WO2013113374A1

WO2013113374A1 - Removable under pressure transportation supports for pure gas wall bushings

Info

Publication number: WO2013113374A1
Application number: PCT/EP2012/051578
Authority: WO
Inventors: Giovanni Testin; Luca CROCCO; Milorad SEHOVAC
Original assignee: Alstom Technology Ltd
Priority date: 2012-01-31
Filing date: 2012-01-31
Publication date: 2013-08-08

Abstract

The present invention concerns a wall bushing made in pure gas technology comprising an axial central conductor (15) and a hollow central flange (2) from the end faces of which axially extend two insulating tubes surrounding the central conductor, each tube being ended by a flange that seals it and supports one end of the central conductor, characterized in that said central flange (2) comprises at least one guiding element for guiding said conductor (15) inside said wall bushing, said at least one guiding element being movable between two positions, a first position in which a first end (110) of said guiding element is maintained in contact with said conductor (15) and a second end of said guiding element is tightly fitted into a hole (121) provided through the central flange, and a second position in which the first end (110) of the guiding element is separated from said conductor (15) so as to seal said hole (121).

Description

REMOVABLE UNDER PRESSURE TRANSPORTATION SUPPORTS FOR PURE GAS WALL BUSHINGS.

DESCRIPTION

TECHNICAL DOMAIN AND PRIOR ART

This invention relates to the domains of power electronics and electric power transmission systems and in particular to wall bushings for High and Ultra High AC or DC Voltage applications.

Figure 1 schematically illustrates the general constitution of a wall bushing.

A wall bushing 1 is used to connect the indoor semiconductor converters or other indoor electrical equipment to outdoor equipment both in AC and DC yards .

A bushing 1 comprises an axial central conductor for leading the current through a wall. The central conductor is made from aluminum or copper. The bushing 1 further comprises a central flange 2 which is fixed to the wall and must therefore be at ground potential GND. A first 3a section and a second 3b section extend axially from the end faces of the central flange and consist of two insulating pipes surrounding the central conductor and provided with silicon rubber sheds at their outer surface. Each section 3a, 3b consists of a glass fiber reinforced epoxy or porcelain tube and it is ended by a suitable flange that seals it and supports one extremity of the central conductor. Moreover, each flange carries a connecting terminal 5 that protrudes outside the section for the electrical connection of the bushing to a high voltage device, i.e. a cable or converters. Both ends of the bushing are generally provided with corona shields 6 surrounding the flanges and the connecting terminals to avoid partial discharges in air.

The section 3a, located within the walls, is called inner section, the other section 3b, located outside the walls, is called outer section.

The bushing 1 keeps the axial conductor electrically isolated from the equipment metallic housing equipment or the building walls when operating at several thousand or even hundreds of thousands of volts. To achieve this purpose, high voltage bushings rely on sophisticated insulation systems able to keep a several kV conductor operating safely at only a few centimeters away from the grounded flange 2.

Conventional insulation systems are composed by dry type and gas type bushings.

The major technology used for HV dry type bushings is RIP (standing for Resin-Impregnated Paper) .

This design involves special paper wrapped around the conductor as well as metallic foils placed at strategic locations within this wrap. To achieve its required high dielectric strength, no air or gas bubbles must be trapped among the successive layers of paper. Therefore, the cylinder of wound paper and foil is thoroughly impregnated with a special resin material. The two major disadvantages of this technology are: the difficulty of construction and the relevant mass of the finished assembly. The main technology used for HV gas type bushings is called pure gas. The main insulation consists of compressed SF6 (sulphur hexafluoride ) gas. The two purposes of the compressed SF6 gas are: to insulate the conductor from ground potential and to improve the cooling of the central conductor. The capability to perform the above mentioned actions is related to the gas density. For operation, the bushing is filled with gas at an operative pressure higher or equal than 4 bars gauge at 20°C. The gas is introduced through a valve located in the central flange 2.

The pure gas technology allows the best performance/weight ratio compared to the dry type one and is hence particularly suited for long sized wall bushings.

However, an important drawback of this technology lies in the complexity of the implementation of the bushing.

Indeed during transport and shipping, the wall bushing is filled with dry nitrogen or SF6 gas at a transport pressure to avoid water or dust to penetrate into the inner volume of the bushing. The transport pressure is lower than the operative pressure to limit the risks involved in moving or lifting high pressurized items and its value is generally comprised between 0.2 and 0.5 bars gauge at 20°C.

