sf6 insulated current transformers 110..750 kV

The instrument high-voltage current transformers (CTs) of the LVQB series are designed to transmit the signal of measuring information devices for the devices, automation, alarm and control of electrical current circuits from 110 to 750 kV with a frequency of 50 or 60 Hz. The principle of action of current transformers is based on the phenomenon of electromagnetic induction. Current transformers (CTs) are designed for the life of at least 30 years (and even more with proper operation). Internal gas isolation (SF6) is hermetically isolated from air, and all external parts are made of corrosion-resistant material.

By design, base-type instrument transformers are located with upper windings in a metal casing. The high-voltage windings are housed in a metal casing mounted on the top of the transformer's insulating column, and SF6 gas is used as the internal insulating medium. Current transformers can have up to eight secondary windings, for measuring and protection, depending on the load and the protection accuracy class. The primary winding is connected to the inputs passing through the aluminum housing; the number of turns of the first winding is changed using special metal jumpers. The secondary terminals of the windings are located in a contact box mounted on the base of the transformer. To prevent unauthorized access to secondary wires, the terminal box cover, located with a contact inside the box, is sealed. For safety reasons, transformers are equipped with overpressure relief valves, which are activated when the pressure reaches 0.65 MPa (0.8 MPa for voltages of 500 kV and above). To indicate the SF6 gas pressure in transformers, two-channel pressure gauges are provided. One channel provides a signal if refueling is necessary, the other, in the event of an extreme decrease in pressure, sends a signal to trigger the protection.
External insulation, depending on the customer’s wishes, can be porcelain or silicone (polymer).


  • Rated voltage from 110 to 765 kV
  • Rated current up to 8000 A
  • Rated short-time thermal current (Ith) up to 63 kA/1 or 3 sec.
  • Rated dynamic withstand current (Idyn) up to 160 kA
  • Number of secondary windings up to 8
  • Winding accuracy class for measurement 0.2; 0.2S; 0.5; 0.5S; 1; 3;
  • Winding accuracy class for protection 5P;10P
  • Switching the transformation ratio on primary or secondary outputs.
  • Oil expansion with stainless steel bellows
  • External insulation porcelain or polymer
  • SF6 level indicator
  • Ambient conditions: temperature from -60° to +55°
  • Compliance with IEC and IEEE standards or equivalent standards
  • Possibility of manufacturing transformers for direct (DC) voltage.


  • Special protection accuracy classes: TPS, TPX, TPY, TPZ, PR
  • Affordable High and Extended Range Accuracy (ERCT) Design
  • Possibility of manufacturing transformers for direct (DC) voltage.
  • Consistent accuracy over the entire service life
  • No oil
  • High fire and explosion safety

The description contains the characteristics of transformers that are produced in series. By agreement with the customer, it is possible to manufacture non-standard transformers.

750kV 500kV 400kV 330kV 275kV 230kV 220kV 161kV 150kV 138kV 132kV 115kV 110kV 88kV 69kV 66kV 63kV 46kV 33kV High voltage SF6 gas insulated current transformer,  high voltage Current transformer  HV SF6 CT.