A surge arrester is a crucial protective device used in electrical power systems to safeguard equipment from damaging overvoltage transients, such as those caused by lightning strikes or switching operations. By providing a controlled path for excess voltage to travel safely to the ground, surge arresters play a vital role in preventing costly damage and system outages.
In both medium-voltage and high-voltage networks, surge arresters ensure the reliability and safety of power delivery. Their use extends across substations, transmission lines, renewable energy systems, and industrial applications. As modern power infrastructure evolves with the integration of smart grids and renewable energy, the importance of advanced surge protection solutions has grown significantly.
Working Principle of Surge Arresters
How Surge Arresters Protect Equipment from Voltage Spikes
A surge arrester is designed to act as the first line of defense against transient overvoltages in electrical systems. Under normal operating voltages, the surge arrester behaves like an open circuit—it remains in a non-conductive state, allowing regular power flow to proceed without interruption. This is essential to ensure that the arrester does not interfere with normal operations.
However, when an unexpected voltage spike occurs—such as during a lightning strike, line fault, or switching operation—the arrester instantly changes its behavior. It becomes conductive and offers a low-resistance path for the excessive voltage to be safely discharged to the ground. By doing this, the surge arrester prevents the high-voltage surge from reaching sensitive equipment like transformers, switchgear, inverters, or communication systems. Once the overvoltage event passes and the line voltage returns to normal, the arrester rapidly reverts to its original high-resistance, non-conductive state. This ability to switch between non-conductive and conductive modes in microseconds is what makes surge arresters highly reliable for overvoltage protection.
Role of Non-Linear Resistance (MOV Blocks)
The key to a surge arrester’s functionality lies in its internal components—most notably the Metal Oxide Varistor (MOV) blocks. These MOV blocks, typically composed of zinc oxide (ZnO), exhibit non-linear resistance properties. In simple terms, they allow very little current to pass at normal operating voltages but dramatically reduce their resistance when exposed to overvoltage conditions. This makes them ideal for absorbing surge energy while minimizing disruption to the system.
When a high-voltage transient appears, the MOV elements respond instantly, allowing a large surge current to flow through the arrester to the ground. This fast-acting response—often in less than a microsecond—ensures that the overvoltage is clamped before it can propagate downstream and damage equipment. The zinc oxide core, used in most modern Metal Oxide Arresters (MOA), enhances performance, eliminates the need for external spark gaps, and improves overall reliability.
Discharge and Recovery Mechanisms
After the surge energy has been successfully discharged, the surge arrester must recover its original state to remain functional for future events. Thanks to the unique material characteristics of ZnO-based MOVs, the arrester automatically returns to a high-resistance condition. This rapid recovery prevents any continuous current from flowing through the arrester, which would otherwise lead to thermal degradation or failure.
Moreover, modern surge arresters with gapless construction offer self-healing properties. They can endure multiple surge events over their lifetime without significant performance deterioration. This not only reduces the need for frequent maintenance but also enhances system reliability, making surge arresters indispensable in both low and high-voltage power infrastructure.
Main Types of Surge Arresters
Zinc Oxide Arrester with Gap
The Zinc oxide arrester with gap represents an earlier generation of arresters. In these devices, zinc oxide blocks are combined with spark gaps. The spark gap acts as a trigger, initiating conduction only when the voltage exceeds a certain threshold. While effective, this design has limitations in response speed and reliability. The presence of the gap can lead to delayed action and higher energy discharge requirements.
Gapless Zinc Oxide Arrester
The modern standard in surge protection is the Gapless zinc oxide arrester. This type uses only ZnO blocks without any spark gaps. Gapless arresters offer several benefits:
This design has become the default in both medium and high-voltage systems due to its simplicity, durability, and superior performance.
MOA (Metal Oxide Arrester)
The term MOA is commonly used to refer to surge arresters that use metal oxide varistors, particularly zinc oxide. MOAs are available in various voltage classes and are designed for different use cases—from distribution networks to ultra-high voltage transmission lines.
MOAs are widely used across global power grids, and their performance has been proven through decades of use in all types of climates and operating conditions.
Station-Class vs. Distribution-Class Arresters
Station-class arresters are designed for high-voltage applications such as substations and transmission lines. They offer high energy absorption capacity and are often used in conjunction with critical infrastructure like transformers and circuit breakers.
On the other hand, distribution-class arresters are used in medium-voltage applications, such as on poles and in pad-mounted transformers. These are more compact and economical but are still highly effective at protecting against transient voltages.
Applications
Power Substations
Substations are critical nodes in the power grid, and surge arresters are essential in preventing damage to expensive equipment such as transformers, breakers, and busbars. MOAs are typically installed at the terminals of transformers and switchgear.
Medium and High-Voltage Transmission Lines
Both 34kV Surge Arrester and 132kV Surge Arrester models are used along transmission lines to protect insulators and conductors from lightning strikes and switching surges. Arresters are placed at regular intervals and at points where lines transition between overhead and underground.
34kV Surge Arrester: Ideal for medium-voltage distribution networks, wind farms, and industrial facilities.
132kV Surge Arrester: Suitable for high-voltage transmission lines and large substations, providing robust protection against external and internal overvoltage events
Industrial and Utility-Scale Equipment
Factories, water treatment plants, and renewable energy installations (like solar farms and wind parks) rely on surge arresters to protect their sensitive and expensive equipment. The presence of reliable surge protection reduces downtime and extends equipment life.
In renewable energy systems, surge arresters are used at inverter terminals, transformer inputs, and even at the solar panel array level to prevent lightning-induced damage.
Advantages and Limitations
High Response Speed
One of the most significant advantages of modern surge arresters, especially gapless MOAs, is their ultra-fast response time. They can react to voltage surges within microseconds, preventing even brief overvoltage exposure that could otherwise damage sensitive components.
Longevity and Maintenance Considerations
Surge arresters are generally low-maintenance. However, their effectiveness can diminish over time due to repeated surges or environmental stress (e.g., pollution, moisture, UV exposure). Routine inspections, surge counters, and thermal imaging can help detect early signs of degradation.
Key factors that affect arrester life include:
Frequency and magnitude of surges
Environmental conditions (e.g., salt fog, industrial pollution)
Quality of installation (e.g., grounding resistance)
Limitations
No surge arrester can offer 100% protection if it's improperly rated or installed. It’s also important to note that surge arresters degrade slightly with every surge event. Therefore, periodic testing and preventive replacement are necessary in high-risk zones.
Summary
Surge arresters play a vital role in ensuring the safety and longevity of modern power systems. As electrical networks evolve to include renewables, energy storage, and smart technologies, reliable surge protection becomes more critical than ever. From traditional zinc oxide arresters with gaps to advanced gapless MOA-based designs, the technology has advanced significantly. Today’s 34kV and 132kV surge arresters offer exceptional performance, fast response, and minimal maintenance. For tailored solutions in distribution and transmission applications, Hebei Jiuding Electric Co., Ltd. stands out as a trusted manufacturer. To explore high-quality surge arrester products or get expert guidance, contact Hebei Jiuding ElectricCo., Ltd. today.