In order to transport the bushing to the place where it will be assembled and connected to a power plant, the central conductor has to be maintained by provisional supports, made for example from nylon, in order to prevent it from moving and thus, avoid damaging the sections 3a, 3b. These provisional supports have to be removed before putting the bushing into operation otherwise they would generate critical and dangerous electric effects.

The provisional supports pass through a hole provided on a small flange directly welded on the central flange 2, said hole being sealed by a gas tight suitable cap once the provisional supports are removed.

When the shipment containing the bushing arrives at the place where the bushing has to be fixed and connected to a power plant, a complex procedure is performed in order to make the bushing operative.

In broad terms, this procedure comprises the following steps:

- at first, the bushing must be lifted out and placed on supports that are positioned on the ground. The provisional supports are removed and gas valves and rupture disc units are mounted on the central flange at the small flange or at other adequate slots.

next, a vacuum treatment is performed to remove all nitrogen gas and any particles that are contained inside the bushing. This step requires complex equipment and takes a long time. Moreover during this step, a constant alertness is required to avoid dust and particles to be introduced into the bushing .

the bushing is subsequently filled with SF6 gas at transport pressure and then is lifted and fixed into the wall. only then, the bushing is connected to the power plant and is filled with SF6 at operative pressure, and is ready to be used. The vacuum treatment and the changing of gases are costly and need extreme precautions. In addition, they require complex machinery and transportation systems. Therefore, even if the bushings based on pure gas technology are best suited for many applications, their conception must be improved to avoid such inconvenient.

Thus, the object of the present invention is to find a new structure for a bushing based on pure gas technology that solves the above-mentioned problems.

PRESENTATION OF THE INVENTION

The invention concerns a wall bushing made in pure gas technology comprising an axial central conductor and a hollow central flange from the end faces of which axially extend two insulating tubes surrounding the central conductor, each tube being ended by a flange that seals it and supports one end of the central conductor, characterized in that said central flange comprises at least one guiding element for guiding said conductor inside said wall bushing, said at least one guiding element being movable between two positions, a first position in which a first end of said guiding element is maintained in contact with said conductor and a second end of said guiding element is tightly fitted into a hole provided through the central flange, and a second position in which the first end of the guiding element is separated from said conductor so as to seal said hole.

In a preferred embodiment, at least one guiding element comprises a cylindrical metal rod adapted to fit into the hole provided through the central flange and a plastic end, said plastic end being attached to said metal rod and being in contact with said conductor in said first position, said plastic end being separated from said metal rod and seals said hole in said second position.

Preferably, the extremity of the metal rod where the plastic end can be attached presents a threaded protruding section with a diameter less than the diameter of the metal rod, said plastic end comprising on its inner section a threaded bore such that the plastic end can be screwed into said protruding section of the metal rod.

Advantageously, the plastic end is cylindrical and has along its main part an external diameter equal to the diameter of said metal rod such that it protrudes outside the external section of the central flange when the guiding element is in the second position, the tip of the plastic end which is designed to be in contact with the central conductor having an external diameter greater than the diameter of the metal rod.

The wall bushing made in pure gas technology according to the invention can comprise three guiding elements evenly distributed around the central conductor 15 that they support when they are in the first position.

The invention also concerns a socket type module made in pure gas technology comprising an axial central conductor and a hollow central flange part from one face of which axially extends an insulating tube surrounding the central conductor, said tube being ended by a flange that seals it and supports one end of the central conductor, characterized in that said central flange part comprises at least one guiding element for guiding said conductor inside said module, said at least one guiding element being movable between two positions, a first position in which a first end of said guiding element is maintained in contact with said central conductor and a second end of said guiding element is tightly fitted into a hole provided through the central flange part, and a second position in which the first end of the guiding element is separated from said conductor so as to seal said hole.

Advantageously, at least one guiding element comprises a cylindrical metal rod adapted to fit into the hole provided through the central flange part and a plastic end, said plastic end being attached to said metal rod and being in contact with said central conductor in said first position, said plastic end being separated from said metal rod and seals said hole in said second position.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be better understood after reading the following description of example embodiments given purely for guidance and that are in no way limitative, with reference to the appended figures, wherein :

Figure 1 schematically illustrates the general structure of a prior art wall bushing;

Figure 2 is an exploded view showing the structure of a guiding element according to a preferred embodiment of the invention;

Figure 3 shows a sectional view of the central flange of a wall bushing during a sequence of successive steps that consists in moving the guiding element from the first position to the second position, in a preferred embodiment of the invention ;

Figure 4 is an exploded view of the means that ensure a secure and perfect sealing of the hole provided in the central flange when the guiding element is in the second position, according to a preferred embodiment of the invention;

Figure 5 schematically shows a longitudinal sectional view of the general structure of a socket type module or a plug type module.

