JP2000069653A - Gas-insulated connecting cable, and manufacture and laying thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce manufacturing cost and to facilitate laying by filling the annular space lying between a core and a casing with an insulating gas, and surrounding the core by a pneumatic chamber, which after being inflated, has a cylindrical shape whose diameter is that of the outer sheath of the cable. SOLUTION: A pneumatic chamber 6 including ties is fitted to a specified position, by covering the core of a cable continuously with a pneumatic chamber developed flatly under the core. Two margins of the chamber are arranged next by bringing their end sections into contact with each other, along an axis 25 which is at the vertical upside of the core of the cable. Pneumatic strips 19 and 20 forming the margins of a top tie are lapped over the margins and caused to adhere to them. Lastly, a cover strip 26 puts covering an assembly produced as a result closes the pneumatic chamber, and this gives airtightness to this region, and strengthens it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the field of gas insulated cables.

[0002]

2. Description of the Related Art Such cables are used to transport power. The general principle of such a cable is
Current state of the art, for example French Patent Document FR2,73
8,946, which describes a gas insulated cable incorporating three metal conductors in a hermetic metal casing. The cables are implemented in the form of elements each about 10 meters in length, which are assembled side-by-side, with about 10 such assembled elements forming a cable "segment". The prior art cable has a dedicated element that can change direction.

[0003] Another prior art document, French patent document FR
2,714,204 comprises a cylindrical steel casing filled with 10 ⁴ hPa or more nitrogen under pressure, describes a single-phase gas-insulated cables, metallic conductor of aluminum or copper-based is closed Axially held inside the steel casing by an insulating cone, the aluminum casing forms a magnetic shield that shields the steel casing from magnetic fields generated by current flowing through the conductor. The steel casing is separated from the aluminum casing by rings of filled polymer or plastic material, each ring being arranged in a groove in each metal collar.

[0004] Prior art gas insulated cables use high pressure cables.
Electric field value E that can withstand gas and gas insulation₁
Therefore, the outer diameter is increased. Such a cable
The outer diameter of the insulation space is a single cable with a voltage U
Has a diameter (2 · U / E) ₁) And when
Edge space is outside diameter (2U / E₁) · Exp (1)
When the minimum.

[0005]

The length of the connection of prior art gas insulated cables is a cost of the cables, especially due to having to deliver such cables to the site in short segments due to the diameter of the cable. It is necessary to interconnect the pipe elements or short lengths of corrugated tubes, which are limited by height and are therefore transported on a drum about 0.4 meters in diameter and about 4 meters in diameter, in their original state.

[0006] In addition, the dielectric strength of the gas insulation is significantly affected by contamination with metal powder and by defects in equipotential surfaces caused by the assembly. As described in French patent document FR 2,719,125, it has been proposed to alleviate the disadvantages by a method for detecting arcs flying on cables.

[0007] It is an object of the present invention to provide a gas insulated cable which is less expensive to manufacture, has a smaller cross section than the prior art cable cross section while providing comparable performance, and is easier to lay. By addressing the shortcomings.

[0008]

To this end, the invention provides a method for transporting a connecting segment in a contracted state whose diameter has been reduced substantially by a factor exp (1) = 2.73, The length of the connecting segments is substantially reduced by reducing the inner diameter of the drum and the unit cross section
(2) relates to an inflatable structure that can be significantly increased by reducing it.

In its most general concept, the present invention comprises a core and an outer sheath, wherein the annular space between the core and the casing is filled with an insulating gas and the core, after its expansion, has a diameter that is equal to the outer sheath of the cable. The present invention provides a gas-insulated cable characterized by being surrounded by a cylindrical pneumatic chamber having a diameter of 1 mm.

[0010] The cable advantageously comprises a flexible tie extending between the conductor core and the inner wall of the pneumatic chamber so as to retain the conductor core in the center of the gas-insulated space after expansion of the pneumatic chamber. .

[0011] The flexible tie is preferably made of a discontinuous piece of woven glass fabric, the edges of which are pre-embedded in narrow side pneumatic strips of the same type as the pneumatic chamber.

[0012] In another variation, the cable comprises a non-hermetic tubular wall formed by wrapping a metal foil around an inflatable structure.

