3EJ silicone rubber surge arresters with Cage Design™

Siemens Cage Design™ 3EJ high energy discharge surge arresters offer superior protection against overvoltages in medium-voltage systems.

Siemens 3EJ Cage Design™ surge arresters are ideally suited for the reliable protection of:

• Generators
• Motors
• Arc furnaces
• Arc furnace transformers
• Dry type transformers
• Airfield-lighting systems
• Cable sheath
• Capacitors and capacitor banks
• Converters for drives

The metal oxide varistors (MOV) are enclosed by a cage made of fiber-reinforced plastic (FRP) rods, providing a rigid, reinforced structure ensuring high mechanical strength.

Reliability is guaranteed by the direct molding of the silicone rubber onto the MOV blocks and the FRP rods. This ensures the total embedding of all components free of inclusions and gaps, thus providing an excellent sealing system against any partial discharges or moisture ingress.

In the extremely rare event of the MOV being overloaded, arcing cannot result in a buildup of critical internal pressure, since the MOV are not enclosed in a sealed mechanical shell. The arc can escape directly through the soft silicone housing, leaving the mechanical support structure of the enclosure unharmed. The ejection of internal parts that could damage other equipment nearby is prevented almost completely. Siemens’ innovative Cage Design™ ensures outstanding performance in safety issues.

Silicone rubber is highly hydrophobic and maintains its ability to repel water and any deposits of pollution throughout its entire service life. This results in high tracking and erosion resistance. The silicone rubber housing is self-extinguishing and flame-retardant. These advantages provide maintenance-free and reliable service life for 3EJ surge arresters.

Siemens offers three product lines for the application with high energy discharge capability, which differentiate in the protection level:

• 3EJ2 – for rated voltages up to 54 kV, medium energy discharge capability.
• 3EJ3 – for rated voltages up to 54 kV, high energy discharge capability.
• 3EJ4 – for rated voltages up to 54 kV, very high energy discharge capability.
• 3EJ0 – for rated voltages up to 15 kV, very low residual voltages for protection against switching over voltages.
• 3EJ9 – for rated voltages up to 15 kV, very low residual voltages for protection against switching over voltages.

The proven 3EJ4 is also available in a version for indoor application, which is a Cage Design™ surge arrester offering the same benefits as the version for outdoor application.

The 3EJ0 and 3EJ9 surge arresters have been optimized for the protection against over voltages caused by switching in combination with extreme low residual voltages. The 3EJ0 surge arresters are normally used in cable systems up to 15 kV. For station service systems of power stations and extensive cable systems the 3EJ9 surge arresters are used having a higher absorption capacity and improved protection level.