FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A modified sealing mechanism for Gas Insulated Switchgear and Gas Insulated Switchgear with modified sealing mechanism, thereof.
APPLICANTS (S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S)
Bhangaonkar Avinash and Ramaswamy Muthuraj; both of Crompton Greaves Limited, High Voltage Product Technology, CG Global R&D Centre, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India; both Indian Nationals.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to the field of mechanical assemblies and switchgear equipment.
Particularly, this invention relates to a current transformer (CT) for Gas Insulated Switchgear (GIS) equipment.
Specifically, this invention relates to a modified sealing mechanism for Gas Insulated Switchgear and Gas Insulated Switchgear with modified sealing mechanism, thereof.
BACKGROUND OF THE INVENTION:
The term 'switchgear', used in association with the electric power system, or grid, refers to the combination of electrical disconnects, earthing-switches and/or circuit breakers used to isolate electrical equipment and networks. Switchgear is used both to de-energize equipment to allow maintenance work to be done and to clear faults.
An effective form of switchgear is gas insulated switchgear (GIS). In a GIS, there is a plurality of electrical components where the conductors and contacts are electrically insulated by pressurized sulfur hexafluoride gas (SF6).
A Gas Insulated Switchgear (GIS) comprises a plurality of electrical components and includes gas as primary insulating medium typically at high voltages.
Electrical isolation is required between the ground plane, on which current transformer cores are mounted, and the flange at one end. For this, typically, there is a gap left between the ground plane and flange at one end. Hence, the cores used in GIS get immersed in the SFg gas which moves freely from inside of the ground plane to the outside (but still within the enclosure). However, the enclosure diameter becomes large which then increases the thickness of the enclosure so as to be able to withstand the burst pressure. This also leads to increased requirement of SFg for the current transformer. Due to the large dimension of the current transformer enclosure, the length of sealing required also increases considerably.
US6014072 discloses a Current Transformer support tube electrically insulated from the bottom closure end plate by means of an insulating ring and is electrically connected to the top closure end plate.

JP2007049102 discloses seals in the inner skin of the flange of the tank, and is equipped with the sealant for air tightness of the tank.
EP1844482 discloses an adhesive insulating layer provided as a support for the annular cores and arrangement of tubular enclosure with CT connected through metallic flanges.
However, none of the above documents discloses a means which would reduce the material requirement for the overall enclosure and the ground plane itself. Thus, there remains a need for a means which would reduce the probability of gas leakage as well as reduce the ground plane and material requirements.
OBJECTS OF THE INVENTION:
An object of the invention is to provide an improved insulating ring for electrical isolation between the ground plane and the flange.
Another object of the invention is to provide an insulating ring having multiple / single overlapping slots in two dimensions to reduce the probability of gas leakage.
Yet another object of the invention is to reduce the material requirement for the current transformer enclosure.
Still another object of the invention is to reduce the length of sealing for the current transformer enclosure.
An additional object of the invention is to reduce the overall cost of the current transformer enclosure.
Yet an additional object of the invention is to provide complete sealing of gas in a gas insulated switchgear equipment.
SUMMARY OF THE INVENTION:
According to the invention, there is provided a modified sealing mechanism for Gas Insulated Switchgear having a ground plane to house conductors in a flanged housing, said mechanism comprises an insulating ring adapted to envelope an operative top end of said ground plane in order to provide electrical isolation between said ground plane and said flange, said insulating ring being juxtaposed in between said ground plane and said flange portion of the housing enveloping said ground plane, characterised in that:

