HV apparatus and a method of manufacturing such apparatus

Abstract

The present invention refers to HV apparatus, in particular a HV dry current transformer, insulated with an insulating gel, or a voltage transformer, insulated with an insulating gel. The dry HV current transformer comprises at least two electrically conductive elements i.e. a head transformer cover, a head housing base, a core casing and a primary conductor. In the dry HV current transformer at least one of the electrically conductive elements has a coating made of solid insulating material separating the surface of the conductive elements from the insulating gel and adapted for limiting the electron emission from the conductive elements into the insulating gel. The voltage transformer comprises a bottom external housing, a bottom support flange, a core. In the voltage transformer at least one of the electrically conductive elements has a coating made of solid insulating material separating the surface of the conductive elements from the insulating gel and adapted for limiting the electron emission from the conductive elements into the insulating gel.

Claims

1. A high voltage (HV) apparatus in a form of a HV current transformer comprising: electrically conductive elements comprising an electrically conductive head transformer cover, an electrically conductive head housing base, and an electrically conductive core casing with a core set therein; electric insulation material comprising an insulating gel filling enclosed space between at least two of the electrically conductive elements; wherein at least one of the electrically conductive elements has a coating thereon made of solid insulating material separating the surface of the conductive element from the insulating gel and is adapted for limiting the electron emission from the conductive elements into the insulating gel; and wherein the coating is placed on an internal surface of the head transformer cover, and the coating is placed on an internal surface of the head housing base.

2. The apparatus according to claim 1, wherein the coating is placed on an external surface of the core casing.

3. The apparatus according to claim 1, wherein the core casing is filled with a light filler material placed between the core and a part of a lead tube which is sealed by means of the secondary lead plug.

4. The apparatus according to claim 1, wherein the coating is placed on an external surface of the primary conductor.

5. The apparatus according to claim 1, which further comprises a head transformer housing equipped with an inlet channel placed in the head housing base and with an outlet channel placed in the top of the head transformer housing.

6. The apparatus according to claim 5, wherein a length of the channels and is bigger than their diameters.

7. The apparatus according to claim 1, which further comprises a head transformer housing equipped with an inlet channel placed in the head housing base and with an outlet channel placed in the top of the head transformer housing.

8. The apparatus according to claim 2, which further comprises a head transformer housing equipped with an inlet channel placed in the head housing base and with an outlet channel placed in the top of the head transformer housing.

9. The apparatus according to claim 3, which further comprises a head transformer housing equipped with an inlet channel placed in the head housing base and with an outlet channel placed in the top of the head transformer housing.

10. The apparatus according to claim 4, which further comprises a head transformer housing equipped with an inlet channel placed in the head housing base and with an outlet channel placed in the top of the head transformer housing.

11. A high voltage current transformer comprising: an electrically conductive core casing; a core set within the electrically conductive core casing; an electrically conductive head housing cover surrounding the electrically conductive core casing; a primary conductor extending through the electrically conductive head housing cover and the electrically conductive core casing; an insulating gel that fills a space between the electrically conductive core casing and the electrically conductive head housing cover; and a coating comprising a solid insulating material on an outer surface of the electrically conductive core casing, wherein the coating is between the electrically conductive core casing and the insulating gel.

12. The high voltage current transformer of claim 11, wherein the coating is adapted for limiting the electron emission from the electrically conductive core casing into the insulating gel.

13. The high voltage current transformer of claim 11, wherein the coating is also provided on an internal surface of the head housing cover.

14. The high voltage current transformer of claim 11, wherein the coating is also provided on an external surface of the primary conductor.

