VariSTAR polymer-housed surge arresters are gapless arresters that are composed of MOV (Metal Oxide Varistor) elements. VariSTAR surge arresters from Cooper Power Systems are available in distribution- and station-class as well as in elbow arrester products.

In a porcelain body our VariSTAR line provides highly reliable service operation to meet a wide range of service applications. Porcelain housed VariSTAR distribution arresters are available in Normal Duty (type AZS) and Heavy Duty Type (type AZL). Both surge arrester design types have been certified to the latest revision of standard ANSI/IEEE C62.11. Arrester duty-cycle ratings range from 3 to 36 kV.


  • The UltraSIL silicone rubber housing has undergone a wide range of design tests to determine the optimum shed configuration. In addition, long term environmental testing has verified the lifetime superiority of UltraSIL silicone rubber when compared to other polymeric insulating materials.
  • Independent laboratory tests have verified the superiority of silicone rubber in terms of hydrophobicity, resistance to UV and surface tracking performance in contaminated environments, chemical inertness, temperature stability and other key insulating properties.
  • UltraSIL silicone rubber will not support biological growth (algae and mildew) and is non-flammable.
  • A ground lead disconnector is optionally available for use on systems having 20A or more of available fault current. The disconnector will sense and disconnect the ground terminal in the unlikely event of arrester failure, preventing a permanent system short circuit. A disconnector that has operated gives a visual indication of internal arrester damage and the need for arrester replacement.


  • The wet-process porcelain housing features an alternating shed design that provides excellent resistance to the effects of atmospheric housing contamination.
  • VariSTAR arresters are a totally gapless MOV design. Gapless construction makes a significant contribution to the performance of arresters through the elimination of gap reseal as a consideration associated with the discharge of switching surge currents.
  • The end fittings and porcelain housing of each arrester unit are sealed and tested by means of a sensitive helium mass spectrometer; this assures that the quality and insulation protection provided by the arrester is never compromised over its lifetime by the entrance of moisture.
  • High Cantilever strength assures mechanical integrity
  • The unit end castings are of a corrosion-resistant aluminum alloy configured for interchangeable mounting with other manufacturers’ arresters for ease in upgrading to the VariSTAR arrester technology.