Publish Time: 2025-11-07 Origin: Site
Electrical systems form the foundation of everyday life, and it is crucial to protect them from damage or failure. Surge arresters and lightning arresters are common components used to protect these systems. Though they are similar, there are key differences in how they are used. This article will describe their differences to help you know which one to use.
A surge arrester, also called a surge protector, is a device used to protect electrical systems from damage caused by surges or transient voltage. These surges can come from blackouts, lightning, or switching operations in the power distribution network.
The working principle of a surge arrester is simple. When there is a sudden voltage spike, the surge arrester passes extra voltage to the earthing instead of allowing it to get to the equipment. Once the voltage returns to normal, the arrester resumes its high-resistance state, ensuring uninterrupted system performance. Thus, it protects sensitive equipment from damage.
There are different types of surge arresters, each used in different settings. Station class arresters are used in high-voltage substations. Intermediate class arresters are used in medium-voltage networks. Distribution class arresters are used to protect equipment in overhead distribution lines and transformers. Secondary class arresters are used in low-voltage systems.
A lightning arrester, also called a lightning rod or a lightning conductor, is a device that protects equipment from lightning. It is usually made of copper or aluminum and must be wired to the ground by a wire or rod.
When lightning strikes, it uses a low-resistance path to safely discharge the strike to the ground. Doing so intercepts the strike so that it doesn't penetrate and cause extreme disorder or damage in electrical systems.
Once the discharge is complete, the arrester returns to its normal insulating state.
The lightning arrester is mounted on the top of transmission poles or substation towers. It is also installed at entry points in overhead lines. Additionally, it is placed at telecommunication towers and building rooftops for adequate protection.
The basic function of a surge arrester is to protect electrical and electronic equipment from transient overvoltages. These overvoltages are often caused by internal system events such as switching operations, insulation failures, or lightning strikes. It acts as a protective device that limits voltage to a safe level by diverting extra voltage to the ground. Thus, it prevents insulation breakdown and extends the service life of the equipment.
On the other hand, a lightning arrester acts as a shield against direct lightning strikes. When lightning hits the power lines, the arrester provides a low-resistance path that discharges extremely high current to the earth. Thus, it prevents high current from reaching sensitive equipment.
A surge arrester is designed to protect the insulation of electrical components by keeping voltage levels below their insulation withstand capacity. It guarantees that equipment insulation is not exposed to voltages beyond its rated limit. For example, in a 33kV distribution system, a surge arrester may be rated to arrest surges below 90kV, maintaining integrity across systems.
On the other hand, a lightning arrester is designed for a much higher insulation coordination because its function is to handle surges from direct lightning strikes. Voltages in this scenario can reach several hundred kilovolts. Its insulation design can withstand flashover or puncture caused by lightning impulses.
A surge arrester operates across a broad range of system voltages, from low-voltage systems in residential networks to high-voltage systems in transmission and distribution networks. It is designed to discharge overvoltages caused by capacitor switching, cable energization, or motor starting. These surges can last for microseconds to milliseconds and may not reach a high range, but may still cause damage if left unchecked.
In contrast, a lightning arrester protects systems from external voltage surges that come from lightning strikes. The voltage level can reach several million volts, creating an immediate need for discharge through a low-resistance path. It is installed in medium to high-voltage distribution systems to handle much higher voltage levels than those of a surge arrester.
The nominal discharge current is considered the capacity of the arrester to discharge a large current to the ground without failure. For surge arresters, the nominal discharge current usually ranges from 5 kA to 20kA. Such a rating means the highest current the device may repeatedly discharge without any failures. They are typically tested in order to guarantee that they can manage smaller surges during their lifespan of service, besides providing continuous protection.
In contrast, a lightning arrester has a discharge current of nominal discharge current between 30 kA to 200kA. It is subjected to a simulation of actual lightning discharge. It is constructed using strong internal elements that can withstand such huge energy bursts. It is not used for frequent surges, but must perform excellently when a strike occurs.
A surge arrester is usually placed close to the equipment it protects, such as transformer terminals or switchgear points. This layout reduces the length of distance between the arrester and the equipment and will achieve quicker response time. It is typically mounted in an indoor or enclosed substation or within a distribution board to shield electronic equipment against damage.
Conversely, a lightning arrester is placed on the outside, and it is typically placed on the top or highest exposed points of an electrical system. It is usually present on top of transmission towers and roofs of buildings. This configuration enables it to intercept lightning before it destroys any electrical equipment.
A surge arrester operates based on nonlinear characteristics, using metal oxide varistors (or MOVs) or silicon carbide (SiC) elements. Under normal voltage conditions, the arrester possesses excellent resistance, acting as an open circuit. When a high voltage occurs, its resistance drops sharply, allowing the excess current to pass through the ground. Once the voltage returns to a normal level, it returns to its excellent resistance state and resumes normal operation.
In contrast, a lightning arrester uses a spark-over discharge. That is, when lightning strikes, the air gap inside the arrester begins to ionize and conduct electricity. This allows excess current to flow to the earth. After the discharge, the arrester returns to its insulation mode between the line and the ground.
