JP4943957B2 - 3-core batch connection box - Google Patents

Description

  The present invention relates to a three-core batch type connection box for connecting, for example, a three-core OF cable and a three-core CV cable. In particular, the present invention relates to a three-core collective junction box that is lightweight and compact in order to facilitate connection work in a manhole without sufficient space.

  A configuration of an OF cable including an insulating layer in which an insulating oil is impregnated on the outer periphery of a conductor is disclosed in Patent Document 1, for example. Among such OF cables, a three-core OF cable (hereinafter, referred to as an OF cable) having three cable cores with a built-in conductor is widely used for long-distance transportation of high power. Today, the aging parts are often replaced with CV cables (bridged polyethylene cables). In the connection work at that time, it is necessary to take an oil stop measure against the insulating oil filled in the OF cable. Conventionally, for example, as shown in FIG. 12, three conductors 53 and 54 of the OF cable 51 and the CV cable 52 are used. They are connected to each other in a conductive state through conductor connection fittings 56 fitted in oil stop units 55, and the outer periphery of the connection portion of the conductor 53 of the OF cable 51 and the conductor connection fitting 56 is separated by a separate shielding cylinder 58. I was trying to cover it. The oil stop unit 55 is formed of a synthetic resin material in a pointed cylindrical shape, and is held in close contact with the three holes of the metal joint flange 60 erected in the main body cover 59. An oil stop was taken.

In the connection work, the metal sheath 57 of the OF cable 51 is cut and removed by a predetermined length, and the oil passage 62 opened in the semi-stop device 61 is opened by the semi-stop device 61 fitted on the cut portion of the metal sheath 57. Blocked. The semi-stop device 61 is connected to a semi-stopper valve 64 provided on the OF side case 63 by a communication pipe 62. With the configuration as described above, double oil stop measures are taken by the semi-stop device 61 and the oil stop unit 55 against the insulating oil flowing through the oil passage 62 of the OF cable 51, and the three conductors of the OF cable 51 are provided. 53 and the three conductors 54 of the CV cable 52 are connected to each other through the conductor fitting 56. After such connection work is completed, the OF side case 63 is filled with insulating oil, and the power supply is ready for use.
JP 2001-93352 A

  By the way, the connection work as described above is performed in a manhole (not shown) dedicated to the OF cable. In the conventional connection structure shown in FIG. 12, since the length L1 is relatively long, good workability cannot be obtained in the manhole. Therefore, manhole expansion work was sometimes forced. For this reason, there has been a demand for downsizing of the entire connection structure (particularly the length in the axial direction). Further, since the oil stopper unit 55 and the shielding cylinder 58 are provided in each of the three connecting portions, the number of parts is large and the connecting work is troublesome. The metal joint flange 60 that holds the three oil stop units 55 in a close-fitted state is heavy and expensive. For this reason, in order to facilitate the connection work and to reduce the raw material cost, reduction in the number of parts and weight reduction have been demanded. Such a problem of the connection structure is a problem common not only to the connection of different types of cables such as the OF cable and the CV cable, but also to the case of the OF cables.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a three-core batch type connection box that is particularly compact in the length direction, reduced in the number of parts, and reduced in weight.

The three-core batch type connection box of the present invention is a three-core batch type connection box for connecting three-core cables having three cable cores having conductors, and at least one of the three-core cables is OF. The cable is provided with an oil stop function between the OF side case and the OF side case that covers at least the cable connection portion on the OF cable side in an oil-tight state, and the three conductors facing each other are insulated. And a three-core collective insulation connection unit for maintaining connection in a conductive state, and the three-core collective insulation connection unit is disposed upright in a direction perpendicular to the conductor connection direction, and is connected to the OF-side case. A flange portion connected in an oil-tight manner, three bulging portions formed to project from the flange portion toward the conductor connection direction on the OF cable side, and the entire conductor connection portion to which the three conductors are connected Through the insulation layer In the three-core collective junction box having a shielding cylinder to cover, the peripheral edge of the flange portion of the three-core collective insulation connection unit is connected to the connection portion formed in the ring shape of the OF side case. A connection edge is formed, and inside the connection edge is formed a disk-shaped latching step for fitting the base of the shielding tube, and each of the surfaces of the latching step is tapered. The three bulging portions formed in a cylindrical shape are erected, and the concave R portion formed between the connecting edge portion of the flange portion and the latching step portion is part of the periphery of the flange portion. It is characterized in that the curvature is set to be small by biting inward from the surface .