15. The apparatus according to claim 1, wherein the coating comprises a spray coating.

16. The high voltage current transformer of claim 11, wherein the coating comprises a spray coating.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The present invention is depicted in an exemplary embodiment on the drawing, where

(2) FIG. 1 presents a first embodiment of the invention in the form of current transformer in a cross-section;

(3) FIG. 2 presents an arrangement of solid insulation material coating for the embodiment presented in FIG. 1 for: A) head housing cover and base, B) core casing, C) primary conductor;

(4) FIG. 3 presents a detail “a” from FIG. 1;

(5) FIG. 4 presents a detail “b” from FIG. 1;

(6) FIG. 5 presents a detail “c” from FIG. 1;

(7) FIG. 6 presents a detail “d” from FIG. 1;

(8) FIG. 7 presents a second embodiment of the invention in the form of voltage transformer in a cross-section;

(9) FIG. 8 presents an arrangement of solid insulation material coating for the embodiment presented in FIG. 7 for: D) bottom flange of the column of the voltage transformer, E) bottom external housing, F) core;

(10) FIG. 9 presents a detail “e” from FIG. 7;

(11) FIG. 10 presents a detail “f” from FIG. 7; and

(12) FIG. 11 presents a detail “g” from FIG. 7.

(13) The instrument transformer having a form of a current transformer 1 according to the invention presented on FIGS. 1-6, consists of a head transformer housing 1a having a head housing cover 2 connected with a head housing base 3. The internal surface of the head housing cover 2 and the head housing base 3 is covered with a solid insulation material coating 2a and 3a, respectively. Inside the head transformer housing 1a a core casing 4 is placed. An external surface of the core casing 4 is covered with a solid insulation material coating 4a, the same kind as the coatings 2a and 3a. A primary conductor 5 runs through the housing base 3, and the part of the conductor 5 which is located inside the head housing base 3 is coated with a solid insulation material coating 5a, similar like the coating 4a. In the core casing 4 a core set 6 is located, connected with secondary winding leads 7, running through a current transformer column 8. The core set 6 is embedded in a light filler material 6a, such as e.g. polyurethane foam. The primary conductor 5 is insulated from the head housing base 3 by primary conductor insulators 9, which are sealed in the head housing base 3 by a pair of primary conductor insulator gaskets 10 arranged from to opposite side of the head. In FIG. 3 the only one side of the head is presented. The primary conductor 5 is also sealed from two sides of the housing base 3 by primary conductor gaskets 11. Between the top part of the base 3 and the head housing cover 2 there is a top cover gasket 12 situated. Between the lower part of the base 3 and a top support flange 13a placed on the column 8 there is a head housing base gasket 14. A bottom support flange 13b of the column 8 is placed on a current transformer base 15 and is sealed by a current transformer base gasket 16. To the current transformer base 15 a secondary terminal box 17 is connected to which a secondary winding lead connector 18 is fixed for connecting secondary winding leads 7 with its terminals. The bottom support flange 13b and the current transformer base 15 are connected together with mounting screws 19. To the end of primary conductor 5 projected from the head a pair of primary conductor terminals 20 is coupled. Between the terminals 20 and a top part of the head housing base 3, external to the top part of the head housing base 3 primary conductor nuts 21 are placed to keep the primary conductor 5 in a fixed position. In order to fill a space inside the head transformer housing 1a of the current transformer 1 with insulating gel 22 a filling channel 23 is carried out in the bottom of the housing base 3, which is closed by an inlet plug 24. A filing outlet 25 of the insulating gel 22 is situated on the top of the head housing cover 2 and it is closed by an outlet plug 26. The secondary winding leads 7 are placed in a current transformer lead tube 27, which is placed concentrically within a bushing 28, having field grading layers 29. The current transformer lead tube 27 is sealed by means of the secondary lead plug 30a, through which the secondary leads 7 are passed. Between the top support flange 13a and the bottom support flange 13b an external insulator 30 is placed. The coating 2a, 3a, 4a and 5a is carried out by known technological processes e.g. plasma spraying, flame spraying, powder spraying, or other known method of coating the metal surfaces.