Identical, similar or equivalent parts of the different figures are marked with the same numbers so as to facilitate comparisons between the different figures .

The different parts shown in the figures are not necessarily drawn at the same scale, to make the figures more easily understandable. DE TAILED PRESENTATION OF PARTICULAR EMBODIMENTS

The concept behind the invention is to conceive provisional supports that can be removed from the outside of the wall bushing under gas transport pressure level without any need for a vacuum treatment and changing of gases.

Therefore, assembly of a high voltage AC or DC wall bushing made in pure gas technology is greatly simplified since only SF6 gas is used.

As shown in figure 1, a wall bushing 1 made in pure gas technology generally comprises an axial central conductor and a hollow central flange 2 from the end faces of which axially extend two insulating tubes surrounding the central conductor, each tube being ended by a flange that seals it and supports one end of the central conductor keeping it in the center of the insulating tubes. Each flange supports a terminal connection 5 that protrudes outside the module in order to connect the central conductor to AC or DC devices. Indeed, the arrangement is designed for allowing electrical current to pass from the terminal connection 5 through the flange and into the central conductor .

According to the invention, the central flange 2 comprises at least one guiding element for guiding the central conductor inside the wall bushing. A guiding element is movable between two positions, a first position in which a first end of the guiding element is maintained in contact with the central conductor and a second end of the guiding element is tightly fitted into a hole provided through the central flange 2, and a second position in which the first end of the guiding element is separated from said conductor so as to seal said hole.

Therefore, the guiding element acts as a provisional support that can be removed from the outside of the wall bushing under gas transport level.

Each insulating tube is made from an insulating material featuring high mechanical, electrical, thermal and resistant qualities. For example, the insulating tube can be made from a glass fiber reinforced epoxy tube with silicon rubber sheds extruding on its outer surface or made from a traditional porcelain insulator.

A ring shaped shield 6 is preferably mounted at the flanges in order to minimize partial discharges and ionization in air.

The respective connections connecting the insulating tubes into the central flange 2 and the flanges are made from cast or machined aluminum and are fastened with screws and nuts and provided with seals such as O-ring gaskets.

The central flange 2 is made from a conductive material such as aluminum.

The central cylindrical conductor is made from aluminum or copper and axially extends along the wall bushing 1.

Figure 2 shows the structure of a guiding element according to a preferred embodiment of the invention. The guiding element is made from two parts: a metal rod 100 and a soft plastic end 110 at the second end of the guiding element. The plastic end 110 is attached to the metal rod 100 and is maintained in contact with the central conductor 15 when the guiding element is in the first position. However, when the guiding element is in the second position, the plastic end 110 is separated from the metal rod 100 so as to remain inside the hole provided through the central flange. Therefore, in the second position, the metal rod 100 is removed away from the wall bushing 1 and does not interfere with the maneuvers of the bushing.

The tip 112 of the plastic end has a convex shape helping it to fit into a corresponding section of the central conductor 15.

Thus, in the first position, when the bushing wall 1 is filled with SF6 at transport pressure, the central conductor 15 is supported by the at least one guiding element and therefore, the movement of the central conductor 15 is limited that prevents the central conductor 15 from damaging the wall bushing 1 during transport or assembly.

When the wall bushing 1 is fixed on a wall, the at least one guiding element is in the second position in order to seal the hole provided through the central flange 2, that permits the filling of the bushing wall 1 with SF6 gas at an operative pressure which is higher than the transport pressure.

According to the invention, all the operations consisting of moving the guiding element from the first position into the second position, or the other way round are performed from the external side of the central flange 2 thus, avoiding the penetration of particles into the wall bushing 1. Moreover the wall bushing 1 is always filled with SF6 gas, at transport pressure and there is no need for a vacuum treatment.

Preferably, the wall bushing 1 comprises three guiding elements evenly distributed (3 pes displaced 120°) around the central conductor 15 that they support when they are in the first position. More precisely, on a section of the central flange 2, three holes through which pass the guiding elements are evenly distributed.