a) said insulating ring further comprising multiple projections located along its inner circumference, said multiple projections adapted to form a locus of dashed points equidistant from the centre to form a dashed circle, said multiple projections incorporating a first set of projections, with respect to a first locus of points, having a first pre-defined height, and further incorporating a second set of projections, with respect to a second locus of points, having a second pre-defined width; and
b) said ground plane further comprising multiple slots located along its outer circumference and along its upper rim, said multiple slots adapted to form a locus of dashed points equidistant from the centre to form a dashed circle, said multiple slots incorporating a first set of slots, with respect to a first locus of points, having a first pre-defined depth, and further incorporating a second set of slots, with respect to a second locus of slots, having a second pre-defined width;
wherein said first set of projections are synchronous in placement, position, and dimensions to said first set of slots such that they fit into each other in a complementary fashion and wherein said second set of projections are synchronous in placement, position, and dimensions to said second set of slots such that they fit into each other in a complementary fashion.
According to the invention, there is provided a Gas Insulated Switchgear having a ground plane to house conductors in a flanged housing with modified sealing mechanism, said mechanism comprises an insulating ring adapted to envelope an operative top end of said ground plane in order to provide electrical isolation between said ground plane and said flange, said insulating ring being juxtaposed in between said ground plane and said flange portion of the housing enveloping said ground plane, characterised in that:
I. said insulating ring further comprising multiple projections located along its inner circumference,
said multiple projections adapted to form a locus of dashed points equidistant from the centre to
form a dashed circle, said multiple projections incorporating a first set of projections, with
respect to a first locus of points, having a first pre-defined height, and further incorporating a
second set of projections, with respect to a second locus of points, having a second pre-defined
width; and
II. said ground plane further comprising multiple slots located along its outer circumference and
along its upper rim, said multiple slots adapted to form a locus of dashed points equidistant
from the centre to form a dashed circle, said multiple slots incorporating a first set of slots, with
respect to a first locus of points, having a first pre-defined depth, and further incorporating a
second set of slots, with respect to a second locus of slots, having a second pre-defined width;

wherein said first set of projections are synchronous in placement, position, and dimensions to said first set of slots such that they fit into each other in a complementary fashion and wherein said second set of projections are synchronous in placement, position, and dimensions to said second set of slots such that they fit into each other in a complementary fashion.
Typically, said first set of projections relate to an operative top layer.
Typically, said second set of projections specifically relate to an operative bottom layer.
Typically, said first set of slots relate to an operative top layer located at an operative top rim of said ground plane.
Typically, said second set of slots relate to an operative bottom layer located at an operative top external circumference of said ground plane.
Typically, said first set of projections (on the insulating ring) having a first pre-defined height are synchronised in positioning and placement with said first set of slots (on the ground plane).
Typically, said first pre-defined height corresponds to said first pre-defined depth.
Typically, said second set of projections (on the insulating ring) having a second pre-defined width are synchronised in positioning and placement with said second set of slots (on the ground plane).
Typically, said second pre-defined width corresponds to said second pre-defined depth.
Preferably, said ring is an epoxy ring.
Typically, said first locus of points of said first set of projections is angularly displaced with respect to said second locus of points of said second set of projections.
Typically, said first locus of points of said first set of slots is angularly displaced with respect to said second locus of points of said second set of slots.
Typically, said each of said projections is spaced apart from a neighbouring projection.
Typically, said each of said projections is joined to a neighbouring projection to form a continuous projection ring.

Typically, said each of said slots is spaced apart from a neighbouring slot.
Typically, said each of said slots is joined to a neighbouring slot to form a continuous slot ring.
Typically, said first set of projections (on the insulating ring) fit into the first set of slots (on the ground plane) as the first pre-defined height (of the projections on the insulating ring) matches the first pre-defined depth (of the slots on the ground plane).
Typically, said second set of projections (on the insulating ring) fit into the second set of slots (on the ground plane) as the second pre-defined width (of the projections on the insulating ring) matches the second pre-defined depth (of the slots on the ground plane).
Preferably, said insulating ring is manufactured by casting it on said ground plane having the said slots pre-machined on it, and said projections on Said insulating ring being created during the casting process in said corresponding slots on said ground, plane.
Preferably, said ground plane and said insulating ring, between an operative upper flange and an operative lower flange is physically covered with fabricated sheet-metal cover.
Preferably, said ground plane and said insulating ring, between an operative upper flange and an operative lower flange is held together by tie-rods.
Preferably, said ground plane and said insulating ring, between an operative upper flange and an operative lower flange is physically covered with a cast aluminum cover.
Preferably, said ground plane and said insulating ring, between an operative upper flange and an operative lower flange is held together by screws between a cast covering said entire assembly between an operative upper flange and an operative lower flange.
Typically, the insulating ring is cast on said ground plane.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a cross sectional view of Gas Insulated Switchgear (GIS) - Current Transformer according to the prior art; and
Figure 2 illustrates a close-up view of Flange Sealing of a ground plane with the flange in an insulated manner.

