Inductive Voltage Transformer EGF

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.

SF6-Insulated Inductive Voltage Transformer EGF, Instrument Transformer

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.

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Features

  • 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

Highlights

SF6-Insulated Inductive Voltage Transformer EGF, Optimally protected density monitor, Instrument Transformer

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 by a special test connection.
  • A solid metal cover protects the density monitor against mechanical damage and direct sunlight.
Excellent protection against moisture, SF6-Insulated Inductive Voltage Transformer EGF, Instrument Transformer

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 drainage area to protect the sealing surfaces of the housings against rain. This significantly reduces gap 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.
SF6-Insulated Inductive Voltage Transformer EGF, Installation-friendly terminal box, Instrument transformer

Installation-friendly 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, spark gaps and sealable covers.
  • By default, all terminal boxes have a flange without holes. Cable glands can be preinstalled on request.

Specifications and Downloads

Technical Specifications

Dimensions

Drawing SF6-Insulated Inductive Voltage Transformer EGF; Instrument Transformer

Technical data

Type EGF

 

 245 300 330 362 420 550
Standard   IEC / IEEE
Highest voltage for equipment kV 245 300 330 363 420 550
Rated power-frequency withstand voltage kV 460 460 460 575 630 680
Rated lightning impulse withstand voltage kV 1050 1050 1175 1175 1425 1550
Frequency Hz 50 / 60
Accuracy class   0.1-3; 3P; 6P
Rated thermal limiting output VT part VA ≤ 3000
Max. simultaneous burden (cl. 0.2) VA ≤ 300
Max. number windings   5
Nominal operating / transport overpressure (20°C) bar 4 / 0.5

Type EGF

 

 

245

 300 330 362 420 550
Height of unit* A mm 3930 3930 4993 4993 5353 6183
Height to primary terminal* B mm 3905 3905 4968 4968 5328 6153
Depth of unit including terminal box

C

mm

 1052 1052 1293 1293 1293 1293
Depth of unit base

D

mm

 730 730 1075 1075 1075 1075
Width of unit base

E

mm

 730 730 1075 1075 1075 1075
Distance between screw holes at base

F

mm

 600 600 900 900 900 900
Min. creepage distance*

 

mm

 6700 7500 8250 9050 10500 13759
Gross weight, approx. *

 

kg

 670 670 805 805 820 850
Gas weight, approx. *   kg 21 21 34 34 36 39

 

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

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