[0013] In another variant, the foil is constituted by a seam joint tube comprising an inflatable structure.

[0014] In certain embodiments, the cable further comprises a conductive cladding disposed along a foil surrounding the inflatable structure.

In one variation, the cable comprises a radially reinforced pneumatic structure.

In an advantageous embodiment, the core of the cable is insulated from each other and covered with a cylindrical assembly of conductor strands, for example, mutually twisted in a cylindrical sector, and a semiconductor protective covering. A phase equipotential surface formed by taping.

In one variant, the sheath is a seam-joined tube surrounded by a casing constituted by a spirally arranged conductor, the sheath being radially defined by the seam-joint tube and the protective casing, and the sheath cladding of the sheath. A channel defined laterally by the side space between the elements of

In another variation, the flexible tie comprises one
It is made of an insulating woven fabric obtained from one or more fiber materials.

The present invention also provides that a pneumatic chamber including a tie is provided by providing a conductor core and a pneumatic chamber, and continuously covering the core with a pneumatic chamber that is prepared and fed out flat under the core. Once in place, the two edges of the chamber are then placed edge-to-edge along an axis that is vertically above the core of the cable, and a pneumatic strip that forms the edge of the top tie A method for producing a gas-insulated cable is provided, characterized in that it is superimposed on the edge and glued thereto, and then a cover strip is placed over the assembly thus prepared.

In a variant, the conductor core is first maintained along the axis, then the cylindrical peripheral bottom of said chamber, in a final angular position simultaneously, and near the side strips. By pressing the pneumatic chamber contracted against from the side,
A contracted pneumatic chamber is placed in contact with the conductor core. A pneumatic chamber forms two buckles of similar length on each side of each of the side strips. Four buckles are folded upward, stacked in pairs, pressed against the conductor core, and then held in this position for transporting the structure. By folding the buckle upward, the folded side of the pneumatic chamber can be prevented from penetrating into the bottom around the cylindrical shape of the chamber. The four folds on the sides of the chamber also prevent the side ties and top ties from being pulled or changing the common fixed angular position of the pneumatic strips and strips that adhere to the chamber. The invention also provides that the contracted pneumatic chamber is permanently held in place with respect to the conductor core by a plastic film surrounding the contracted structure, and this protective film is laid after the cable is formed. A method of laying a gas insulated cable is provided, wherein the gas insulated cable is finally cut when the structure partially expands therebetween.

In another particular implementation, the contracted pneumatic structure that makes up the cable is transported to the laying site by a drum and the structure is unwound. After removing the surrounding ties so that the structure can re-expand, the hoist forms a seam joint around the contracted structure. The contracted structure is placed in its final angular and axial position at the bottom of the seam joint tube, and then the hoist overlies the conductive cladding abutting the seam joint tube and then the protective casing.

In a variation of this embodiment, the surrounding tie wrapping around the contracted structure is replaced by a plastic film that continues to insert the structure while the seam joint tube and conductive cladding are formed, Is then cut under the effect of a partially pressurized cable.

In one variation, the structure is partially expanded before the structure is embedded.

The structure can also form an electrical insulation, the gas-insulated casing and the spacers being provided in place at the factory, thereby preventing them from being approached and the connections being laid. To prevent the risk of contamination occurring during

The inflatable connection structure is characterized in that, after inflation, each unipolar cable is surrounded by a pneumatic chamber having a cylindrical shape and the same diameter as the sheath of the cable.

Inside the gas-insulated space, the tie is installed in place at the factory at the same time as the chamber is provided,
As the chamber is expanded, tension is applied, which holds the conductive core in the center of the gas-insulated space.

[0027] The sheath of each unipolar cable is constituted by a non-hermetic tubular wall formed in situ by winding a metal foil around an inflatable structure unwound from a drum.

For example, the foil constitutes a seam joint including an inflatable structure.

[0030] Around the metal foil, a conductive cladding is placed along the straight cable. This cladding
Reduce the electrical resistance of the sheath. It is surrounded by a structure that helps protect the foil and conductive cladding from corrosion and provides strength to the conductive cladding to withstand the electrical forces generated in the presence of short-circuit current.