The invention will now be described in relation to the accompanying drawings, in which:
Figure 3 illustrates a cross sectional view of Gas Insulated Switchgear - Current Transformer with the modified sealing mechanism;
Figure 4 illustrates a close-up view of the modified sealing mechanism along with flange of the Gas Insulated Switchgear - Current Transformer of Figure 3;
Figure 5 illustrates complete view of the insulating ring which is a part of the modified sealing mechanism;
Figure 6 illustrates complete view of the ground plane which is a part of the modified sealing mechanism;
Figure 7 illustrates an isometric complete view of the Current Transformer along with the modified sealing mechanism;
Figure 8 illustrates another isometric complete view of the Current Transformer (cover is made transparent) along with the modified sealing mechanism;
Figure 9 illustrates a sectional view of the Gas Insulated Switchgear - Current Transformer with the modified sealing mechanism (without the top flange);
Figure 10 illustrates a sectional view of the Gas Insulated Switchgear - Current Transformer with the modified sealing mechanism (with the top flange);
Figure 11 illustrates a close-up of the top part of the sectional view of Figure 10;
Figures 12a and 12b illustrate a single impediment zone (depicted by arrows) that the gas may have to overcome in order to escape from the sealing provided by the ground plane and the insulating ring; and
Figures 12c illustrates a dual impediment zone (depicted by arrows) that the gas may have to overcome in order to escape from the sealing provided by the ground plane and the insulating ring.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a cross sectional view of Gas Insulated Switchgear (GIS) - Current Transformer according to the prior art.

Figure 2 illustrates a close-up view of Flange Sealing of a ground plane with the flange in an insulated manner.
There is provided a ground plane (20) on which current transformer cores are mounted and through which conductors are passed. The ground plane, typically, is a cylinder which is electrically isolated from a flange (22) portion at it its operative top end by means of a gap between the ground plane and the flange. Hence, the cores used in GIS get immersed in the SF6 gas which moves freely from inside of the ground plane to the outside (but still within the enclosure).
Due to this, the diameter of the entire enclosure which includes the flange and which houses the ground plane becomes large, as there is a need for a definitive gap between the ground plane and the flange, and the size cannot be reduced in lieu of the warranted gap. Consequently, the thickness of the enclosure has to be increased. The length of the sealing required is also increased considerably. Due to the large dimension of the current transformer enclosure, the length of sealing required also increases considerably.
According to this invention, there is provided a modified sealing mechanism for Gas Insulated Switchgear.
Figure 3 illustrates a cross sectional view of Gas Insulated Switchgear - Current Transformer with the modified sealing mechanism.
Figure 4 illustrates a close-up view of the modified sealing mechanism along with flange of the Gas Insulated Switchgear - Current Transformer of Figure 3.
Figure 5 illustrates complete view of the insulating ring which is a part of the modified sealing mechanism.
Figure 6 illustrates complete view of the ground plane which is a part of the modified sealing mechanism.
Figure 7 illustrates an isometric complete view of the Current Transformer along with the modified sealing mechanism.
Figure 8 illustrates another isometric complete view of the Current Transformer (cover is made transparent) along with the modified sealing mechanism.

Figure 9 illustrates a sectional view of the Gas Insulated Switchgear - Current Transformer with the modified sealing mechanism (without the top flange).
Figure 10 illustrates a sectional view of the Gas Insulated Switchgear - Current Transformer with the modified sealing mechanism (with the top flange).
Figure 11 illustrates a close-up of the top part of the sectional view of Figure 10.
In accordance with an embodiment of this invention, there is provided an insulating ring (24) adapted to envelope the operative top end of the ground plane (20) in order to provide electrical isolation between the ground plane and the flange (22). The insulating ring is juxtaposed in between the ground plane and the flange portion of the housing enveloping the ground plane. Further, the insulating ring is in communication with the ground plane as well as the flange, in that, the inner circumference is enveloped around the ground plane edge and the outer circumference is in communication with the flange portion at its operative inner surface.
In accordance with another embodiment of this invention, the insulating ring has multiple projections (10, 12) located along its inner circumference. These projections form a locus of dashed points equidistant from the centre and form a dashed circle. The dashed points are in relation to the length of each of the projections. There is a first set of projections defined by reference numeral 10. There is a second set of projections defined by reference numeral 12. The first set of projections has a first pre-defined height. The second set of projections has a second pre-defined width. The first set of projections specifically relate to an operative top layer. The second set of projections specifically relate to an operative bottom layer.
In accordance with yet another embodiment of this invention, there are provided multiple slots (14, 16) located along the outer circumference of the ground plane and along the upper rim of the ground plane. These slots form a locus of dashed points equidistant from the centre and form a dashed circle. The dashed points are in relation to the length of each of the slots. There is a first set of slots defined by reference numeral 14. There is a second set of slots defined by reference numeral 16. The first set of slots has a first pre-defined depth. The second set of slots has a second pre-defined depth. The first set of slots specifically relate to an operative top layer. The second set of slots specifically relate to an operative bottom layer.
The first set of projections (on the insulating ring) having a first pre-defined height are synchronised

