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EOF (24-245) kV

VOLTAGE TRANSFORMERS | OUTDOOR OPERATION

  • Oil-paper insulated
  • Fine-graded bushing
  • Oil level indicator
  • Generously-sized terminal box

Voltage transformers type EOF are used in high voltage networks within the 24-245 kV range. They transform high voltage into standardised values for meters, measuring and protection devices.

 

GENERAL DESCRIPTION

Voltage transformers type EOF are used in high voltage networks within the 24-245 kV range. They transform high voltage into standardised values for meters, measuring and protection devices.

The active part of the voltage transformer is located in the foot housing. The high voltage insulation is implemented in oil-paper technology. To achieve this, a high quality PCB-free mineral oil is used. The fine graded bushing is inside the insulator.

The expansion system is located in the head of the voltage transformer. This unit acts as volume compensation for the oil in case of temperature variations. For voltage transformers of 24-72 kV, a highly flexible, temperature-resistant membrane made from fluoroelastomers (VITON®) is used. Voltage transformers >72 kV have an expansion cell made of stainless steel. The oil level is indicated by a mechanical system in the window of the bellows cover.

All metal housings and flanges are made from a special aluminium alloy. These parts can be colour coated on request.

All voltage transformers have either a high-quality porcelain or a high-grade silicone composite insulator. Different creepage distances are available according to the different pollution classes, as specified in the standards.

The hermetic sealed housing protects the oil-paper insulation against atmospheric influences.

The generously sized terminal box has a cover which can be opened sidewards. This allows easy connection of the secondary cables. The terminal box has a flange without holes by default. Cable glands, circuit diagram and individual safety instructions can be preinstalled on request.

Advantages of
inductive voltage transformers
  • Protection of the secondary winding from transient overvoltages in the high-voltage network through capacitively coupled shielding
     
  • Protection against occurring ferroresonance through low operating inductance in the iron core
     
  • High operating safety as there are no active parts in the insulator
     
  • Minimum oil volume through optimised design

 

HIGHLIGHTS

Fine graded bushing

Fine
graded bushing
  • The fine graded bushing is designed to ensure an optimum distribution of the electric field.
     
  • The bushing is fixed in a way, that it is short-circuit-safe and secondary arcs are prevented.

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

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, surge arrestors, additional auxiliary contacts, spark gaps and sealable covers.
     
  • By default, all terminal boxes have a flange without holes. Cable glands can be preinstalled on request.
     
  • An additional terminal box can be supplied on request.

 

DESIGN

TECHNICAL DATA

voltage transformer type EOF

Type EOF     24 36 72 123 145 170 245
Standard     IEC / IEEE
Highest voltage for equipment   kV 24 36 72.5 123 145 170 245
Rated power-frequency withstand voltage   kV 50 70 140 230 275 325 460
Rated lightning impulse withstand voltage   kV 125 170 325 550 650 750 1050
Frequency   Hz 16.7 / 50 / 60
Accuracy class     0.1-3; 3P; 6P
Rated thermal limiting output   VA ≤ 1500 ≤ 3000
Max. simultaneous burden (cl. 0.2)   VA 200 300
Max. number windings     5
   
Type EOF     24 36 72 123 145 170 245
Height of unit* A mm 1107 1107 1430 2116 2392 2581 3507
Height to primary terminal* B mm 1027 1027 1350 1976 2252 2441 3206
Depth of unit including terminal box C mm 526 526 526 710 710 730 938
Depth of unit base D mm 360 360 360 500 500 500 660
Width of unit base E mm 360 360 360 520 520 520 660
Distance between screw holes at base F mm 310 310 310 450 450 450 600
Min. creepage distance*   mm 950 950 1860 3080 3900 4394 6160
Approximate weight*   kg 115 115 125 305 330 335 350

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



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