EGF (245-550) kV


  • SF6-gas insulated
  • Pressure release by using a metal burst-disc
  • Gas density control
  • Only silicone insulator available

Voltage transformers type EGF are used in high voltage substations within the 245-550 kV range. They transform high voltage into standardised, equivalent values for meters, measuring and protection devices.

General description

Voltage transformers type EGF are used in high voltage substations within the 245-550 kV range. They transform high voltage into standardised, equivalent values for meters, measuring and protection devices.

The active section of the voltage transformer is located in the pressureresistant foot housing. The iron core is on earth potential. The secondary windings are directly positioned on the iron core. The secondary windings are passed through an SF6 / air bushing into the terminal box. The high voltage connection is implemented via a short-circuit proof aluminium pipe.

The current distribution along the insulator is optimised by a special layout of the control electrode inside the silicone composite insulator.

The housing components consist of helium-tight, corrosion-resistant cast aluminium. All housing components under pressure are individually typetested according to applicable pressure vessel standards.

The SF6 gas density is monitored by a temperature-compensated gas density monitor with alarm contacts. The special design means the function of the gas density monitor can be checked without dismounting it.

A corrosion-resistant metal rupture disc, protected by a metal cover, is located at the top of the housing and ensures safe pressure relief in case of error.

The generously designed terminal box is equipped with a cover that opens sidewards.

Pure SF6 gas is used for ambient temperatures up to -40°C. The transformer is filled with a mixed gas for lower ambient temperatures up to -60°C.

Advantages of
inductive voltage transformers
  • High operating safety through optimised current distribution in the field-controlled bushing

  • Low weight and high creepage resistance through the use of composite insulators

  • Special iron core provides protection against any ferro resonances
Optimally protected density monitor
Optimally protected
density monitor
  • Precise function is ensured through temperature compensation down to -60°C.

  • The density monitor is equipped with two alarm contacts to signal a pressure loss.

  • The density monitor can be checked without dismounting it via a special test connection.

  • A solid metal cover protects the density monitor against mechanical damage and direct sunlight.
Excellent protection against moisture
Excellent protection
against moisture
  • The inner side of the instrument transformer is protected against moisture by means of special sealing rings.

  • All housings are designed with a drain-age area to protect the sealing surfaces of the housings against rain. This significantly reduces crevice corrosion.

  • The housing elements are connected with special stainless steel screws. They are designed in such a way that no humidity can enter the screw hole.
Installation-friendly terminal box
terminal box
  • The generously sized terminal box with a cover that can be opened sidewards, is secured with captive screws. It can accommodate terminal blocks, fuses, additional auxiliary contacts and sealable covers.

  • The terminal box is equipped as standard with a blind flange. Cable glands can be installed on request.

  • The terminal box has a protected ventilation aperture to prevent condensation.
voltage transformer type EGF
Technical data
voltage transformer type EGF
Type EGF245
StandardIEC / IEEE
Highest voltage for equipmentkV245300330363420550
Rated power-frequency withstand voltagekV460460460575630680
Rated lightning impulse withstand voltagekV105010501175117514251550
FrequencyHz50 / 60
Accuracy class0.1-3; 3P; 6P
Rated thermal limiting outputVA≤  3000
Max. simultaneous burden (cl. 0.2)VA≤ 300
Max. number windings 5
Nominal operating / transport overpressure (20°C)bar4 / 0.5
Type EGF
Height of unit*Amm393039304993499353536183
Height to primary terminal*Bmm390539054968496853286153
Depth of unit including terminal boxCmm105210521293129312931293
Depth of unit baseDmm7427421088108810881088
Width of unit baseEmm7307301075107510751075
Distance between screw holes at baseFmm600600900900900900
Min. creepage distance*mm67007500825090501050013759
Gross weight, approx.*kg670670805805820850
Gas weight, approx.*kg212134343639

*with standard composite silicone insulator, creepage distance 25 mm/kV