Medium-voltage surge arrester 3EJ series

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Product overview
Medium-voltage surge arresters from Siemens Energy provide overvoltage protection for distribution networks and critical electrical equipment up to 72.5 kV. Designed for industrial and utility applications, these arresters limit transient overvoltages from lightning and switching events to protect transformers, switchgear and rotating machines.

Overview of medium-voltage surge arresters
Siemens Energy offers multiple designs and series to meet different application requirements. Selection is based on the protected equipment, required energy absorption and site conditions. Key variants include polymer-housed designs with reinforced cages or wraps and porcelain-housed types for very high short-circuit duty.

Key features

• Wide voltage range: Suitable for applications up to 72.5 kV.
• High energy absorption: Types available for medium to very high energy requirements.
• Advanced housing materials: Silicone rubber (polymer) and porcelain options for environmental and fire performance.
• Reliable pressure relief: Engineered venting prevents ejection of internal parts during overloads.
• Maintenance-free surface: Hydrophobic silicone surfaces reduce moisture-related degradation.
• Standards compliance: Designed and tested to IEC 60099-4.

Siemens Energy medium-voltage surge arrester portfolio
The portfolio includes distribution-class polymer designs, high-energy series and porcelain-housed arresters. Configurations are available to match installation types, mechanical requirements and insulation coordination needs.

3EK distribution class surge arresters

• 3EK7 (Cage Design™): FRP cage for mechanical strength with silicone rubber molded directly on metal-oxide (MO) elements to prevent moisture ingress and partial discharges.
• 3EK8 (Wrap design): Silicone molded on MO elements with fiberglass wrap allowing controlled arc escape and excellent moisture resistance.

3EJ family — high energy absorption
3EJ arresters are designed for high energy duties and low protection levels to protect generators, motors, arc furnaces, dry-type transformers, airfield lighting, cable sheaths and converters for drives.

• 3EJ2: Rated voltages up to 54 kV, medium energy absorption.
• 3EJ3: Up to 54 kV, high energy absorption.
• 3EJ4: Up to 54 kV, very high energy absorption; available in indoor version.
• 3EJ0: Optimized for up to 15 kV with very low protection level for cable networks.
• 3EJ9: For up to 15 kV with very low residual voltage, recommended for power plants and extensive cable systems.

Plug-in surge arresters (3EH4)
3EH4 plug-in arresters protect transformers and switchgear from switching and lightning overvoltages. Features include plug-and-socket connections to EN 50180 / EN 50181, suitability up to 52.5 kV, rugged construction and low residual voltages for good insulation coordination.

Porcelain-housed arresters for special applications (3EP-G)
3EP-G porcelain arresters provide very high short-circuit current capability (up to 300 kA) for generator and motor protection. They feature robust porcelain housing, directional pressure relief and high-sealing integrity to prevent moisture ingress.

Technical highlights and benefits
Silicone rubber and porcelain housings, high-temperature vulcanized silicone for hydrophobicity and fire safety, reinforced mechanical designs and engineered pressure-relief systems improve reliability and safety in MV distribution environments.

Technical comparison

• Voltage range: Up to 72.5 kV
• Housing materials: Silicone rubber (3EK, 3EJ), porcelain (3EP-G)
• Mechanical reinforcement: FRP cages or fiberglass wraps
• Pressure relief: Engineered directional venting
• Hydrophobicity: High-temperature vulcanized silicone rubber
• Fire performance: Silicone rubber is fire-retardant and self-extinguishing
• Short-circuit capability: Up to 300 kA (3EP-G)

Applications

• Distribution networks: Protection for transformers, switchgear and lines.
• Industrial facilities: Protection for motors, generators and process equipment.
• Renewable energy: Surge protection for wind, solar and inverter systems.
• Utilities and power plants: Equipment protection to improve grid reliability.

Why choose Siemens Energy medium-voltage surge arresters?
Wide product range across voltage and energy classes, polymer and porcelain housings, engineered pressure-relief solutions and compliance with IEC 60099-4 for reliable overvoltage protection.

Technical specifications

• Voltage range: up to 72.5 kV
• Housing materials: silicone rubber (polymer) and porcelain
• Series/types: 3EK (3EK7, 3EK8), 3EJ (3EJ2, 3EJ3, 3EJ4, 3EJ0, 3EJ9), 3EH4 (plug-in), 3EP-G (porcelain)
• Mechanical reinforcement: FRP cages or fiberglass wraps
• Hydrophobicity: HTV silicone rubber
• Fire performance: silicone rubber fire-retardant and self-extinguishing
• Pressure relief: directional engineered venting
• Short-circuit capability: up to 300 kA (3EP-G)
• Standards: IEC 60099-4