  According to such a configuration, the oil stop measures in the OF side case are applied by the three-core collective insulation connection unit, and the conductors of the three cable cores facing each other to be connected are collectively in an insulated state. Can be connected. This eliminates the need for a conventional expensive and heavy metal joint flange, reduces the number of parts, reduces member costs, and facilitates construction work on site. Moreover, since the whole three conductor connection parts are connected collectively, the space | interval of the radial direction of each conductor connection part can be shortened. This reduces the distance from the cable core branch point to the three-core batch insulated connection unit within the allowable limit of the bending angle of each cable core drawn from the branch point. The axial length of the junction box) can be shortened.

  The three-core collective insulation connection unit is disposed upright in a direction perpendicular to the conductor connection direction, and is connected to the OF side case in an oil-tight manner, and the flange portion is connected to the OF cable side. Three bulging portions that protrude in the conductor connecting direction, and each bulging portion is disposed on the concentric circle at equal intervals and has through holes, and the conductors are arranged in the through holes. You may make it incorporate the conductor connection means for connecting. If it does in this way, the 3 core collective insulation connection unit which consists of three bulging parts which incorporated the flange part and the conductor connection means can be formed by integral molding of synthetic resin materials, such as an epoxy resin, for example.

  You may provide the shielding cylinder which covers the whole conductor connection part to which three conductors are connected through an insulating layer. If it does in this way, since the whole three conductor connection part is collectively covered with a shielding cylinder, the space | interval of the radial direction of each conductor connection part can be shortened. As a result, the entire conductor connecting portion can be made compact in the radial direction, and the distance between the cable cores at the conductor connecting portion can be reduced, so that the axial length of the three-core batch type connection box can be made compact. And since the entire three conductor connection portions are collectively covered with a shielding cylinder, the number of parts can be reduced as compared with the conventional case where the conductor connection is covered with an individual shielding cylinder, and the member cost can be reduced, and the covering work Is also simplified.

  A connection edge to be connected to the ring-shaped connection portion of the OF case is formed on the periphery of the flange portion of the three-core collective insulation connection unit, and the shielding is provided inside the connection edge. A disc-shaped latching step for fitting the base of the tube is formed, and the three bulging portions each formed in a tapered cylindrical shape are erected on the surface of the latching step, A part of the concave R portion formed between the connection edge portion of the flange portion and the latching step portion is bitten inward from the peripheral surface of the flange portion, and the curvature of the concave R portion is set to be small. Also good. In this way, if a part of the concave R portion is configured to bite into the peripheral surface of the flange portion, and a conductive paint is applied to the concave R portion to form an earth line, the three-core collective insulation connection unit is large. The curvature of the concave R portion should be set so small that local concentration of electrical stress that induces dielectric breakdown does not occur between the connection edge of the flange portion and the latching step portion even under the influence of electric field stress. Can do. Thereby, the outer diameter of the flange part of a 3 core collective insulation connection unit can be made small.

  The rising portion of the bulging portion at the portion where the base outer periphery of the bulging portion is separated from the outer periphery of the latching step portion of the flange portion includes the rising portion of the bulging portion and the surface of the hooking step portion. Further, it may be made continuous through an inclined surface that is gentle enough to avoid dielectric breakdown due to local concentration of electric field stress. In this way, even if the three-core collective insulation connection unit is affected by electric field stress, an electrical stress that induces dielectric breakdown between the rising portion of the bulging portion and the surface of the latching step portion. Local concentration is less likely to occur.

  The three-core collective insulation connection unit may be formed by integral molding of epoxy resin. Epoxy resin has good electrical insulation characteristics and moldability and is excellent in oil resistance, so that a three-core collective insulation connection unit with good performance quality and durability can be formed at low cost.

  The shielding cylinder may be formed of a half-cracked smooth metal plate member that can be retained in a cylindrical shape. In order to ensure high dielectric strength with insulating oil, high smoothness is required for the inner surface of the shielding cylinder. However, since the conventional shielding cylinder made of a copper material is joined by silver brazing, the smoothness of the inner surface cannot be sufficiently ensured. This is also the reason why it is difficult to form a three-core shielding cylinder. Therefore, in the present invention, a brass plate member that can easily obtain high smoothness of the surface is formed in a half-crack shape, and this can be held in a cylindrical shape without joining such as silver brazing. By comprising, the high smoothness of the inner surface can be ensured. By covering the entire conductor connecting portion with such a shielding cylinder, electrical stress (electric field stress) is applied to the central part of the three cores up to about 36% of the conventional type in which the shielding cores are provided for the three cores individually. Can be reduced. As a result, it is possible to reduce electrical troubles such as stress failure around the center, such as breakage of insulating paper and occurrence of stress breakdown due to the presence of foreign matter. Further, it is possible to eliminate the work in the central portion where the space is narrow and the workability is not good.

