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Gas-insulated surge arrester AZ

Surge arrester for gas-insulated switchgear for system voltage up to 550 kV

Gas-insulated surge arrester AZ is constructed from a stack of serially connected – extremely non-linear metal-oxide (MO) resistors in a metallic enclosure under pressurized SF6-gas. The special design with high-field blocks allows reduction of the size of the surge arrester, which is an important factor for GIS.

These surge arresters are designed and type-tested according to IEC 62271-203 and IEC 60099-4.

Surge arresters are used to protect the insulation of gas-insulated switchgear as well as the connecting cables and transformers against transient lightning and switching overvoltages.

The surge current monitoring system SAM 3.0 is capable of sensitively registering surges from lightning and switching in combination with total leakage current. The values are shown digitally on an electronic display. It consists of a current sensor with selectable cable lengths and a display device which can be mounted apart from the arrester.


  • Protection of gas-insulated switchgear 
  • Protection of cables 
  • Protection of transformers
  • Protection of hybrid switchgear

Why Hitachi Energy?

  • Over 100 years of experience in overvoltage protection 
  • Local and global Hitachi Energy application support 
  • Proven safe short-circuit current design
  • Design life of more than 30 years
  • Own production of metal-oxide (MO) resistors
  • Compact design due to high-voltage gradient
  • Excellent protection level with low residual voltage
  • High energy absorption capability

Brief performance data

   AZ04E  AZ041  AZ14 AZ32M AZ32H
Hitachi Energy GIS product  ELK-04C ELK-04  ELK-14  ELK-3C  ELK-3 
Class ( IEC 60099-4)  SM-SH SM-SH  SM-SH   SH SH 
Maximum system voltage (Us), kV 145 170 300 420 550 
Continuous voltage through arrester (Uc), kV  58-96 125-173 58-202 211-317 288-374
Rated voltage of arrester (Ur), kV  72-120 156-216 72-252 264-396 360-468 
Phases per enclosure 3 3 1 1

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