The seam joint tube containing the inflatable structure performs several functions.

A) the pneumatic chamber provides reinforcement against being pressurized all around the cylinder during inflation;
Therefore, it can withstand the mechanical force generated by the pressure of the electric insulating gas.

B) Combined with the inflated chamber, constitutes a flexible assembly, which is a path that is assembled with a seam joint tube that is unreeled as the cable is unwound. Suitable to be placed in parallel grooves along.

C) Protecting the pressurized and buried cable against the pushing forces transmitted by backfilling and against local forces generated, for example, by tree roots.

D) The high coefficient of friction holds the pneumatic chamber containing the cable in a predetermined initial cable formation position, thereby first preventing the cable from slipping down, and secondly, the pneumatic chamber. To prevent rotation. With these two movements, there is a risk of changing the centering of the cable core inside the electrically insulating space.

E) Due to the lack of tightness of the seam joint, the chamber can be fitted with the cylindrical shape of the seam joint even if there is a local leakage of the insulating gas which causes only a slight internal pressure of the gas to reverse. Ensure that it is held in contact with the entire perimeter.

F) The presence of heat transfer due to backfilling with dissimilar thermal properties, or the presence of a water pipe placed near the junction to limit the temperature, the temperature is evenly distributed around the sheath. Done.

During the short circuit current, the sheath carries a return current that is only slightly different from the phase current. The electric force generated in the phase conductor tends to center the phase conductor inside the cylindrical volume defined by the sheath. These forces increase with increasing eccentricity of the phase conductor. The short-term nature of such forces, and the mass of the phase conductor, cause these effects, among others, until the core moves to the center position for the first time. The shape of the tie and its strength are adapted to the initial eccentricity, regardless of its orientation. The ties limit the lateral displacement of the phase conductor so as to avoid adversely affecting the dielectric strength of the connection.

A variant of this device consists in omitting the metal reinforcement which serves to form the sheath and replacing the relatively weak pneumatic chamber with a radially reinforced pneumatic structure. Such deformed structures cannot be subjected to momentary shrinkage at the bottom of the groove and can only be used in cable tunnels.

Various forms of ties between the pneumatic chamber and the core of the cable are possible. Similarly, various methods of forming cables surrounded by chambers at the factory are possible. Finally, various types of sheaths can be formed in the field. Advantageously, the flexible tie is manufactured from an insulating woven fabric obtained from one or more fibrous materials. The material is strong enough, does not creep for a long time, is resistant to damage caused by temperature or electrical vibration of the cable, and has low brittleness compatible with the method of forming the connection.

By way of example and for purposes of illustrating the feasibility of the connection, the description will refer to a connection with a particular tie arrangement, a particular method of forming cables and chambers in a factory, and the connection will be laid. It becomes a way to form a specific type of sheath on site.

The invention will be better understood on reading the following description given with reference to the accompanying drawings, in which:

[0042]

FIG. 1 shows a core of a cable 1.
This core comprises a cylindrical assembly 2 of conductor strands, which are insulated from each other, for example K
The two straight segments are twisted together within two contacting cylindrical sectors, the cross section of each sector forming an angle of 2 ¹ / K, and are defined by an arc whose diameter is the diameter of the core of the cable. The core further comprises a phase equipotential surface 3 formed by taping the semiconductor tape 4 covered with a mechanical protective cover 5.

FIG. 2 shows that a low pressure is applied to pressurize the pneumatic chamber 6 against the cylindrical periphery of the sheath formed by the seam joint 7 suitable to withstand the forces due to the internal pressure of the insulating gas. FIG. 7 is a cross-sectional view of a final structure laid in a groove after being placed.

A conductive cladding 8 suitable for conducting a sheath current is arranged around the seam joint pipe 7 and a casing 9
This is to protect the seam joint tube 7 and the conductive cladding 8 from corrosion and to mechanically hold these elements in the presence of a short circuit current.

The core 1 is held at the center of the gas insulating space 10 by a flexible tie 11.