in positioning and placement with the first set of slots (on the ground plane). Also, the first predefined height corresponds to the first pre-defined depth.
The second set of projections (on the insulating ring) having a second pre-defined width are in synchronised in positioning and placement with the second set of slots (on the ground plane). Also, the second pre-defined width corresponds to the second pre-defined depth.
Therefore, the first set of projections (on the insulating ring) fit into the first set of slots (on the ground plane) as the first pre-defined height (of the projections on the insulating ring) matches the first pre-defined depth (of the slots on the ground plane). Correspondingly, further, the second set of projections (on the insulating ring) fit into the second set of slots (on the ground plane) as the second pre-defined width (of the projections on the insulating ring) matches the second pre-defined depth (of the slots on the ground plane).
The insulating ring is manufactured by casting it on the said ground plane having the slots pre-machined on it. The projections on the insulating ring are created during the casting process in the corresponding slots on the ground plane.
Still further, the locus of points of the first set of projections is angularly displaced with respect to the locus of points of the second set of projections. Similarly, in a complementary fashion, the locus of points of the first set of slots is angularly displaced with respect to the locus of points of the second set of slots.
Each of the projections may be spaced apart from the neighbouring projection. Or the projections may be joined to form a continuous ring.
Each of the slots may be spaced apart from the neighbouring projection. Or the slots may be joined to form a continuous ring.
Figures 12a and 12b illustrate the single impediment zone (depicted by arrows) that the gas may have to overcome in order to escape from the sealing provided by the ground plane and the insulating ring. Reference numeral 12 depicts the one of the projections from the bottom layer which mates with the slots 16 on the side of the ground plane. Reference numeral 10 depicts the one of the projections from the top layer which mates with the slots 14 on the top of the ground plane. Since, the top layer and bottom layer are angularly displaced with respect to each other, at some places or instance, the gas may have a dual impediment zone (as seen in Figure 2c) that the gas may have to

overcome in order to escape from the sealing provided by the ground plane and the insulating ring. Reference numeral 12 depicts the one of the projections from the bottom layer which mates with the slots 16 on the side of the ground plane. Reference numeral 10 depicts the one of the projections from the top layer which mates with the slots 14 on the top of the ground plane.
Hence, an enabling insulation and an enabling sealing is provided.
This enables reduction in the sealing locations and also lengths of sealing are reduced, thus thereby reducing the probability of gas leakage.
The ring can be an epoxy ring.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A modified sealing mechanism for Gas Insulated Switchgear having a ground plane to house
conductors in a flanged housing, said mechanism comprising an insulating ring adapted to
envelope an operative top end of said ground plane in order to provide electrical isolation
between said ground plane and said flange, said insulating ring being juxtaposed in between said
ground plane and said flange portion of the housing enveloping said ground plane, characterised
in that:
a) said insulating ring further comprising multiple projections located along its inner circumference, said multiple projections adapted to form a locus of dashed points equidistant from the centre to form a dashed circle, said multiple projections incorporating a first set of projections, with respect to a first locus of points, having a first pre-defined height, and further incorporating a second set of projections, with respect to a second locus of points, having a second pre-defined width; and
b) said ground plane further comprising multiple slots located along its outer circumference and along its upper rim, said multiple slots adapted to form a locus of dashed points equidistant from the centre to form a dashed circle, said multiple slots incorporating a first set of slots, with respect to a first locus of points, having a first pre-defined depth, and further incorporating a second set of slots, with respect to a second locus of slots, having a second pre-defined width;
wherein said first set of projections are synchronous in placement, position, and dimensions to said first set of slots such that they fit into each other in a complementary fashion and wherein said second set of projections are synchronous in placement, position, and dimensions to said second set of slots such that they fit into each other in a complementary fashion.
2. A modified sealing mechanism as claimed in claim 1 wherein, said first set of projections relate to an operative top layer.
3. A modified sealing mechanism as claimed in claim 1 wherein, said second set of projections specifically relate to an operative bottom layer.
4. A modified sealing mechanism as claimed in claim 1 wherein, said first set of slots relate to an operative top layer located at an operative top rim of said ground plane.