  In order to retain the plate member in a cylindrical shape, the latch member that latches the latched side portions formed on the edge of the plate member is located at an intermediate portion between two adjacent bulging portions. You may make it arrange | position along. When three cable cores are connected together by the three-core collective insulation connection unit, the bulging portions containing the respective conductor connection portions are arranged at equal intervals with a phase interval of 120 °. In that case, the strength of the electric field stress (layering stress) acting on the shielding cylinder is the strongest at the outermost part of each bulging part, and the intermediate phase part between the adjacent bulging parts is the lowest. Therefore, if both the latching side portions are latched by the latching member along the intermediate phase portion, both the latching side portions and the latching member are less affected by the electric field stress. Therefore, a stable latching state can be secured. In this way, the opposite edges of the half-cracked plate member are bent outward to form the hooked side portions, and the hooking member is slid in the axial direction with respect to both the hooked side portions. In the configuration in which both the sides to be latched are engaged, soldering, brazing, or the like is unnecessary, and therefore, high smoothness can be obtained on the inner surface, so that high dielectric strength can be ensured. Moreover, the manufacture is easy and can be obtained at low cost, and the construction work on site is also easy.

  The other of the three-core cables may be a three-core CV cable. As described above, since the oil stop measures can be taken in the OF side case by the three-core collective insulation connection unit, after the connection work between the OF cables is completed, the OF side case is evacuated and then insulated. If the conductor connection part is insulated by filling with oil, it is ready for use.

  The three-core collective junction box of the present invention collectively connects the conductors of the three cable cores facing each other to be connected by applying an oil stop in the OF case by the three-core collective insulation connection unit. Therefore, the conventional expensive and heavy metal splicing flange becomes unnecessary, and the number of parts can be reduced. In addition, since the entire three conductor connection portions are connected together, the distance between the conductor connection portions in the radial direction can be reduced, so that the length of the three-core batch type connection box can be shortened and narrow. Construction work in the manhole is easy.

Hereinafter, the three-core collective junction box according to the embodiment of the present invention will be described.
FIG. 1 is a cross-sectional view of a three-core collective junction box formed in a cylindrical shape. As shown in the figure, inside this three-core collective junction box, three opposing conductors 3a of a three-core OF cable (hereinafter referred to as OF cable) 1 and a three-core CV cable (hereinafter referred to as CV cable) 2 are opposed. , 4a are connected together in a conductive state by the three-core collective insulation connection unit 5, and the entire conductor connection portion 6 to which the three conductors 3a, 4a are connected is formed by a single shielding cylinder 7. Covered. The three-core collective insulation connection unit 5 has an oil stop function and is provided with a disc-shaped flange portion 8 erected in a direction orthogonal to the conductor connection direction, and the OF cable 1 from the flange portion 8. Three bulging portions 9A formed in a tapered cylindrical shape protruding toward the side, and a protruding portion 9B protruding toward the CV cable 2 corresponding to the bulging portion 9A, for example, epoxy It is formed by integral molding of resin, and a conductive paint is baked on its surface in order to maintain insulation.

The flange portion 8 is sandwiched between an OF side case 10 that covers the cable connection portion including the conductor connection portion 6 on the OF cable 1 side in an oil-tight state and a CV side case 30 that covers the cable connection portion of the CV cable 2. Standing up. As shown in FIG. 2, each bulging portion 9 </ b> A that protrudes toward the OF cable 1 side is arranged at equal intervals (120 °) on a concentric circle on one side (front side) of the flange portion 8. conductors 3a to the through hole, is integrally molded in a state in which a built-in 11 (conductor connecting means of the present invention) conductor fittings in order to connect 4a together. On the periphery of the flange portion 8, a connection edge portion 8a connected to a connection ring 10e formed at a connection end of the OF side case 10 by bolt fastening is formed. Inside the connection edge portion 8a, a shielding cylinder is formed. A disc-shaped latching step portion 8b for fitting the base portion 7 is formed. Three bulging portions 9A are erected in the latching step portion 8b. On the back side of the flange portion 8, a protruding portion 9B is formed at a position corresponding to the bulging portion 9A.