The conductive cladding 8 of the sheath is formed by a spirally arranged conductor. The channel 12 is defined radially by the seam joint 7 and by the protective casing 9 and laterally by the lateral space between the elements of the conductive cladding 8 of the sheath. The channel can maintain the pressure around the seam joint at atmospheric pressure, even if the protective casing 9 is airtight.

For example, the flexible tie 11 may be constituted by a discontinuous piece of glass knitted fabric whose two edges are pre-embedded in a narrow side pneumatic strip of the same type as the pneumatic chamber 6. it can.

An arrangement for these ties and a method of forming a pneumatic chamber containing the ties is proposed as follows.

A) A very long pneumatic strip is formed, the width of which is equal to the circumference of the pneumatic chamber 6.

B) Separately, the side ties 13 have side pneumatic strips 15 and 1 whose edges are narrow over their entire length.
6 is formed by a very long strip of woven glass cloth 14 embedded in it.

C) Separately, the top tie 17 is likewise formed by a very long strip of woven glass 18 whose edges are embedded in narrow pneumatic strips 19 and 20 over its entire length.

D) The side tie 13 and the top tie 17 are laid flat on each other by two axial straight seams 21 and 22 so as to unite the ties.

E) The resulting assembly is laid flat so as to be centered in the pneumatic chamber 6 and the side pneumatic strips 15 and 16 are glued to the inner wall of the pneumatic chamber 6.

F) The resulting assembly is rolled up at the factory to place the pneumatic chamber in place around the core 1 of the cable (for subsequent use).

FIG. 3 shows the construction of a pneumatic chamber 6 including a flexible tie 11, which is stored in a rolled-up state before being mounted in place around the core 1 of the cable.

The pneumatic chamber 6 including the tie is
The cable is attached in place by continuously covering the core of the cable with a pneumatic chamber that unfolds flat below the core. Two edges 23 and 24 of the chamber
Is then the axis 2 located vertically above the core of the cable
Along 5, it is arranged end to end. The pneumatic strips 19 and 20, which form the edges of the top tie,
It overlaps the edges 23 and 24 and is glued to them. Finally, a cover strip 26 resting over the resulting assembly closes the pneumatic chamber and
This gives this area tightness and enhances it.

Subsequently, when the chamber is pressurized and contacts the entire inner periphery of the seam joint tube 7, the top tie constitutes a continuous frame 27 containing the core 1 of the cable. Side tie 1
3 also prevents the stretched core 1 from moving sideways. The center of the side tie 13 is located between the axial seams 21 and 22 but is pressed along the bottom surface of the cable core 1, on both sides of which the seam 21 and the side strip 15
The two sides of the side tie 13, which are located between the seam 22 and between the seam 22 and the side strip 16, respectively, are distributed into two inclined planes forming two side branches of inverted Y.

The gluing of the cover strip 26 takes place in the factory before the cables surrounded by the shrunken chamber are put on the drum, which is merely a gluing that requires airtightness. This is made easier by the ties and the strips, which constitute the discontinuous edges arranged in the axial direction.

FIG. 4 shows the arrangement of the pneumatic chamber 6 in which the top tie 17 is fixed to said chamber, thereby forming the top end 25 of the cradle 27. Free portion of glass woven fabric 17 and pneumatic strips 19 and 2
The connection between zeros is collected at the top end 25 around the cylindrical shape of the pneumatic chamber 6. Pneumatic strips 19 and 20 containing non-projecting and embedded edges of glass woven fabric are arranged in a T-shape on both sides of said top end 25 to cover the outer surface of the pneumatic chamber. Finally, the cover pneumatic strip 26 covers the strips 19 and 20, thereby giving this area a tightness and strengthening it.

The tie forming the base has a diameter D_e= D_i・
diameter D centered on the sheath of exp (1)_iWrap the core
When enclosed, it is in the electrically insulating space and at the top of the
That part of the woven glass fabric suspended from the end 25
Top ties on both sides of the curved center in contact with the core of the bull
11 and 17 are provided. In electrical insulation space
The width of the glass woven fabric is as follows. That is, L = D_i・ [1/2 + arc sin (1 / exp
(1)) + (− 1 + exp (2))^1/2] = 4.48
D_i  The total width of the glass woven fabric is
20 by adding the width of the embedded edge to
It is.