The extremity 101 of the metal rod 100 where the plastic end 110 can be attached presents a protruding section 102 with a diameter less than the diameter of the metal rod 100. The protruding section 102 is threaded and a corresponding bore 111 is made in the plastic end. The thus created inner section of the plastic end is also threaded such that the plastic end can be screwed into the protruding section 102 of the metal rod.

The plastic end 110 has along its main part, of height h, an external diameter equals to the diameter of the metal rod 100 such that the plastic end protrudes outside the external section of the central flange 2 when the guiding element is in the second position. The tip 112 of the plastic end 100 designed to be in contact with the central conductor 15 has an external diameter greater than that of the metal rod 100.

The invention will be now described in details in relation with figures 3 and 4. Figure 3 shows a sectional view of the central flange 2 of a wall bushing during a sequence of successive steps that consists in moving the guiding element from the first position to the second position, in a preferred embodiment of the invention.

Figure 4 is an exploded enlarged view of the means that ensure a secure and perfect sealing of the hole provided in the central flange 2 when the guiding element is in the second position, according to a preferred embodiment of the invention. Figure 4 is a zoom of the part highlighted by a circle referenced by the letter Z on figure 3.

At the first step a' , the guiding element is in the first position. Indeed, the plastic end 110 is screwed onto the metal rod 100 and is directly in contact with the central conductor 15. The metal rod 100 passes through a hole 121 provided on a small flange 120 directly welded on the central flange 2. The hole 121 is provided simultaneously through the central flange 2 and the small flange 120.

The diameter of the hole 121 provided on the small flange 120 and on the central flange 2 is slightly greater than the diameter of the metal rod 100.

At this step, the wall bushing is considered to be filled with SF6 gas at transport pressure and the metal rod 100 can be safely extracted from the wall bushing.

Step b' represents the extraction of the metal rod 100. The gas tightness on the small flange is ensured by built-in Oring gaskets 122 and therefore, the metal rod 100 can be extracted from the central flange 2 (or the central flange part of the socket type module) with no gas leak.

As represented in step c' , the shape of the plastic end is such that this part can remain blocked inside the small flange 120. Indeed, being of greater diameter than the metal rod 100, the tip 112 of the plastic end 110 stops the extraction of the guiding element. As represented in step c' , the part of the plastic end 110 that has an equal diameter to that of the metal rod 100 remains engaged in the hole 121 provided on the small flange 120 and slightly protrudes outside the central flange 2.

The inner gas transport pressure being of higher level than the outside pressure helps keeping the plastic end 110 blocked into the small flange 120 and protruding outside the surface of the small flange 120. The gas tightness on the small flange is ensured by the above mentioned built-in Oring gaskets 122.

Therefore, the metal rod 100 can be extracted from the central flange 2 with no gas leak.

Step ' shows the separation between the metal rod 100 and the plastic end 110. The removal of the metal rod 100 can be done by a suitable tool that is adapted to unscrew the metal rod 100 from the plastic end 110.

At step e' , the guiding element is in the second position in which the plastic end 110 seals the hole 121 provided on the small metal flange 120. In order to ensure a perfect sealing and to resist to high pressures such as the gas operative pressure level, a locking plate 200 is screwed onto the exterior of the metal flange to better secure the sealing of the hole 121.

A hole 201 is provided on the locking plate 200 and its diameter is approximately equal to the diameter of the inner section of the plastic end 110 such that a suitable blocking bolt 210 can be inserted through this hole 201 and screwed within the plastic end 110. The head 211 of the plastic bolt 210 has a diameter greater than that of the hole 201 and therefore, the plastic end 210 can remain in the hole 121 provided in the metal flange 120 even if there is no sufficient pressure in the wall bushing when the blocking bolt 210 is screwed within the plastic end 100.

Finally, a suitable gas tight metal cap 220 covers the head 211 of the blocking bolt and seals the hole 201 and the wall bushing is fixed to a wall through fastening means provided on the central flange 2.

The gas tight metal cap 220 can be screwed onto the locking plate 200. The latter can be screwed onto the metal flange 120.

Subsequently, the gas filling means and the gas control equipment are installed on adequate slots provided on the central flange, normally on the outer section in order to be easily accessible. Then, the wall bushing 1 can be filled with SF6 at operative pressure and connected to a power plant.