5. A modified sealing mechanism as claimed in claim 1 wherein, said second set of slots relate to an operative bottom layer located at an operative top external circumference of said ground plane.
6. A modified sealing mechanism as claimed in claim 1 wherein, said first set of projections (on the insulating ring) having a first pre-defined height are synchronised in positioning and placement with said first set of slots (on the ground plane).
7. A modified sealing mechanism as claimed in claim 1 wherein, said first pre-defined height corresponds to said first pre-defined depth.
8. A modified sealing mechanism as claimed in claim 1 wherein, said second set of projections (on the insulating ring) having a second pre-defined width are synchronised in positioning and placement with said second set of slots (on the ground plane).
9. A modified sealing mechanism as claimed in claim 1 wherein, said second pre-defined width corresponds to said second pre-defined depth.
10. A modified sealing mechanism as claimed in claim 1 wherein, said ring is an epoxy ring.
11. A modified sealing mechanism as claimed in claim 1 wherein, said first locus of points of said first set of projections is angularly displaced with respect to said second locus of points of said second set of proj ections.
12. A modified sealing mechanism as claimed in claim 1 wherein, said first locus of points of said first set of slots is angularly displaced with respect to said second locus of points of said second set of slots.
13. A modified sealing mechanism as claimed in claim 1 wherein, said each of said projections are spaced apart from a neighbouring projection.
14. A modified sealing mechanism as claimed in claim 1 wherein, said each of said projections are joined to a neighbouring projection to form a continuous projection ring.

15. A modified sealing mechanism as claimed in claim 1 wherein, said each of said slots are spaced apart from a neighbouring slot.
16. A modified sealing mechanism as claimed in claim 1 wherein, said each of said slots are joined to a neighbouring slot to form a continuous slot ring.
17. A modified sealing mechanism as claimed in claim 1 wherein, said first set of projections (on the insulating ring) fit into the first set of slots (on the ground plane) as the first pre-defined height (of the projections on the insulating ring) matches the first pre-defined depth (of the slots on the ground plane).
18. A modified sealing mechanism as claimed in claim 1 wherein, said second set of projections (on the insulating ring) fit into the second set of slots (on the ground plane) as the second predefined width (of the projections on the insulating ring) matches the second pre-defined depth (of the slots on the ground plane).
19. A modified sealing mechanism as claimed in claim 1 wherein, said insulating ring is manufactured by casting it on said ground plane having the said slots pre-machined on it, and said projections on said insulating ring being created during the casting process in said corresponding slots on said ground plane.
20. A modified sealing mechanism as claimed in claim 1 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being physically covered with fabricated sheet-metal cover.
21. A modified sealing mechanism as claimed in claim 1 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being held together by tie-rods.
22. A modified sealing mechanism as claimed in claim 1 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being physically covered with a cast aluminum cover.

23. A modified sealing mechanism as claimed in claim 1 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being held together by screws between a cast covering said entire assembly between an operative upper flange and an operative lower flange.
24. A modified sealing mechanism as claimed in claim 1 wherein, said insulating ring is cast on said ground plane.
25. A Gas Insulated Switchgear having a ground plane to house conductors in a flanged housing with modified sealing mechanism, said mechanism comprising an insulating ring adapted to envelope an operative top end of said ground plane in order to provide electrical isolation between said ground plane and said flange, said insulating ring being juxtaposed in between said ground plane and said flange portion of the housing enveloping said ground plane, characterised in that:
I. said insulating ring further comprising multiple projections located along its inner circumference, said multiple projections adapted to form a locus of dashed points equidistant from the centre to form a dashed circle, said multiple projections incorporating a first set of projections, with respect to a first locus of points, having a first pre-defined height, and further incorporating a second set of projections, with respect to a second locus of points, having a second pre-defined width; and II. said ground plane further comprising multiple slots located along its outer circumference and along its upper rim, said multiple slots adapted to form a locus of dashed points equidistant from the centre to form a dashed circle, said multiple slots incorporating a first set of slots, with respect to a first locus of points, having a first predefined depth, and further incorporating a second set of slots, with respect to a second locus of slots, having a second pre-defined width; wherein said first set of projections are synchronous in placement, position, and dimensions to said first set of slots such that they fit into each other in a complementary fashion and wherein said second set of projections are synchronous in placement, position, and dimensions to said second set of slots such that they fit into each other in a complementary fashion.

