Medium-voltage arresters for distribution networks

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Our surge arresters for medium-voltage applications offer reliable overvoltage protection for medium-voltage distribution networks and components for applications up to 72.5 kV.

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Product overview

Overview of our medium-voltage arresters for distribution networks

We offer a wide range of product families for all types of requirements.

It is important to choose the surge arrester based on the application and equipment to be protected:

Surge arresters for distribution networks

Siemens 3EK distribution class surge arresters are ideally suited for the reliable protection of transformers, circuit breakers, medium-voltage switchgear and distribution lines.


Surge arresters with high energy absorption capabilities
In addition to typical distribution class surge arresters, Siemens offers the 3EJ surge arrester product family with higher energy absorption capabilities in combination with a low protection level. The 3EJ medium-voltage surge arresters protect generators, motors, arc furnaces, dry-type transformers, airfield lighting systems, cable sheathing and converters for drives from overvoltage.

Special applications

Siemens offers the 3EQ0 product series for applications that require a surge arrester with a silicone rubber housing and directional pressure relief.
 

Siemens also offers the 3EP-G porcelain housed surge arresters with short-circuit current capability up to 300 kA for the overvoltage protection of generators and motors.

Product families

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Siemens 3EK4 and 3EK7 silicone rubber surge arresters with cage design effectively protect medium-voltage distribution networks from overvoltage.

 

Siemens 3EK4 and 3EK7 cage design surge arresters are ideally suited to provide reliable protection for:

  • Transformers
  • Circuit breakers
  • Medium-voltage switchgear
  • Medium-voltage distribution networks

 

The cage, made of fiberglass-reinforced plastic (FRP) rods, provides a rigid, reinforced structure ensuring high mechanical strength.


The silicone rubber housing is directly molded onto the metal oxide (MO) blocks and the surrounding cage made of FRP rods. This creates a reliable seal that prevents moisture ingress and partial discharges.

The MO resistors are not surrounded by a rigid mechanical coating, which is why no critical increases in pressure can occur in the surge arrester in the extremely rare event of an overload. The arc can escape directly through the soft silicone housing without damaging the mechanical structure. No internal parts are ejected in the process. The innovative Siemens cage design is very secure.

The silicone rubber is highly hydrophobic. This keeps any conductive moisture from forming on the surface, and dirt deposits are rendered harmless as a result of the hydrophobic transfer. Silicone is highly fire-retardant and self-extinguishing in the event of fire. These properties ensure the reliable, maintenance-free operation of 3EK surge arresters.

Siemens offers two types of products for use in distribution networks that differ in terms of mechanical strength:

  • 3EK4 – for rated voltages up to 36 kV, high mechanical strength
  • 3EK7 – for rated voltages up to 60 kV, very high mechanical strength

The proven type 3EK7 surge arrester is also available for indoor use. The 3EK7 surge arrester for indoor use is a cage design surge arrester that offers the same features as the version for outdoor use.

Technical data

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Siemens 3EK8 silicone rubber surge arresters with wrap design effectively protect medium-voltage distribution networks from overvoltage.

 

Siemens 3EK8 wrap design surge arresters are ideally suited to provide reliable protection for:

  • Transformers
  • Circuit breakers
  • Medium-voltage switchgear
  • Medium-voltage distribution networks

 

The silicone rubber housing is directly molded onto the metal oxide (MO) blocks. This creates a reliable seal that prevents moisture ingress and partial discharges.

 

In the extremely rare event of an overload, arcing cannot result in a buildup of critical internal pressure, since the MO resistors are not enclosed in a sealed rigid mechanical shell. The arc can escape directly through the fiberglass wrap and the soft silicone housing without damaging the mechanical structure. No internal parts are ejected in the process.

 

High-temperature vulcanized (HTV) silicone rubber is highly hydrophobic. This keeps any conductive moisture from forming on the surface, and dirt deposits are rendered harmless as a result of the hydrophobic transfer. Silicone is highly fire-retardant and self-extinguishing in the event of fire. These properties ensure the reliable, maintenance-free operation of 3EK8 surge arresters.

 

3EK8 surge arresters can be delivered with the same accessories like 3EK7 surge arresters.

Technical data

 
 
3EK8
Nominal system voltage kV 40.5
Maximum rated voltage kV
36
Maximum continuous operating voltage kV
29
Designation (IEEE)   A
Nominal discharge current kA 10
Thermal charge transfer rating C 0.4
Charge transfer rating C 3.0
Rated short-circuit current kA 20
High current impulse kA 100
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If excess voltage exceeds the energy absorption capacity of a surge arrester, the metal oxide blocks can be damaged and cause the surge arrester to fail. This causes fault current, and an arc forms at both end fittings of the surge arrester. Melted metal can fall to the ground and cause a fire.
 
This is why type 3EK medium-voltage arresters for distribution networks can be equipped with an Arc Protection System (APS), which is installed at both ends of the surge arrester. The APS consists of electrodes nested within each other, which create the power to rotate the arc around the surge arrester housing. This reduces the formation of molten material at the end fittings, dramatically decreasing the risk of forest fires.

 

The APS is available for type 3EK4 and 3EK7 surge arresters. We recommend using surge arresters with APS in especially hot and dry regions with an increased risk of forest fires – like the western United States and South Australia.

The surge arresters can also be equipped with a visible failure message. A red display appears at the bottom end of the surge arrester in the event of a malfunction.

Siemens medium-voltage arresters for distribution networks with APS meet all of the requirements of the Cal Fire Power Line Fire Prevention Field Guide (2008), and have successfully passed all necessary tests. Siemens surge arresters with APS also have a much lower rate of sparks than surge arresters without APS.