The previous procedure can be easily reversed in order to move the guiding element from the second position to the first position. However, before taking any step, the gas operative pressure level of the SF6 gas has to be lowered to the gas transport pressure level.

It is to be noted that thanks to the present invention, the whole operation of insertion/extraction of the metal rod can be performed from the external side of the central flange thus, avoiding the penetration of particles into the wall bushing. Moreover the wall bushing is always filled with SF6 gas, at transport pressure and there is no need for any vacuum treatment.

The wall bushing made in pure gas technology can be a one part wall bushing (especially in the case of small length wall bushing, i.e. ≤ 15 m) or a wall bushing made up of two modules that are assembled and sealed together. In this latter case, the two modules are designed as a plug type module and a socket type module.

Figure 5 shows the general structure of a module that can be either a plug type module or a socket type module.

Each module 20,30 comprises an insulating tube 3 that is axially extended at a first end thereof by an internal tubular section of a central flange part 2a, 2b arranged at a first end of the module. Each module 20,30 has at its second end 22,32 a flange 4 that seals the module and that supports an extremity of the central conductor 15a, 15b so as to keep it in the center of the insulating tube 3. The flange 4 also supports a terminal connection 5 that protrudes outside the module in order to connect the central conductor 15a, 15b to AC or DC devices. Indeed, the arrangement is designed for allowing electrical current to pass from the terminal connection 5 through the flange 4 and into the central conductor 15a, 15b.

Each insulating 3 tube is made from an insulating material featuring high mechanical, electrical, thermal and resistant qualities. For example, the insulating tube can be made from a glass fiber reinforced epoxy tube with silicon rubber sheds extruding on its outer surface or a traditional porcelain insulator.

The respective connections of the insulating tubes 3 to the central flange part 2a, 2b and the flanges 4 are made from cast or machined aluminum and are fastened with screws and nuts and provided with seals such as O-ring gaskets.

The central flange parts 2a, 2b are made from a conductive material such as aluminum.

The central cylindrical conductors 15a, 15b are made from aluminum or copper and axially extend along the plug type module 20 or the socket type module 30.

The central flange part 2a of the plug type module 20 is designed to be reversibly sealed with the central flange part 2b of the socket type module 30 and the modules are designed such that there is an electrical connection between the central conductor 15a of the plug type module and the central conductor 15b of the socket type module when both modules are sealed. When connected to each other, both central conductors 15a, 15b form a resultant central conductor 15.

When sealed together, the central flange part 2a of the plug type module 20 and the central flange part 2b of the socket type module 30 form the central flange 2 of a wall bushing. Consequently, the present invention described in relation with figure 1 to figure 4 applies for a wall bushing made by the sealing of a plug type module and a socket type module as described above. However, the at least one guiding element is provided on the socket type module side. Thus, according to the invention and in relation with figures 3 and 4, the central flange part 2b of the socket type module 30 comprises at least one guiding element for guiding the central conductor 15b inside the socket type module. The at least one guiding element being movable between two positions, a first position in which a first end of the guiding element is maintained in contact with the central conductor 15b and a second end of the guiding element is tightly fitted into a hole 121 provided through the central flange part 2b, and a second position in which the first end of the guiding element is separated from the central conductor 15b so as to seal said hole.

The guiding element has the same structure as the one described in relation with the figure 2. When the two modules are connected to form a resultant wall bushing, the steps for moving a guiding element from the first position to the second position or vice versa are identical to those described above in relation with figure 3. Moreover, the means that ensure a secure and perfect sealing of the hole provided in the central flange 2 when the guiding element is in the second position are identical to those described in relation with figure 4 except that they are provided on the central flange part 2b.

The conception of a wall bushing as a kit of two modules allows to easily replace a damaged module with a new module of the same type. This presents a double advantage: on the one hand, it is possible to replace a module without having to change the entire wall bushing, and on the other hand, the change requires less labor or specialized equipment as the dimensions of the handled module are reduced and its dismantling can be done directly from the wall. This conception is particularly advantageous for long length wall bushing (sup 20m) .

The two modules can be sealed in a factory and the resultant wall bushing can be transported to the place where it has to be mounted on a wall, being filled during the transport and assembly with SF6 gas at gas transport pressure level. In this case, the at least one guiding element is in the first position and the central conductor 15b is supported by the at least one guiding element and thus any movement of the resultant central conductor 15 is limited that prevents the central conductor 15 from damaging the inner surface of the resultant wall bushing during its transport or assembly.