26. A Gas Insulated Switchgear as claimed in claim 25 wherein, said first set of projections relate to an operative top layer.
27. A Gas Insulated Switchgear as claimed in claim 25 wherein, said second set of projections specifically relate to an operative bottom layer.
28. A Gas Insulated Switchgear as claimed in claim 25 wherein, said first set of relate to an operative top layer located at an operative top rim of said ground plane.
29. A Gas Insulated Switchgear as claimed in claim 25 wherein, said second set of relate to an operative bottom layer located at an operative top external circumference of said ground plane.
30. A Gas Insulated Switchgear as claimed in claim 25 wherein, said first set of projections (on the insulating ring) having a first pre-defined height are synchronised in positioning and placement with said first set of slots (on the ground plane).
31. A Gas Insulated Switchgear as claimed in claim 25 wherein, said first pre-defined height corresponds to said first pre-defined depth.
32. A Gas Insulated Switchgear as claimed in claim 25 wherein, said second set of projections (on the insulating ring) having a second pre-defined width are synchronised in positioning and placement with said second set of slots (on the ground plane).
33. A Gas Insulated Switchgear as claimed in claim 25 wherein, said second pre-defined width corresponds to said second pre-defined depth.
34. A Gas Insulated Switchgear as claimed in claim 25 wherein, said ring is an epoxy ring.
35. A Gas Insulated Switchgear as claimed in claim 25 wherein, said first locus of points of said first set of projections is angularly displaced with respect to said second locus of points of said second set of projections.

36. A Gas Insulated Switchgear as claimed in claim 25 wherein, said first locus of points of said first set of slots is angularly displaced with respect to said second locus of points of said second set of slots.
37. A Gas Insulated Switchgear as claimed in claim 25 wherein, said each of said projections are spaced apart from a neighbouring projection.
38. A Gas Insulated Switchgear as claimed in claim 25 wherein, said each of said projections are joined to a neighbouring projection to form a continuous projection ring.
39. A Gas Insulated Switchgear as claimed in claim 25 wherein, said each of said slots are spaced apart from a neighbouring slot.
40. A Gas Insulated Switchgear as claimed in claim 25 wherein, said each of said slots are joined to a neighbouring slot to form a continuous slot ring.
41. A Gas Insulated Switchgear as claimed in claim 25 wherein, said first set of projections (on the insulating ring) fit into the first set of slots (on the ground plane) as the first pre-defined height (of the projections on the insulating ring) matches the first pre-defined depth (of the slots on the ground plane).
42. A Gas Insulated Switchgear as claimed in claim 25 wherein, said second set of projections (on the insulating ring) fit into the second set of slots (on the ground plane) as the second predefined width (of the projections on the insulating ring) matches the second pre-defined depth (of the slots on the ground plane).
43. A Gas Insulated Switchgear as claimed in claim 25 wherein, said insulating ring is manufactured by casting it on said ground plane having the said slots pre-machined on it, and said projections on said insulating ring being created during the casting process in said corresponding slots on said ground plane.

44. A Gas Insulated Switchgear as claimed in claim 25 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being physically covered with fabricated sheet-metal cover.
45. A Gas Insulated Switchgear as claimed in claim 25 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being held together by tie-rods.
46. A Gas Insulated Switchgear as claimed in claim 25 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being physically covered with a cast aluminum cover.
47. A Gas Insulated Switchgear as claimed in claim 25 wherein, the entire assembly, comprising said ground plane and said insulating ring, between an operative upper flange and an operative lower flange being held together by screws between a cast covering said entire assembly between an operative upper flange and an operative lower flange.
48. A Gas Insulated Switchgear as claimed in claim 25 wherein, said insulating ring is cast on said ground plane