Combined instrument transformer for HV applications

Abstract

A combined instrument transformer for HV applications which includes a current instrument transformer CT, having a current transformer core and a current transformer primary duct fitted into the current transformer core, and a voltage instrument transformer VT, having a voltage transformer core and voltage transformer windings fitted around at least a portion of the voltage transformer core. The current instrument transformer and the voltage instrument transformer are housed in a common internal volume of a single enclosure, the internal volume being delimited by a lateral wall, a base disk insulator and a substantially planar cover.

Claims

1. A combined instrument transformer for HV applications, comprises: a current instrument transformer CT, having a current transformer core and a current transformer primary duct fitted into said current transformer core; and a voltage instrument transformer VT, having a voltage transformer core and voltage transformer windings fitted around at least a portion of said voltage transformer core, wherein the current instrument transformer CT and the voltage instrument transformer VT are housed in a common internal volume of a single enclosure, and wherein the common internal volume is delimited by a lateral wall, a support device and a planar cover.

2. The combined instrument transformer for HV applications according to claim 1, wherein the enclosure is vertically mounted on a hollow core insulator or a ceramic insulator and a basement and in that the support device is a base disk insulator.

3. The combined instrument transformer for HV applications according to claim 1, wherein the enclosure comprises first and second primary terminals for connection to a HV line and electrically connected to the current transformer primary duct and in that the support device is a base disk insulator.

4. The combined instrument transformer for HV applications according to claim 2, wherein the base disk insulator separates said internal volume from the hollow core insulator or ceramic insulator.

5. The combined instrument transformer for HV applications according to claim 1, wherein the voltage instrument transformer VT comprises VT secondary wires connected to the voltage transformer windings, and wherein the current instrument transformer CT comprises CT secondary wires connected to the current transformer core.

6. The combined instrument transformer for HV applications according to claim 1, wherein the current transformer core is shielded into a metallic plate shell.

7. The combined instrument transformer for HV applications according to claim 1, wherein the current transformer core is in contact with and supported from below by the base disk insulator.

8. The combined instrument transformer for HV applications according to claim 1, wherein the planar cover is in contact with and arranged above the voltage transformer core.

9. The combined instrument transformer for HV applications according to claim 1, wherein the planar cover is in contact with and arranged above the voltage transformer windings.

10. The combined instrument transformer for HV applications according to claim 1, wherein the hollow core insulator or ceramic insulator comprises a secondary duct running inside the hollow core insulator or ceramic insulator from the base disk insulator to the basement, the VT secondary wires and the CT secondary wires running inside the secondary duct.

11. The combined instrument transformer for HV applications according to claim 5, wherein the VT secondary wires are fitted into a metallic plate shell.

12. The combined instrument transformer for HV applications according to claim 2, wherein the enclosure comprises first and second primary terminals for connection to a HV line and electrically connected to the current transformer primary duct and in that the support device is a base disk insulator.

13. The combined instrument transformer for HV applications according to claim 3, wherein the base disk insulator separates the internal volume from the hollow core insulator or ceramic insulator.

14. The combined instrument transformer for HV applications according to claim 12, wherein the base disk insulator separates the internal volume from said hollow core insulator or ceramic insulator.

15. The combined instrument transformer for HV applications according to claim 2, wherein the current transformer core is shielded into a metallic plate shell.

16. The combined instrument transformer for HV applications according to claim 3, wherein the current transformer core is in contact with and supported from below by the base disk insulator.

17. The combined instrument transformer for HV applications according to claim 2, wherein said the planar cover is in contact with and arranged to support the voltage transformer windings.

18. The combined instrument transformer for HV applications according to claim 2, wherein the hollow core insulator or ceramic insulator comprises a secondary duct running inside the hollow core insulator or ceramic insulator from the base disk insulator to the basement, wherein VT secondary wires and CT secondary wires run inside the secondary duct.

19. The combined instrument transformer for HV applications according to claim 6, wherein VT secondary wires are fitted into the metallic plate shell.

20. The combined instrument transformer for HV applications according to claim 1, wherein the planar cover is in contact with and arranged to support the voltage transformer windings are supported from the above by the planar cover; wherein the enclosure is vertically mounted on a hollow core insulator or a ceramic insulator and a basement and in that the support device is a base disk insulator wherein the hollow core insulator or ceramic insulator comprises a secondary duct running inside the hollow core insulator or ceramic insulator from the base disk insulator to the basement, the VT secondary wires and the CT secondary wires running inside the secondary duct; and wherein the VT secondary wires are fitted into the metallic plate shell.

Description

(1) Further features and advantages of the present invention will be more clear from the description of preferred but not exclusive embodiments of a combined instrument transformer for HV applications according to the invention, shown by way of examples in the accompanying drawings, wherein:

(2) FIG. 1 is a front view of an embodiment of a combined instrument transformer for HV applications according to the present invention;

(3) FIG. 2 is a section view of an embodiment of a combined instrument transformer for HV applications according to the present invention;

(4) FIG. 3 is a perspective view in section of an embodiment of a combined instrument transformer for HV applications according to the present invention.

(5) With reference to the attached figures, a combined instrument transformer for HV applications according to the present invention—designated with the reference numeral 1—in its more general definition comprises a current instrument transformer CT 2 and a voltage instrument transformer VT 3.

(6) The current instrument transformer CT 2 typically comprises a current transformer core 21 and a current transformer primary duct 22 which is fitted into said current transformer core 21.