  A concave R portion r is formed between the connecting edge portion 8a on the surface side of the flange portion 8 and the latching step portion 8b, for example, as shown in FIGS. A part of r is bitten inward from the peripheral surface of the flange portion 8, the curvature of the concave R portion r is set small, and a conductive paint is applied to the portion to form an earth line. That is, when the concave R portion is formed between the connection edge portion 8a of the flange portion 8 and the latching step portion 8b without causing a portion of the concave R portion r to enter the inner side of the peripheral surface of the flange portion 8, FIG. As indicated by the alternate long and short dash line in FIG. 3 (b), the curvature is increased and the electrical stress is likely to go outside. 3A is a cross-sectional view taken along the line III-III in FIG. Moreover, although illustration is omitted, if a curvature equivalent to the case where the concave portion R is ripped without biting inward from the peripheral surface of the flange portion 8 is set, Not only does the diameter increase, but the position of the bulging portion 9A extends to the left in the axial direction, so the axial length of the three-core collective insulation connection unit 5 increases, which hinders downsizing. A similar concave R portion s is also formed between the connection edge portion 8c on the back surface side of the flange portion 8 and the disk-like stepped portion 8d on which the protruding portion 9B is erected (FIG. 3 (c). )reference). In this way, by forming a part of the concave R portions r, s formed on the front and back surfaces of the flange portion 8 into the front and back surfaces of the peripheral edge of the flange portion 8, the curvature of the concave R portions r, s is configured. Can be set small, and the overall length of the three-core collective insulation connection unit 5 can be shortened. Even if the three-core collective insulation connection unit 5 is affected by a large electric field stress due to lightning impulse or the like, a local electric stress is generated between the peripheral edge of the flange portion 8 and the bulging portion 9A and the protruding portion 9B. The outer diameter of the flange portion 8 can be shortened to such an extent that dielectric breakdown due to concentration does not occur. By providing such a three-core collective insulation connection unit 5, the unit length (D shown in FIGS. 7A and 7B) could be reduced by about 37.8% (434 mm → 270 mm). .

  And in the site | part which the base outer periphery of the bulging part 9A separates from the outer periphery of the latching step part 8b of the flange part 8, as shown to Fig.4 (a) (b), the rising part of the bulging part 9A, The surface of the latching step portion 8b is made continuous through an inclined surface that is gentle enough to avoid dielectric breakdown due to local concentration of electric field stress. A straight line drawn in the radial direction at an angle of 10 °, 20 °, 30 °, 40 °, and 60 ° from the center of the three cores of the three-core collective insulation connection unit 5 has three bulging portions 9A erected. The cross section of the cross section cut in the axial direction of the conductor is drawn and enlarged by a line connecting the intersection intersecting with the outer periphery of the stop portion 8b and the center (center of the conductor) of the bulging portion 9A at the top of the drawing. (FIG. 4A shows cross sections corresponding to 10 °, 30 ° and 60 °, and FIG. 4B shows cross sections corresponding to 20 ° and 40 °). In each cross section, the concave R portion is illustrated by a virtual line. For example, in a three-core collective junction box for connecting a 77-kV three-core cable, a plurality of curved surfaces having different curvatures may be continuously formed on the inclined surface, but the curvature is set so as not to cause concentration of electrical stress. It is preferable that the curved surface is set small. With such a configuration, even if the three-core collective insulation connection unit 5 is affected by a large electric field stress due to lightning impulse or the like, local electrical stress that induces dielectric breakdown around the rising portion of the bulging portion 9A Concentration is less likely to occur. Note that the [lightning impulse withstand voltage test] performed when determining such a shape will be described later.

