Zinc Oxide Surge Arrester: Structure, Function, and Manufacturing Process
A zinc oxide surge arrester (ZnO surge arrester) is a critical protective device used in high-voltage and medium-voltage power systems to safeguard equipment from transient overvoltages such as lightning strikes and switching surges. Known for its excellent nonlinear characteristics, high energy absorption, and reliability, the ZnO surge arrester is widely used in substations, overhead lines, transformers, and power distribution grids.
What Is a Zinc Oxide Surge Arrester?
A surge arrester using ZnO varistors to absorb and limit overvoltage, protecting power equipment.
A zinc oxide surge arrester is a protective device that prevents damage from lightning overvoltage and internal switching surges. It uses metal oxide varistors (MOVs) as the core component, allowing it to respond instantly to voltage spikes. Compared with SiC (silicon carbide) arresters, ZnO technology provides:
Higher energy handling capability
Better voltage–current nonlinear behavior
No series spark gaps required (gapless design)
Faster response
Longer service life
Nooa Energy supplies ZnO surge arresters for distribution networks, substation protection, and transmission line insulation coordination.
Core Components of a ZnO Surge Arrester
MOV blocks + housing + sealing + accessories = complete arrester assembly.
A typical zinc oxide surge arrester consists of:
ZnO varistor blocks (metal oxide discs)
FRP/epoxy fiberglass rods for mechanical strength
Silicone rubber housing (sheds) for insulation and hydrophobicity
Aluminum alloy or stainless steel end fittings
Sealing components to keep moisture out
Grounding terminal and mounting accessories
The silicone rubber housing plays a major role in outdoor pollution resistance, making the arrester ideal for coastal, desert, and industrial environments.
Working Principle of Zinc Oxide Surge Arresters
Nonlinear MOV characteristics allow the arrester to conduct only during overvoltage and block current otherwise.
Under normal system voltage, ZnO blocks act as insulators, allowing only a tiny leakage current.
During an overvoltage event:
The ZnO blocks become conductive
The arrester clamps the voltage to a safe level
Excess energy is discharged safely to ground
Once the surge ends, the arrester returns to its insulating state
This fast, precise response protects transformers, substations, distribution lines, switchgear, and power equipment.
Production Steps of Zinc Oxide Surge Arresters
MOV production → core assembly → silicone housing → curing → sealing → testing.
Below is a detailed breakdown of Nooa Energy’s surge arrester production process:
1. Raw Material Preparation and Zinc Oxide Powder Mixing
ZnO powder + additives mixed to create varistor formulation.
High-purity zinc oxide powder, bismuth oxide, manganese oxide, and other additives are accurately weighed.
Mixed thoroughly using ball mills or blending machines to achieve uniform particle distribution.
2. Pressing and Forming the ZnO Varistor Blocks
Powder compressed into discs with precise size and density.
Powder is pressed into discs using high-pressure hydraulic presses.
The discs (MOV blocks) are shaped with precise dimensions suitable for different voltage classes.
3. Sintering the Varistor Blocks
High-temperature heat treatment forms crystalline boundaries and nonlinear characteristics.
MOV discs are sintered in a kiln at 1100–1300°C.
Grain boundaries develop to create the nonlinear voltage-current behavior essential for surge protection.
After sintering, the blocks are inspected for cracks, porosity, and resistivity.
4. Housing Preparation (Silicone Rubber Molding)
High-voltage silicone sheds are molded with excellent hydrophobicity and tracking resistance.
Liquid silicone rubber is molded into shed profiles using injection or compression molding.
The housing provides insulation, UV resistance, and anti-pollution performance.
5. Core Assembly
MOV blocks stacked with electrodes, then wrapped and compressed for mechanical integrity.
ZnO varistor discs are stacked with aluminum electrodes.
Fiber-reinforced epoxy (FRP) rods and insulating spacers are added.
The stack is compressed and mechanically fastened.
The internal structure is secured to withstand bending, torsion, and mechanical stress.
6. Sealing and Silicone Housing Injection
Silicone housing is applied over the core to ensure complete moisture-proof protection.
The MOV stack is inserted into the silicone housing.
End fittings are attached and sealed with moisture-proof materials.
High-quality sealing ensures long-term outdoor reliability.
7. Electrical and Mechanical Quality Testing
Each arrester undergoes full IEC routine testing for safety and performance.
Typical tests include:
Power frequency reference voltage test
Leakage current measurement
Lightning impulse withstand test
Partial discharge test
Pressure test on joints
Mechanical bending and tension tests
Aging and thermal stability tests
Types of Zinc Oxide Surge Arresters
Classified by voltage level, installation location, and purpose.
Common types include:
Distribution surge arresters (10kV–33kV)
Substation-class arresters (66kV–220kV)
Transmission line surge arresters
Gapless polymer-housed arresters
Station-type surge arresters with metal fittings
Advantages of ZnO Surge Arresters
High nonlinear behavior, long life, strong weather resistance.
Key benefits:
Fast response time
High energy absorption capability
Excellent hydrophobicity due to silicone housing
Maintenance-free operation
High resistance to pollution and UV
Suitable for harsh outdoor environments
Lower residual voltage compared to SiC arresters
FAQ: Zinc Oxide Surge Arresters
1. What standards do ZnO surge arresters follow?
Most follow IEC 60099-4 for metal-oxide surge arresters without gaps.
2. Does Nooa Energy provide surge arresters for different voltage levels?
Yes. Nooa Energy manufactures surge arresters for 10kV to 220kV systems, customizable upon request.
3. What is the typical lifespan of a ZnO surge arrester?
Under normal conditions, 15–30 years, depending on pollution, UV exposure, and system stress.
4. How are arresters tested before shipment?
Each unit undergoes routine electrical tests, sealing inspection, and mechanical testing.
5. Can surge arresters be customized for coastal or polluted areas?
Yes. Enhanced silicone sheds and stronger sealing systems are available.
6. Do you have KEMA certificate？
Yes. Pls contact us now for checking.
