge protector is a hybrid device that serves both as a lightning arrester and a surge protector. It is commonly used in industrial, commercial, and residential applications to protect electrical systems from both direct lightning strikes and smaller surges from other sources.
Parts of Combined Lightning Arrester and Surge Protector:
- Lightning Arrester Section: The traditional components of a lightning arrester, such as the rod, gap, or MOV, are used to handle lightning strikes and high-voltage surges.
- Surge Protection Device (SPD): This component includes technologies like varistors or gas discharge tubes, which protect against smaller electrical surges.
- Grounding System: Like other arresters, the combined arrester connects to a grounding system for safe dissipation of electrical energy.
Working Principle:
- The arrester works by absorbing and redirecting lightning strikes and high-voltage surges to the ground, while the surge protection component deals with smaller voltage spikes that occur due to switching or other disturbances in the electrical network.
Summary of Parts Common to All Lightning Arresters
| Component | Description |
|---|---|
| Insulator | Material that isolates the arrester from the structure and prevents accidental discharges. |
| Grounding System | Provides a safe path for the lightning current to be discharged into the Earth. |
| Electrodes/Conductors | Conduct the current from the lightning strike to the ground. |
| Protection/Surge Component | Metal oxide varistor (MOV) or spark gap that absorbs and dissipates excess voltage. |
| Housing/Enclosure | Protects internal components from the environment (usually made of porcelain or ceramic). |
Conclusion
Lightning arresters are vital components of any electrical system, as they provide protection from lightning strikes and high-voltage surges. There are different types of arresters, such as rod-type, disc-type, gap-type, and metal oxide arresters, each designed for specific applications. The parts of a lightning arrester typically include components for conducting current, insulating materials for safety, and grounding systems to dissipate energy into the Earth. The modern metal oxide varistor (MOV) arrester offers continuous protection and is widely used in power systems today.