  The shielding cylinder 7 includes a half-cracked smooth brass plate member 7a that can be held in a cylindrical shape. For example, as shown in FIGS. 5 (a) and 5 (b), the peripheral surface of the plate member 7a includes: Three ring-shaped reinforcing plates 7b are attached, and opposite half-cracked edges are formed with hooked side portions 7c and 7c that are folded back to the outer sides. The latching member 13 having latching sides on both sides latching on the portions 7c and 7c slides in the cylinder axis direction, so that both the latched sides 7c and 7c are latched and detachable. . Therefore, at the site, after the base portion of the plate member 7a is fitted on the latching step portion 8b of the flange portion 8, both the latched side portions 7c and 7c are brought close to each other, and both the latched side portions 7c are placed. , 7c may be slid and latched. In that case, it is preferable to arrange | position the latching member 13 along the intermediate | middle (60 degree) site | part between the two adjacent bulging parts 9 and 9 (refer FIG.11 (b)). In such an intermediate portion, as will be described later, the influence of the electric field stress received from the conductor connecting portion 6 is the least, and a stable latching state by the latching member 13 can be obtained. In addition, the space | interval d between both the latching edge parts 12 and 12 can be set to about 3.0 mm-5.0 mm, for example. Further, the latch member 13 may be divided into, for example, three to four equal parts in consideration of workability. By covering the entire conductor connection portion 6 with such a shielding cylinder 7, the electrical stress (electric field) is reduced to about 64% in the central part of the three cores compared to the conventional configuration in which the shielding cores are provided for the three cores individually. Stress) can be reduced. As a result, it is possible to reduce electrical troubles such as stress failure around the center, such as breakage of insulating paper and occurrence of stress breakdown due to the presence of foreign matter. Further, since the shielding cylinder 7 is made single, the number of parts can be reduced, and the mounting work is facilitated.

  As described above, in the three-core collective junction box according to the present embodiment, the oil-stopping is provided in the OF side case 10 by the three-core collective insulated connection unit 5 that connects and holds the opposing conductors 3 and 4 in a conductive state. By taking measures, the conductors 3a and 4a of the three cable cores 3 and 4 facing each other can be connected to each other in a conductive state, so that a conventional heavy and expensive metal joint flange is unnecessary. Thus, the number of parts can be reduced, and the member cost can be reduced. Moreover, since the whole three conductor connection parts 6 are collectively covered with the single shielding cylinder 7, the radial interval between the respective conductor connection parts 6 is reduced as compared with the conventional case in which the three shielding cylinders are individually provided. It is possible to reduce the size of the entire conductor connection portion 6 in the radial direction in the three-core batch connection box. Since the bending angle of the cable core 3 has an allowable limit, the distance from the branch point 14 to the three-core collective insulation connection unit 5 increases as the distance between the cable cores 3 and 3 at the conductor connection portion 6 increases. Become. In the present embodiment, as described above, the distance between the cable cores 3 and 3 in the conductor connection portion 6 can be reduced, so that the branch point 14 of the cable core 3 reaches the three-core collective insulation connection unit 5. The distance between them (B shown in FIGS. 7A and 7B) could be shortened by about 21.3% (445 mm → 350 mm) as compared with the conventional oil stop unit.

  The other structure and the like will be described in more detail (see FIG. 1). At the connection end of the OF cable 1, the metal sheath 15 is cut and removed by a predetermined length, and the lead is placed on the outer periphery of the cut portion of the metal sheath 15 (spacer seat). ), And the semi-stop device 16 is fitted to the seat lead work through packing and joined by soldering or the like. In the semi-stop device 16, the three cable cores 3a are branched, and the oil passage 17 opened in the semi-stop device 16 has three branch ports for branching and discharging each cable core 3a. It is closed by a packing provided on 16a. The semi-stop device 16 is connected to a semi-stopper valve 19 provided in the OF side case 10 by a communication pipe 18. Accordingly, the oil passage 17 opened in the semi-stop device 16 is closed by the semi-stopper valve 19 so as to be freely opened and closed. The three branched cable cores 3 are expanded at a predetermined interval and are inserted into three holes (not shown) formed in the core wire holding bracket 20 erected in the OF side case 10. Retained. The interval between the hole portions, that is, the interval between the cable cores 3 can be shortened as compared with the conventional case in which the shielding cylinders are individually provided. Accordingly, the three cable cores 3 drawn out from the branch point 14 in the semi-stop device 16 may be bent slightly until reaching the core wire holding fitting 20, and between the branch point 14 and the core wire holding fitting 20. This distance can be shorter than the conventional distance as described above.

