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Current Transformer TG (72.5 - 800 kV)

Gas-insulated instrument transformer for enhanced safety and reliability

TG is a gas-insulated high voltage current transformer based on a top-core design, able to withstand current up to 4,000 A and designed for voltages from 72.5 to 800 kV. Primary and secondary windings are located inside the upper part of the transformer. Some important features of the product are:

  • Suitable for both metering and protection 
  • Short primary conductor with low thermal losses suitable for high rated current
  • Magnetic cores made of laminated steel with oriented grain and a high level of permeability
  • Windings made of electrolytic copper
  • Safety margin for normal wind loads, stress from conductors and seismic forces
  • Remote control of the internal insulation level by means of pressure gauge provided with an alarm threshold and lock threshold
  • A pressure relief device protects the apparatus from internal overpressure


  • Revenue metering
  • Protective relaying
  • System control and indication of power flow

Why Hitachi Energy?

For the TG combination of  SF6 gas insulation and with a composite insulator, offers several advantages:

  • Explosion-proof design
  • Non-flammable
  • Absence of partial discharge
  • Dielectric mean not subjected to aging
  • Higher performance in very heavily polluted environments
  • Maintenance-free
  • Life cycle of 30 years

Brief performance data

TG Current transformer  
Installation Outdoor
Design Self-standing top-core type
Insulation SF6 gas
Highest voltage for equipment 72.5 - 800 kV
Max primary current Up to 4.000 A
Short-circuit current Up to 63 kA
Insulators Porcelain or composite
Short time power frequency withstand voltage Up to 975 kV
SF6 leakage Less than 0.1% for year
Ambient temperature -50 ºC to +40 ºC (Standard)
Pollution level IV (very heavy)
Accuracy Meets all IEC and IEEE metering and protection classes

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