Inductive Voltage Transformers
Voltage transformers type EOF are used in high voltage networks within the 24-245 kV range. They transform high voltage in to standardized values for meters, measuring and protections 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 beloows cover.
All metal housings and flanges are made from a special aluminum alloy. These parts can be color coated on request.
All voltage transformers have either a high-quality porcelain or a high-grade silicon composite insulator. Different creepage distances are available according to the different pollution classes, as specified in the standars.
Ther hermetic-sealed housing protects the oil-papre 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 netowork 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 though optimized design
Fine Graded Bushing
- The fine graded bushing is designed to ensure an optimum distribution of the electric filed
- The bushing is fixed in a way that it is short-circuit-safe and secondary arcs are prevented
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 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
- 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.
- By default, all terminal boxes have a flange without hols. Cable glands can be pre-installed on request.
- An additional terminal box can be supplied upon request.