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Siemens 3EJ silicone rubber surge arresters with Cage Design™

Siemens 3EJ silicone surge arresters with cage design are ideally suited for reliable protection against overvoltages in medium-voltage distribution networks.

Siemens 3EJ cage design surge arresters are ideally suited to provide reliable protection for:

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


The cage, made of fiberglass-reinforced plastic (FRP) rods, provides a rigid, reinforced structure ensuring high mechanical strength.

The silicone rubber housing is directly molded onto the metal oxide (MO) blocks and the surrounding cage made of FRP rods. This creates a reliable seal that prevents moisture ingress and partial discharges.

 

The MO resistors are not surrounded by a rigid mechanical coating, which is why no critical increases in pressure can occur in the surge arrester in the extremely rare event of an overload. The arc can escape directly through the soft silicone housing without damaging the mechanical structure. No internal parts are ejected in the process. The innovative Siemens cage design is very secure.


The silicone rubber is highly hydrophobic. This keeps any conductive moisture from forming on the surface, and dirt deposits are rendered harmless as a result of the hydrophobic transfer. Silicone is highly fire-retardant and self-extinguishing in the event of fire.  These properties ensure the reliable, maintenance-free operation of 3EJ surge arresters.

 

Siemens offers five product types for applications with high energy absorption capacities that vary in terms of the protection level:

  • 3EJ2 – for rated voltages up to 54 kV, medium energy absorption capability
  • 3EJ3 – for rated voltages up to 54 kV, high energy absorption capability
  • 3EJ4 – for rated voltages up to 54 kV, very high energy absorption capability
  • 3EJ0 – for rated voltages up to 15 kV, very low protection level, for protection against overvoltages
  • 3EJ9 – for rated voltages up to 15 kV, very low residual voltage, for protection against overvoltages


The proven type 3EJ4 surge arrester is also available for indoor use. The 3EJ4 surge arrester for indoor use is a cage design surge arrester that offers the same features as the version for outdoor use.

The 3EJ0 and 3EJ9 surge arresters are optimized with an extremely low protection level for protection against overvoltages. The type 3EJ0 is used in cable networks with up to 15 kV. Type 3EJ9 surge arresters should be used for power plants and extensive cable networks. These have a higher energy absorption capacity and a better protection level.

Technical data

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We offer the 3EQ0 for rated voltages of up to 45 kV for applications in which a surge arrester in silicone housing is required in combination with directional pressure relief.


The surge arrester with the composite hollow core design uses silicone and fiberglass-reinforced plastic (FRP) as housing materials. The direct molding of the silicone onto the FRP hollow core ensures reliability, while an excellent special sealing of the flanges at both ends of the surge arrester effectively prevents partial discharges and moisture ingress. This guarantees decades of trouble-free operation.

The combination of silicone rubber and the fiberglass-reinforced hollow core also allows for outstanding mechanical stability.

 

The surge arrester with the composite hollow core design provides a very high degree of safety: In the event of an overload or the extremely rare case of an arrester short circuit, the arc escapes directly through directional pressure relief devices.


The surge arrester can be oriented to minimize the risk of damage to facilities and injuries to people nearby. Internal parts are not ejected, and the housing does not break.
 

Siemens 3EQ surge arresters with silicone housing and a composite hollow core design are ideally suited for the reliable protection of:

-         Generators

-         Motors

-         Arc furnaces

-         Dry-type transformers

-         Airfield lighting systems

-         Cable sheathing

-         Capacitors and capacitor banks

-         Converters for drives

Technical data

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In addition to providing maximum protection against overvoltages, Siemens’ 3EP porcelain surge arresters feature a specially developed directional pressure relief system. In the event of an overload, the arc can escape directly through the directional pressure relief device. Strong, high-quality porcelain prevents pressure from building inside and internal parts from being rejected. This reduces, even minimizes the risk of damage to facilities or injuries to people in nearby.

Siemens offers the 3EP-G porcelain surge arrester, which has a short circuit current of up to 300 kA. It is ideal for overvoltage protection for generators and motors that require a very high short circuit current.  

 

The excellent sealing system on the 3EP-G surge arrester effectively prevents moisture ingress and partial discharges, guaranteeing decades of trouble-free operation. The use of non-porous sulfur cement instead of corrosive Portland cement protects the metal oxide blocks and prevents the effects of aging.


The metal oxide blocks in the 3EP-G surge arrester are enclosed in a rigid, reinforced structure made of fiberglass-reinforced plastic (FRP) rods.

Siemens type 3EP-G porcelain surge arresters are ideally suited for the reliable protection of:

-         Generators

-         Motors

-         Arc furnaces

-         Dry-type transformers

-         Airfield lighting systems

-         Cable sheathing

-         Capacitors and capacitor banks

-         Converters for drives

Technical data

Maximum values
 
 
3EP-G
Highest voltage of the system
  kV 72.5
Maximum rated voltage
  kV 51
Maximum continuous voltage
  kV 40.8
Surge arrester class
Nominal discharge current Thermal energy rating
Charge transfer rating
 
  kA kJ / kVr
C  
SM 10 7.0 2.0 X
SH 20 10 2.8 X
Rated short-circuit current   kA 300
High current impulse
  kA 100

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You can find more details on our medium-voltage arresters for distribution networks and information about our services here.

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Testing laboratories at Schaltwerk Berlin

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Testing laboratories at Schaltwerk Berlin
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Technical simulations

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Technical simulations

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