FIG. 5 is a cross-sectional view of a cable surrounded by a contracted chamber and suitable for winding on a drum.

The core of the cable is placed horizontally and rests on the bottom end 36 around the cylinder of the pneumatic chamber. The contracted chamber surrounds the side of the core 1 of the cable. A top tie made of woven glass 17 fixed to the contracted chamber is between the core 1 and the contracted chamber. They are not subjected to mechanical stress. Side tie 13
However, the walls of the pneumatic chamber 6 are also fitted with axial seams 2 so that they do not interfere with the folding of the contracted chamber 6.
Adjacent to the core of the cable along 1 and 22. Thereafter, the extra lengths 28-31 of the contracted pneumatic chamber 6 are all folded upwards along the core 1 of the cable and then the contracted structure 33, which has a substantially cylindrical outer shape, is placed on a predetermined drum on the drum. It is held on the core 1 by a peripheral tie 32 which serves to make it easier to put into position.

The core 1 of the cable before being applied to the drum is
It rests on a single thickness of the contracted pneumatic chamber 6. After being unwound from the drum at the installation site,
By keeping the position of the annulus unchanged,
The eventual expansion of the structure can prevent the core 1 or the pneumatic chamber 6 of the cable from rotating.

FIG. 6 shows a site where the connecting portion is laid in the groove 40 for receiving the portion of the connecting portion of the already laid cable. This connection is made on a path 41 parallel to the groove 40. The drum 42 is brought to the road.

The connection includes a contracted structure 33. The structure is paid out while visually inspecting that the top end 25 around the chamber is correctly elevated. The hoist 43 removes the peripheral tie 32 so that the structure can be re-expanded, and then forms the seam joint pipe 7 around the contracted structure 33. The structure 33 contracted at this time is
It is in its final angular and axial position on the bottom 44 of the seam joint. 4 extra lengths of the contracted chamber 28-
The 31 does not fall under the bottom 44, so they do not cause the structure to rotate on expansion.

The perimeter tie 32 can be comprised of a protective plastic film that breaks when the structure begins to expand.

The winding machine 43 then attaches the conductive cladding 8 which comes into contact with the joint pipe 7, and then attaches the protective casing 9.

The structure 33 is partially inflated before filling it. This partial expansion serves the following purposes:
Ensuring that the structure is in its final position, verifying this position, for example by gamma radiography, and correcting the angular position of the top end 25 of the structure by partially rotating the seam joint. After detecting and repairing any leaks, i.e. after the structure has been filled, the final expansion of the structure 33 takes place.

When the connection is cooled by a water pipe placed against the cable, the depth of the groove has little effect on the heat removal. The depth depends on the diameter of the cable, the maximum allowable pressure and thus the type of electrically insulating gas,
If the pressurized enclosure is accidentally punctured, it can be selected to eliminate any possible danger to the cable.

[Brief description of the drawings]

FIG. 1 is a sectional view of a core of a cable.

FIG. 2 is a sectional view of a cable segment.

FIG. 3 is a cross-sectional view of the assembly constituted by the ties and by the pneumatic chamber before forming the cable.

FIG. 4 is a detailed view of a pneumatic chamber in a tie.

FIG. 5 is a cross-sectional view of a contracted pneumatic chamber surrounding a cable core.

FIG. 6 is a schematic view of a cable laid.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable 2 Assembly 3 Phase equipotential surface 4 Semiconductor tape 5 Mechanical protective cover 6 Pneumatic chamber 7 Joint pipe 8 Conductive cladding 9 Casing 10 Gas insulation space 11, 13, 17, 32 Tie 12 Channel 14, 18 Glass woven cloth 15, 16, 19, 20 Pneumatic strip 21, 22 Seam 23, 24 Edge 25 Axis 26 Cover piece 27 Mount 28, 29, 30, 31 Extra length 33 Structure 36 Bottom end 40 Groove 41 Road 42 Drum 43 Hoisting machine 44 Bottom

Claims (15)

