We offer a wide range of surge protective devices with different circuit design and construction to cover the different application needs. The overview below provides a comparison of fundamental characteristics for the priciple selection related to the operating conditions and protection needs.


Varistor based SPDs:

  • NFC No Follow Current®
  • very short response time (ta): ≤ 25 ns;
  • very good voltage protection level even at certain impulse overcurrent;
  • high impulse current rating: (Iimp) up to 25 kA/pole, 10/350 μs; (Imax) up to 100 kA/pole 8/20 μs.

The wide range of limiting SPDs with NFC No Follow Current® technology allows optimum protection in most applications, also in large installations, where SPDs often operate independent from each other, and where reliable protection and high performance are required.

Combined Voltage Limiting and Switching SPD with varistor and GDT connected in series:

  • NFC No Follow Current® as a result of the combination;
  • short response time (ta): ≤ 100 ns;
  • good voltage protection level;
  • no leakage currents.

Combined SPDs make use of GDT and varistor elements, with voltage switching and with voltage limiting function. In our production range, these SPDs have been optimized for those applications where no really high discharge capability is required, as for example residential applications.

Type IA - Voltage Switching Spark gap based SPDs with trigger technology:

  • high impulse current rating: (Iimp) 25 kA/pole 10/350 μs; 100 kA/4 poles 10/350 μs);
  • short response time (ta): ≤ 100 ns;
  • good voltage protection level;
  • no leakage currents.

SPDs with spark gap and trigger technology are intended for primary protection applications where the prospective short circuit current of the power distribution system at the installation point of the SPDs is lower than or equal to Ifi and for installations where coordinated SPDs with very short response time are provided for secondary protection. A typical application is e.g. in a TT system of a medium plant size comprising a main distribution board feeding first and second level subdistribution boards.

Type I - Voltage Switching GDT based SPDs:

  • the typical application for this device is in the N-PE mode of protection in TT;
  • distribution systems (1+1 or 3 + 1 construction, connection type CT 2 according to HD 60364-5-534);
  • high impulse current rating (Iimp) and (Imax) up to 100 kA, 10/350 μs.

Type G - Isolating Spark Gap ISG SPDs:

These devices are used to indirectly connect an LPS to nearby metal structures which cannot be directly connect for functional reasons.

  • Monolithic explosion proof protection;
  • High protection of the insulation resistance versus the injected current;
  • High discharge capability (Iimp).

Combined Voltage Limiting and Switching SPD plus Filter with varistor and GDT comprising an additional filter:

  • effective noise level attenuation by use of additional high frequency bandpass filters;
  • high level interference protection for sensitive equipment with limited resistivity and immunity characteristics;
  • high discharge capabilty (combination wave test at Uoc 10 kV 1,2/50 μs, Icw 5 kA 8/20 µs).

Combined SPDs with additional filter are used where high continuity of service is required like data centers, DCS (distributed control systems), etc.. These SPDs do not only protect against transients due to lightning, but also against high frequency conducted interferences. They are applied where Electromagnetic Compatibility (EMC) is an issue and requires improvement of the system immunity.

Protection boxes with an IP65 enclosure which provide a compact and preinstalled solution for applications in Power Centers.

CPs are fork-type busbars with 2 up to 8 connection points. Typical application: to provide a common PE connection for several SPDs.

SPD LED Light Protection Systems. A ready to install assembly of a voltage limiting and a voltage switching SPD providing two modes of protection.

SPDs for Signalling, telecommunication and data transmission.
These SPDs are connected, on linea, in series with low resistivity electronic equipments, like analog interfaces and data networks.

Specific SPDs with coaxial connectors, for protecting TV switchboards, satellite antenna or wideband transmission equipment and remote systems. Particularly suitable for applications with long coaxial cables which are exposed to electromagnetic interference.

Surge Arresters for high voltage systems (HV) with typical applications: protection of transformers, switchgears and transmission lines in HV systems.

  • Surge Arresters with silicone rubber housing providing big internal and external creepage distances suitable for all applications with high level of pollution.
  • Surge Arresters available with disconnector device, which is activated by and increase in internal preassure with a reliable operating mechanisc and stable characteristic even over long time.
  • Additional impulse counter and impulse counter + measurement for indication of total leakage current (internal and external dispersion).
  • Surge Arresters with a higher thermal energy rating than 4,5 kJ/kV are available upon request.

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