In a preferred embodiment of the invention, the wall bushing comprises three guiding elements evenly distributed around the central conductor 15b that they support when they are in the first position. More precisely, on the same section of the central flange part 2b of the socket module, three holes through which pass the guiding elements are evenly distributed.

The wall bushing formed by the connection of the two modules can be fixed on a wall through fastening means provided either on the central flange part 2a of the plug type module 20 or on the central flange part 2b of the socket type module 30.

The central flange part 2a of the plug type module 20 comprises fixed supporting means for ensuring mechanical support of the central conductor 15a at the first end 21 of the plug type module (the central conductor being supported by the flange 4 at the second end of each module) . Therefore, when the socket type 30 module is disconnected from the plug type module 20, the central conductor 15a of the plug type module 20 is still supported at one of its ends by the fixed supporting means and the central conductor 15b of the socket type module 30 can be supported at one of its ends by the guiding element according to the invention when that guiding element is in the first position.

Therefore, when a module has to be replaced whereas the wall bushing is mounted on a wall, it is possible to move the at least one guiding element of the socket module from the second position to the first position after having lowered the pressure from operative pressure to transport pressure (for security reasons), before removing the bushing from the wall. In this case, the central conductor 15a, 15b in each module is supported either by the fixed supporting means or by at least one guiding element that prevents it from moving and thus damaging the module.

Claims

1. Wall bushing (1) made in pure gas technology comprising an axial central conductor (15) and a hollow central flange (2) from the end faces of which axially extend two insulating tubes surrounding the central conductor, each tube being ended by a flange that seals it and supports one end of the central conductor, characterized in that said central flange (2) comprises at least one guiding element for guiding said conductor (15) inside said wall bushing, said at least one guiding element being movable between two positions, a first position in which a first end (110) of said guiding element is maintained in contact with said conductor (15) and a second end of said guiding element is tightly fitted into a hole (121) provided through the central flange, and a second position in which the first end of the guiding element is separated from said conductor so as to seal said hole .

2. Wall bushing made in pure gas technology according to claim 1, wherein said at least one guiding element comprises a cylindrical metal rod (100) adapted to fit into the hole (121) provided through the central flange and a plastic end (110), said plastic end being attached to said metal rod and being in contact with said conductor (15) in said first position, said plastic end being separated from said metal rod and seals said hole in said second position.

3. Wall bushing made in pure gas technology according to claim 2, wherein the extremity (101) of the metal rod (100) where the plastic end (110) can be attached presents a threaded protruding section (102) with a diameter less than the diameter of the metal rod (100), said plastic end (110) comprising on its inner section a threaded bore (111) such that the plastic end can be screwed into said protruding section (102) of the metal rod.

4. Wall bushing made in pure gas technology according to claim 2 or 3, wherein the plastic end (110) is cylindrical and has along its main part (h) an external diameter equal to the diameter of said metal rod (100) such that it protrudes outside the external section of the central flange (2) when the guiding element is in the second position, the tip (112) of the plastic end (110) which is designed to be in contact with the central conductor (15) having an external diameter greater than the diameter of the metal rod.

5. Wall bushing made in pure gas technology according to any one of the preceding claims, wherein it comprises three guiding elements evenly distributed around the central conductor 15 that they support when they are in the first position.

6. Socket type module made in pure gas technology comprising an axial central conductor (15b) and a hollow central flange part (2b) from one face of which axially extends an insulating tube (3) surrounding the central conductor, said tube being ended by a flange (4) that seals it and supports one end of the central conductor, characterized in that said central flange part (2b) comprises at least one guiding element for guiding said conductor inside said module, said at least one guiding element being movable between two positions, a first position in which a first end (110) of said guiding element is maintained in contact with said central conductor (15b) and a second end of said guiding element is tightly fitted into a hole (121) provided through the central flange part (2b) , and a second position in which the first end of the guiding element is separated from said conductor so as to seal said hole.

7. Socket type module made in pure gas technology according to claim 6, wherein said at least one guiding element comprises a cylindrical metal rod (100) adapted to fit into the hole (121) provided through the central flange part (2b) and a plastic end (110), said plastic end being attached to said metal rod and being in contact with said central conductor (15b) in said first position, said plastic end being separated from said metal rod and seals said hole in said second position.