(14) The method of manufacturing process of the current transformer comprises the following steps: a) Preparing the current transformer 1 elements for assembly of the head transformer housing 1a having the head housing cover 2 and the head housing base 3, the core casing 4, the primary conductor 5, next the core set 6 with secondary winding leads 7, the primary conductor insulators 9, the top cover gasket 12, the head housing base gasket 14, the primary conductor gaskets 11, the primary conductor insulator gaskets 10, the primary conductor terminals 20, the primary conductor nuts 21, the filling inlet sealing plug 24 and the filling outlet sealing plug 26; preparation of the current transformer column 8, which comprises the current transformer lead tube 27, column insulating body of current bushing 28 with field-grading layers 29, support flanges top 13a and bottom 13b, external insulator of current transformer 30, secondary lead plug 30a; preparation of the current transformer base 15, the current transformer base gasket 16, the secondary terminal box 17, the secondary winding lead connector 18 and on the end mounting screws 19; b) Coating the internal surface of the head housing cover 2 and the head housing base 3, the external surface of the core casing 4, the external surface of the primary winding conductor 5 with a solid insulation material coating 2a, 3a, 4a, 5a, respectively, by means of e.g. plasma spray, flame spray, powder spray or other known coating process; c) Fitting the core set 6 with the secondary winding leads 7 into the core casing 4 and filling of the remaining void space in the core casing 4 with a light filler material 6a; d) Mounting the column of the current transformer 8 on the current transformer base 15, mounting the head housing base 3 on the current transformer column 8, mounting the core casing 4 on the current transformer lead tube 27, mounting the primary conductor insulators 9 in the head housing base 3 and mounting the primary conductor 5 in either the head housing base 3, or the head housing cover 2; e) Covering the head housing base 3 with the head housing cover 2 and securing it with mounting screws 19, forming the head transformer housing 1a; f) Filling the head transformer housing 1a with the insulating gel 22 by means of any known vacuum filling process; g) Sealing of the filling inlet channel 23 with the filling inlet sealing plug 24 and sealing the filling outlet channel 25 with the filling outlet sealing plug 26.

(15) During step f) the design of the filling inlet channel 23 and the filling outlet channel 25 is prepared in such a way that the length of the channels to their diameters has a ratio between 2:1 and 20:1. Such ratio allows for electrical screening any air voids remaining after filling with the current transformer insulating gel 22 inside the filling inlet channel 23 or the filling outlet channel 25, because the electric field intensity in the channel area is low and cannot give rise to partial discharge during the operation of the current transformer 1.

(16) The instrument transformer having a form of a voltage transformer 31 according to the invention presented on FIGS. 7-11, consists of a bottom external housing 32 and an iron core 33. The internal surface of the bottom external housing 32 and the external surface of the core 33 are covered with a solid insulation material coating 32a and 33a respectively. A primary winding 34 with the layers 35 wound on the primary winding tube 36 and a secondary winding 37 are fitted on the core 33. The layers 35 of the primary winding can be made of paper, synthetic nonwoven or e.g. PET. The layers can be impregnated with epoxy or silicone. A column of the voltage transformer 38 is fixed to the bottom external housing 32 by means of the bottom support flange 39a. The internal surface of the bottom support flange 39a is covered with a high dielectric strength coating 39c. The bottom support flange 39a is fixed to the bottom external housing 32 by means of screws 40 and the connection is sealed with the external housing gasket 41. A HV electrode 42 is fixed to the top support flange 39b by means of screws 40, and it is connected to the primary winding 34 by means of the HV lead 43 and the voltage transformer lead tube 44. The voltage transformer lead tube 44 is placed concentrically within a bushing 45, having field grading layers 46. Between the top support flange 39b and the bottom support flange 39a an external insulator 47 is placed. In order to fill the space inside the base 31a of the voltage transformer 31 with insulation gel 48 a filling channel 49 is carried out in the bottom external housing 32, which is closed by an inlet plug 50. A filing outlet channel 51 of the insulation gel 48 is situated in the bottom support flange 39a and it is closed by an outlet plug 52. The coating 32a, 33a, and 39c is carried out by known technological processes e.g. plasma spraying, flame spraying, powder spraying or other known method of coating the metal surfaces.

