What Is a Lightning Arrester?
A lightning arrester, also known as a surge diverter or surge arrester, is a protective device used to safeguard electrical systems from the damaging effects of lightning strikes and voltage surges. It functions by providing a low-resistance path for excess voltage to be diverted safely to the ground, thereby protecting sensitive equipment from high-voltage transients.
How Does A Lightning Arrester Work?
1. Basic Operation: When a lightning strike or a surge occurs, the lightning arrester activates and creates a conductive path to the ground. This allows the surge current to bypass electrical equipment, preventing potential damage. Once the surge has passed, the arrester returns to its non-conductive state, ready for the next event.
2. Construction: Lightning arresters typically consist of one or more gaps or electrodes that are designed to break down at a specific voltage level. When the voltage exceeds this threshold, the gap ionizes and allows current to flow through it to the ground. Common materials used in modern arresters include metal oxide varistors (MOVs) and silicon carbide.
What Are the Different Classifications of Lightning Arresters?
1. By Application
Station Arresters: These provide the highest level of protection with lower discharge voltages and higher energy absorption capabilities. They are typically used in large substations and areas with high surge activity, operating at voltages ranging from 3 kV to 684 kV.
Intermediate Arresters: Designed for smaller substations and applications such as underground cable protection and dry-type transformers. They have moderate protective characteristics and are rated between 3 kV to 120 kV.
Distribution Arresters: These offer the lowest level of protection and are used primarily in medium voltage networks (typically less than 52 kV). They are suitable for protecting distribution transformers and associated equipment.
2. By Voltage Rating
Low-Voltage Surge Arresters: Rated under 1000 V, these devices provide surge protection for consumer applications and low-voltage distribution systems.
Medium-Voltage Surge Arresters: Typically rated between 3 kV and 30 kV, these arresters are used in power distribution systems to protect transformers and cables.
High-Voltage Surge Arresters: Also known as station-class arresters, these are used for voltages above 30 kV and provide robust protection for substation equipment.
3. By Construction Type
Metal Oxide Varistor (MOV) Arresters: Commonly used in modern surge protection devices, these arresters utilize metal oxide materials to absorb surges effectively.
Gapped Arresters: These include types like rod gap, sphere gap, and horn gap arresters, where an air gap is designed to ionize under high voltage conditions, diverting the surge to ground.
Valve Type Arresters: These utilize a valve mechanism to control the flow of current during a surge event, ensuring that excess voltage is safely redirected.