(7) Similarly, the a voltage instrument transformer VT 3 typically comprises a voltage transformer core 31 and voltage transformer windings 32 which are fitted around at least a portion of said voltage transformer core 31

(8) One of the characterizing features of the combined instrument transformer 1 for HV applications of the present invention is given by the fact that said current instrument transformer CT 2 and said voltage instrument transformer VT 3 are conveniently housed in a common internal volume 41 of a single enclosure 4.

(9) As shown in the attached figures, said common internal volume 41 is delimited by a lateral wall 42, a base disk insulator 43 and a substantially planar cover 44.

(10) Thus it is clear from the attached figures that the overall space of the single enclosure 4 is much less than the space and volume normally occupied by the two enclosures normally needed in the combined instrument transformer of know type for separately housing the current instrument transformer CT and the voltage instrument transformer VT.

(11) It is also clear that in the combined instrument transformer 1 of the present invention, the number of sealing is greatly reduced with respect to the conventional instrument transformers, only one disk insulator 43 being for instance present in the embodiment shown in the attached figures.

(12) The combined instrument transformer 1 for HV applications of the present invention can be vertically mounted on a hollow core insulator 5 and a basement 6 as shown in the attached figures.

(13) In particular, FIG. 1 shows an overview of an embodiment of the combined instrument transformer 1 according to the present invention. According to such embodiment, the combined instrument transformer 1 is based on top core design, meaning that the magnetic cores of the current instrument transformer CT 2 and voltage instrument transformer VT 3 are located at the top, where they are fit into the single enclosure 4, and are connected to the HV line through the first 411 and second 412 primary terminals.

(14) The top portion is supported by a hollow core insulator 5. The basement 6 at the bottom of the equipment provides fixation points for a support structure, as well as connection of instrumentation and outlet and terminals for secondary cables.

(15) As previously said, in the embodiment of the combined instrument transformer for HV applications shown ion the attached figures, only one insulator 43 is needed, said insulator 43 being positioned at the base of the enclosure 4 and separating the internal volume 41 of the enclosure 4 from said hollow core insulator 5.

(16) In the combined instrument transformer 1 of the present invention, the voltage instrument transformer VT 3 conveniently comprise VT secondary wires 35 which are connected to said voltage transformer windings 32.

(17) Also, the current instrument transformer CT 2 conveniently comprises CT secondary wires 25 which are connected to said current transformer core 21.

(18) Preferably, as shown in the attached figures, said current transformer core 21 is shielded into a metallic plate shell 28 and is supported from below by said base disk insulator 43. In such a case, also said VT secondary wires 35 can be conveniently fitted into said metallic plate shell 28.

(19) Also, in the embodiment of the combined instrument transformer 1 for HV applications shown in FIGS. 2 and 3, said voltage transformer core 31 is supported form the above by said substantially planar cover 44.

(20) Similarly, also the voltage transformer windings 32 can be conveniently supported form the above by the substantially planar cover 44.

(21) According to a preferred embodiment of the combined instrument transformer 1 for HV applications, the hollow core insulator 5 comprises a secondary duct 55 running inside said hollow core insulator 5 from said base disk insulator 43 to said basement 6, said VT secondary wires 35 and said CT secondary wires 25 running inside said secondary duct 55.

(22) In practice, with reference to FIG. 2, the voltage transformer core 31 and the voltage transformer windings 32 are positioned into the said single enclosure 4, together with the current instrument transformer CT 2.

(23) The current transformer primary duct 22 is connected to the enclosure 4 and the first 411 and second 412 primary terminals and is fitted into the current transformer core 21, with one or more turns. The VT secondary wires 35 and the CT secondary wires 25 are fitted together into the secondary duct 55, running through the hollow core insulator 5, down to the basement 6.

(24) With reference also to FIG. 3, the voltage transformer core 31 and the voltage transformer windings 32 are supported from the above by the substantially planar cover 44 which is mounted on the top of the single enclosure 4, while the current transformer core 21 is supported from below by said base disk insulator 43 which separates the internal volume 41 of the enclosure 4 from said hollow core insulator 5.

(25) The current transformer core 21 is shielded into a metallic plate shell 28. The VT secondary wires 35 of the voltage instrument transformer, which are connected to the voltage transformer windings 32, are also fitted into the said Current Transformer metallic plate shell 28, in order to reach the secondary duct 55, passing through the base disk insulator 43 together with the CT secondary wires 25 of the Current Transformer.

(26) From the above-description it is clear that the combined instrument transformer 1 for HV applications of the present invention fully achieved the intended aim and purposes, solving the prior art problems.

(27) In particular, thanks to the use of a single enclosure housing both the current instrument transformer and the voltage instrument transformer CT, the overall dimensions of the equipment are reduced.

(28) Moreover, the number of components, in particular the number of expensive sealing is greatly reduced with respect to the conventional instrument transformers, only one disk insulator being for instance present in the embodiment shown in the attached figures.

(29) It is also worth noting that the unconventional design of the combined instrument transformer of the present invention, in which the voltage transformer core 31 and the voltage transformer windings 32 are supported from the above by the substantially planar cover 44, while the while the current transformer core 21 is supported from below by the base disk insulator 43 allows reducing the number of components, and thereby the costs of the combined instrument transformer.

(30) In practice, in the combined instrument transformer some of the components can have a double function, e.g.: the substantially planar cover 44 closes the internal space 41 of the enclosure 4 from the top and at the same time supports from the above the voltage transformer core 31 and the voltage transformer windings 32; similarly, the base disk insulator 43 separates the internal space 41 of the enclosure 4 from the hollow insulator 5 and at the same time support the current transformer core 21 from below.

(31) Several variations can be made to the combined instrument transformer for HV applications thus conceived, all falling within the scope of the attached claims. In practice, the materials used and the contingent dimensions and shapes can be any, according to requirements and to the state of the art.