Class II surge arrester 3EK7 séries

high-energyfor substationsfor transient current protection

Overview
Medium-voltage surge arresters are essential for safeguarding electrical equipment from damaging overvoltages caused by lightning strikes, switching operations and other transient events. Siemens Energy offers a portfolio of medium-voltage surge arresters designed to provide reliable overvoltage protection for distribution networks and critical electrical equipment up to 72.5 kV. Selecting the appropriate surge arrester depends on the application and equipment to be protected.

Key functions and features

• Wide voltage range: Suitable for applications up to 72.5 kV, accommodating diverse medium-voltage needs.
• High energy absorption: Provides robust protection for sensitive and high-demand equipment, ensuring operational reliability.
• Advanced housing materials: Available in silicone rubber (polymer) and porcelain, offering environmental resilience and safety.
• Reliable pressure relief: Minimizes risk of damage and injury during overloads, enabling safe venting of arcs without ejecting internal parts.
• Maintenance-free operation: Hydrophobic high-temperature vulcanized silicone surfaces prevent moisture-related issues, ensuring long-term reliability.
• Compliance: Products meet IEC 60099-4 standards, guaranteeing quality and performance.

Siemens Energy product families and design highlights

• 3EK distribution class surge arresters: Ideal for protecting transformers, circuit breakers, medium-voltage switchgear and distribution lines. Silicone rubber designs include:
  • 3EK7 with Cage Design™: Fiberglass-reinforced plastic (FRP) cage for mechanical strength; silicone rubber molded directly on metal oxide (MO) blocks to prevent moisture ingress and partial discharges; highly hydrophobic and fire-retardant for maintenance-free operation.
  • 3EK8 wrap design: Silicone rubber directly molded onto MO blocks with a fiberglass wrap, allowing arc escape without mechanical damage; excellent moisture resistance and self-extinguishing properties.
• 3EJ family (high energy absorption): Offers higher energy absorption capabilities with low protection levels. Suitable for generators, motors, arc furnaces, dry-type transformers, airfield lighting, cable sheathing and converters. Product types include:
  • 3EJ2: rated voltages up to 54 kV, medium energy absorption capability.
  • 3EJ3: rated voltages up to 54 kV, high energy absorption capability.
  • 3EJ4: rated voltages up to 54 kV, very high energy absorption capability; also available in an indoor version.
  • 3EJ0: optimized for rated voltages up to 15 kV, very low protection level for cable networks.
  • 3EJ9: tailored for rated voltages up to 15 kV, very low residual voltage, recommended for power plants and extensive cable networks.
• 3EH4 plug-in surge arresters: Plug-and-socket connections compliant with EN 50180 / EN 50181 standards; suitable for voltages up to 52.5 kV; rugged design for high power handling and long life; connector sizes available for inner cone systems and arrester class DH.
• 3EP-G porcelain surge arresters: Porcelain-housed arresters with directional pressure relief systems and short-circuit current capability up to 300 kA; ideal for generator and motor protection requiring very high short-circuit current capability; excellent sealing prevents moisture ingress and aging effects.

Technical highlights and benefits
Siemens Energy surge arresters combine silicone rubber and porcelain housings to deliver benefits in voltage range, mechanical strength and safety. Hydrophobic high-temperature vulcanized silicone rubber prevents moisture and dirt accumulation, is fire-retardant and self-extinguishing, and polymer housings offer superior pollution resistance and lighter weight compared to porcelain.

Technical summary (table)
Feature | Description
Voltage range | Up to 72.5 kV
Housing materials | Silicone rubber (3EK, 3EJ), porcelain (3EP-G)
Mechanical strength | Fiberglass-reinforced plastic cages or wraps for structural integrity
Pressure relief | Pressure relief to safely vent arcs without ejecting internal parts
Hydrophobicity | High-temperature vulcanized silicone rubber prevents moisture and dirt accumulation
Fire safety | Silicone rubber is fire-retardant and self-extinguishing
Short-circuit current capability | Up to 300 kA (3EP-G porcelain arresters)

Applications

• Distribution networks: Protecting transformers, circuit breakers and distribution lines from transient overvoltages.
• Industrial facilities: Safeguarding sensitive electrical equipment in manufacturing and processing facilities.
• Renewable energy systems: Ensuring reliable operation of wind, solar and other renewable power installations.
• Utilities: Enhancing grid reliability and reducing outage risks by limiting surge-induced equipment failures.

Why choose Siemens Energy medium-voltage surge arresters?

• Wide product range and advanced housing technologies tailored to diverse applications.
• High energy absorption capabilities to protect against severe transient overvoltages.
• Innovative pressure relief systems engineered to minimize damage and ensure personnel safety.
• Compliance with international standards (IEC 60099-4) guaranteeing quality and performance.

Technical specifications

• Voltage rating: up to 72.5 kV
• Housing materials: silicone rubber (polymer) and porcelain
• Series / types: 3EK (including 3EK7 Cage Design™ and 3EK8 wrap design), 3EJ (3EJ2, 3EJ3, 3EJ4, 3EJ0, 3EJ9), 3EH4 (plug-in), 3EP-G (porcelain)
• Short-circuit current capability (3EP-G): up to 300 kA
• Standards: IEC 60099-4; plug-in variants compliant with EN 50180 / EN 50181
• Mechanical reinforcement: FRP cages or fiberglass wraps
• Hydrophobic and fire-retardant silicone rubber; maintenance-free external design
• Typical protected equipment: transformers, switchgear, generators, motors, capacitors, cable networks, arc furnaces