(17) The method of manufacturing process of the voltage transformer comprises the following steps: a) Preparing of the voltage transformer 31 elements for assembly of the base 31a of the voltage transformer 31 having the bottom external housing cover 32 the core 33, the primary winding 34 with layers 35, wound on the primary the winding tube 36, the secondary winding 37, the mounting screws 40, the external housing gasket 41, the filling inlet plug 50 and the filling outlet plug 52; preparation of the column 38 of the voltage transformer 31, which comprises the bottom support flange 39a, the top support flange 39b, the HV electrode, the HV lead 43, the lead tube 44, the column insulating bushing 45, the field grading layers 46 the external insulator 47; b) Coating the internal surface of the bottom external housing 32, the external surface of the core 33, and the internal surface of the bottom support flange 39a with a solid insulation material coating 32a, 33a, 39c, respectively, by means of e.g. plasma spray, flame spray, powder spray or other known coating process; c) Fitting the primary winding 34, wound on the primary winding tube 36 and the secondary winding 37 concentrically on the core 33 and fitting the core 33 with the mounted primary winding 34 and secondary winding 37 into the bottom external housing 32; d) Mounting the column 38 of the voltage transformer 31 on the voltage transformer base 31a, and connecting the lead tube 44 with the primary winding 34; e) Covering the column 38 with the HV electrode 42 and connecting the HV electrode 42 with the HV lead 43; f) Filling the base 31a with the insulating gel 48 by means of any known vacuum filling process; g) Sealing the filling inlet channel 49 with the filling inlet plug 50 and sealing the filling outlet channel 51 with the filling outlet sealing plug 52.

(18) The HV combined transformer is manufactured in a manner presented for both HV instrument transformer and a HV voltage transformer.

(19) 1—current transformer

(20) 1a—head transformer housing

(21) 2—head housing cover

(22) 2a—coating of head housing cover

(23) 3—head housing base

(24) 3a—coating of head housing base

(25) 4—core casing

(26) 4a—coating of core casing

(27) 5—primary conductor

(28) 5a—coating of primary conductor

(29) 6—core set

(30) 6a—light filler material

(31) 7—secondary winding leads

(32) 8—current transformer column

(33) 9—primary conductor insulators

(34) 10—primary conductor insulator gaskets

(35) 11—primary conductor gaskets

(36) 12—top cover gasket

(37) 13a—top support flange

(38) 13b—bottom support flange

(39) 14—head housing base gasket

(40) 15—current transformer base

(41) 16—current transformer base gasket

(42) 17—secondary terminal box

(43) 18—secondary winding lead connector

(44) 19—mounting screws

(45) 20—primary conductor terminals

(46) 21—primary conductor nuts

(47) 22—insulating gel for the head transformer housing

(48) 23—filing inlet channel

(49) 24—filling inlet plug

(50) 25—filing outlet channel

(51) 26—filling outlet plug

(52) 27—current transformer lead tube

(53) 28—column insulating bushing

(54) 29—field-grading layers of bushing

(55) 30—external insulator of current transformer

(56) 30a—secondary lead plug

(57) 31—voltage transformer

(58) 31a—base of the voltage transformer

(59) 32—bottom external housing

(60) 32a—coating of external housing

(61) 33—core

(62) 33a—coating of core

(63) 34—primary winding

(64) 35—layers of primary winding

(65) 36—primary winding tube

(66) 37—secondary winding

(67) 38—column of the voltage transformer

(68) 39a—bottom support flange

(69) 39b—top support flange

(70) 39c—coating of bottom support flange

(71) 40—mounting screws

(72) 41—external housing gasket

(73) 42—HV electrode

(74) 43—HV lead

(75) 44—lead tube of the voltage transformer

(76) 45—column insulating bushing

(77) 46—field grading layers of the bushing

(78) 47—external insulator of the voltage transformer

(79) 48—insulating gel of the voltage transformer

(80) 49—filling inlet channel

(81) 50—filling inlet plug

(82) 51—filling outlet channel

(83) 52—filling outlet plug