As mentioned earlier, a surge arrester is made of metal oxide varistor (MOV) blocks and grading rings. These blocks are enclosed in a porcelain or polymer housing. The MOV blocks are placed between two electrodes, forming a voltage-dependent resistor assembly. This design ensures a fast response time when there is an overvoltage. The polymer housing provides moisture resistance, while the grading rings provide uniform distribution.
In comparison, a lightning arrester has a more rugged construction. It has spark gaps, series resistors, and earth electrodes. The spark gap fires when the lightning voltage exceeds its value. The series resistor helps control currents after discharge. The electrode ensures that the lightning current is safely conducted to the ground.
A surge arrester only provides localized protection within electrical systems. It is installed inside the premises and therefore prevents damage to transformers, switchgears, and other delicate equipment that would otherwise be damaged in the network. It keeps the voltage at the desired levels to eliminate degradation or breakdown of equipment. This guarantees reliability and a constant supply of power.
A lightning arrester, however, offers broad protection. It is used to counter external hazards, which occur due to direct lightning strikes, and directs such discharges before they can reach equipment. Unlike surge arresters, it does not control internal voltage surges within equipment. Its coverage area is that of providing overall protection to the equipment and the operators.
The flow capacity indicates how much surge current an arrester can safely conduct to ground or earth. For a surge arrester, its energy-handling capability is usually between 5 kA and 20 kA. This range varies depending on the voltage class and application. But the flow capacity allows it to manage frequent surges while maintaining stability and reliability.
For a lightning arrester, its flow capacity or energy-handling capability lies between 30kA and 200kA or higher. It provides a direct, low-resistance path for lightning current to reach the earth, preventing it from traveling into the equipment. Its superior flow capacity makes it useful in outdoor electrical systems and high-exposure areas.
The final difference between a surge arrester and a lightning arrester is their application. A surge arrester is applied in industrial plants, substations, and commercial buildings, where surges are usually low, such as those caused by internal switching operations. Additionally, it protects transformers and circuit breakers from overvoltages. It is also used in telecommunication and renewable energy systems to protect inverters from surges.
On the other hand, a lightning arrester is installed outdoors in areas exposed to direct lightning. Examples of these areas include transmission towers, tall buildings, substations, power plants, and telecommunication masts. It prevents strikes from penetrating the electrical network, providing insulation and protection from damage.
Key Differences In: | Surge Arrester | Lightning Arrester |
Function | Protects electrical equipment from transient overvoltages caused by switching operations, faults, or induced lightning surges. | Protects systems and structures from direct lightning strikes by diverting lightning energy safely to the ground. |
Insulation Level | Designed to maintain equipment insulation below its withstand voltage. | Built with high insulation strength to handle direct lightning impulses and prevent flashover. |
Voltage Level & Source | Handles internal voltage surges within systems, ranging from 230V to 400kV networks. | Manages external high-voltage discharges, often reaching millions of volts. |
Nominal Discharge Current | Rated typically between 5 kA to 20 kA | Rated between 30 kA to 200 kA |
Installation | Installed close to equipment like transformers or switchgear. | Mounted at exposed points such as tower tops or rooftops. |
Working Principle | Operates using nonlinear resistance. | Works on spark-over discharge. |
Construction & Components | Comprises MOV blocks, electrodes, and insulated housings (porcelain or polymer). | Contains spark gaps, resistors, and earth electrodes within a rugged outdoor housing. |
Protection Scope | Offers localized protection for equipment within electrical systems. | Provides broad external protection against direct strikes. |
Flow Capacity | Handles moderate energy surges repeatedly without damage. | Withstands very high-energy lightning currents in single discharge events. |
Application | Used in industrial, commercial, residential, and renewable energy systems for transient protection. | Applied in transmission lines, substations, towers, and tall structures for lightning protection. |
Selection criteria should be based on the following:
System voltage level: Choose an arrester whose rated voltage matches the voltage of the system you are protecting.
Location of installation: Consider where the arrester will be used. Surge arresters are best for indoor installation, while lightning arresters are best for areas exposed to lightning.
Expected surge intensity: Understanding the expected surge intensity in a region will also help you know which arrester to choose. If the region is prone to lightning, then use lightning arresters. For frequent surges due to switching operations, surge arresters are most suitable.
Equipment sensitivity: Different equipment has various tolerance levels to overvoltages. Check your equipment to ensure it can enhance operational safety.
Surge arresters and lightning arresters are both used to protect equipment, but their key differences tell them apart. This blog has extensively covered that topic, so you can make informed decisions.
If you are looking for ways to improve electrical safety, Haivol Electrical is where you need to be. We have quality surge arresters and lightning arresters that meet different levels of protection. Contact us now for more information.
No, a lightning arrester is not the same as a surge arrester. While a lightning arrester protects equipment from overvoltage caused by direct lightning strike, a surge arrester protects equipment from surges caused by lightning strikes and internal events like blackouts.
A surge arrester can protect against lightning-induced surges but not against a direct lightning strike.
Yes, a lightning arrester prevents damage to equipment by discharging excess current to the ground when lightning strikes.
No, surge protective devices do not work without an earth or grounding system. They need it to safely discharge current to the ground so as not to damage sensitive equipment.
You should replace your arrester at least annually. You should also perform periodic checks to ensure they are in good condition.
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