[Claims] 1. A gas insulated cable comprising a core and an outer sheath, wherein an annular space between the core and the casing is filled with an insulating gas, the core having a diameter after expansion that is outside the gas insulated cable. A gas-insulated cable which is surrounded by a cylindrical pneumatic chamber having a diameter of a sheath. 2. A flexible tie extending between the conductor core and the inner wall of the pneumatic chamber to retain the conductor core in the center of the gas-insulated space after expansion of the pneumatic chamber. The gas insulated cable according to claim 1. 3. A flexible tie (11) made of a discontinuous piece of woven glass cloth, the edges of which are pre-embedded in narrow side pneumatic strips of the same type as the pneumatic chamber (6). The gas insulated cable according to claim 2, wherein the cable is provided. 4. The method according to claim 1, comprising a non-hermetic tubular wall formed by winding a metal foil around the inflatable structure. Gas insulated cable. 5. The foil according to claim 4, wherein the foil is constituted by a seam joint including an inflatable structure.
A gas insulated cable according to item 1. 6. The gas insulated cable according to claim 4, further comprising a conductive cladding disposed along a foil surrounding the inflatable structure. 7. The gas insulated cable according to claim 1, further comprising a pneumatic structure reinforced in a radial direction. 8. The core of the cable (1) is covered with a cylindrical assembly (2) of conductor strands which are insulated from each other and are for example twisted together in a cylindrical sector, and a mechanical protective cover (5). A gas insulated cable according to at least one of claims 1 to 7, characterized in that it is constituted by a phase equipotential surface (3) formed by taping of a semiconductor tape (4). 9. A seam joint tube (7) in which a sheath is surrounded by a casing constituted by spirally arranged conductors.
And a joint pipe (7) and a protective casing (9)
9. At least one of the claims 1 to 8, characterized in that it comprises a channel (12) defined radially by and laterally defined by a lateral space between elements of the conductor cladding (8) of the sheath. Gas insulated cable as described. 10. Gas insulated cable according to claim 1, wherein the flexible tie (11) is made of an insulating woven fabric obtained from one or more fibrous materials. 11. A pneumatic chamber, wherein a conductor core and a pneumatic chamber are provided, and a core (1) is continuously provided in a pneumatic chamber (6) which is prepared and fed flat under the core.
, The pneumatic chamber (6) containing the tie (11) is put in place, and then the two edges (23, 24) of said chamber lie vertically above the core of the cable Pneumatic strips (19, 20) arranged edge to edge along the axis (25) and bordering the top tie are superimposed on the edges (23, 24) and glued thereto, and then the cover The method of manufacturing a gas-insulated cable according to claim 1, characterized in that a strip (26) is installed over the assembly thus prepared. 12. Simultaneously maintaining the top of the chamber along the axis first and then the bottom (36) of the cylindrical periphery of the chamber in the final angular position, and of the side strips (15 and 16). By pressing the contracted pneumatic chamber against the conductor core from the side, the contracted pneumatic chamber (6) is placed against the conductor core and the pneumatic chamber is placed on one side strip (15). Form two buckles (28 and 30) of similar length on each side of the other side, and form two other buckles (29 and 31) on both sides of the other side strip (16), with four buckles facing upward 12. The gas barrier of claim 11, wherein the gas barrier is folded into pairs, pressed against a conductor core, and then held in this position for transporting the structure. A method of manufacturing an edge cable. 13. The contracted pneumatic chamber comprises:
Plastic film surrounding the contracted structure (3
According to 2), the protective film is permanently held in place with respect to the conductor core, and this protective film is finally cut when the structure partially expands during the cable laying after the cable formation. The method for laying a gas-insulated cable according to claim 11 or 12, wherein the cable is laid. 14. A contracted pneumatic structure (33) comprising a gas insulated cable is transported to a laying site by a drum (42), the structure is unwound, and the structure can be re-expanded. After removing the surrounding ties (32), the hoisting machine (43) retracts the contracted structure (3).
3) forming the seam joint tube (7) around, the contracted structure (33) being placed in the final angular and axial position at the bottom (44) of the seam joint tube, then the hoist 2. The method as claimed in claim 1, wherein the step (43) covers the conductive cladding (8) in contact with the seam joint pipe (7), and then covers the protective casing (9). 15. The method according to claim 14, wherein the structure is partially expanded before embedding the structure.