  The insulating layer 3b at the tip of the cable core 3 drawn out from the branch point 14 is stripped to expose the tip of the conductor 3, and the tip of the conductor 3 is connected to the three-core collective insulation connection unit 5 via the connection sleeve 21. Is connected to one end (left side in the figure) of the conductor connection fitting 11 protruding from the bulging portion 9. That is, both ends of the connection sleeve 21 are caulked and fixed to the tip of the conductor 3 and one end of the conductor connecting metal 11 by caulking tools. After the insulating oil-impregnated paper 22 is wound around the tip of the cable core 3 sandwiching the connection sleeve 11 and the outer periphery of most of the bulging portion 9A, the metal bell mouth 23 erected in the shielding cylinder 7 Three cable cores 3 are fixedly supported.

  On the other hand, a conductor connection pipe 25 is embedded in a recess formed in the other end (right side in the figure) of the conductor connection fitting 11, and the conductor connection pipe 25 extends from the tip of the cable core 4 of the CV cable 2. The exposed end of the conductor 4a is inserted in a pressed state. That is, a pre-mold insulator (stress cone) 28 is fixed to the end of the cable core 4 in an externally fitted state, and the tapered rear portion of the pre-mold insulator 28 has a mortar-shaped pressing. Via the member 27, the spring 29 of the metal fitting 26 is biased toward the distal end of the cable core 4, and the front half of the pre-molded insulator 28 is pressed against the opening of each protrusion 9 </ b> B of the three-core insulating connection unit 5. Inserted into the state. Although not shown in detail, the pressing bracket 26 is configured to urge the pressing member 27 toward the distal end of the cable core 4 by eight springs 29 guided by eight guide rods. Each of the cable cores 4 is fitted with a respective one of the metal fittings 26 so as to be prevented from moving in the axial direction. With such a configuration, the conductor 3a of the OF cable 1 and the conductor 4a of the CV cable 2 are connected in a close conductive state.

  The OF side case 10 that covers the connection portion of the OF cable 1 (see FIG. 1) is formed in a double structure in which the copper tube 10b is integrated in the anticorrosion cover 10a, and the base 10A formed in the cylindrical shape, The tip portion 10B formed in a sharp tapered shape is integrated with the connection portion 10C. The base portion 10 </ b> A is joined to a CV side case (three-corrosion protection cover) 30 that covers the connection portion of the three-core CV cable 2 in the flange portion 8 of the three-core collective insulation connection unit 5. The OF side case 10 and the CV side case 30 constitute a main body case 40 of a three-core batch type connection box that covers the entire connection portion of both cables 1 and 2. More specifically, in the base portion 10A of the OF side case 10, the connection ring 10e integrated with the base portion of the copper tube 10b is connected to the flange portion 8 of the three-core collective insulation connection unit 5 by bolt fastening via the O-ring. It is integrated on the surface side, and the gap between the anticorrosion cover 10a, the copper tube 10b and the flange portion 8 is filled with a waterproofing compound to form a watertight structure. Further, connectors 37 and 38 for enabling supply and discharge of insulating oil into and from the OF side case 10 are attached to the top and bottom of the base portion 10A, and a ground terminal 39 is attached to the tip portion 10B. .

  On the other hand, in the CV-side case 30 that covers the connection portion of the CV cable 2, three pressing metal fittings 26 respectively fitted to the three cable cores 4 covered with the metal sheath of the CV cable 2 are provided in the conductor connecting direction. A CV-side main body case 32 for supporting the position in a fixed state is provided in a standing state. As shown in FIG. 6, the CV-side body case 32 is connected to a connection ring 30 e via a ring-shaped spacer 33, and the connection ring 30 e is the back surface of the flange portion 8 of the three-core collective insulation connection unit 5. It is integrated with the side connection edge 8a by bolt fastening via an O-ring. On one side (right side in the figure) of the CV-side main body case 32, the base portion of the press fitting 26 is fixed by bolt fastening. The edge (right side in the figure) of the CV-side case 30 is reduced in diameter so as to wrap around the outer peripheral edge of the press fitting 26, and the three cable cores 4 are introduced into the reduced diameter end. A terminal member 35 having three branch ports 35a is connected. With such a configuration, the pre-mold insulator 28 is urged to the left in the figure by the spring 29 of the pressing metal 26 via the pressing member 27, and the conductor 4 a of the CV cable 2 is connected to the OF cable 1. The conductor 3a can be connected in a tight conduction state.

  By compactly storing such a metal fitting 26 in the CV-side case 30, the left and right cable cores 3 and 4 can be connected to each other in the butted state, and the lengths of the portions (FIGS. 7A and 7B). E) shown in FIG. 4) can be shortened by about 29% (356 mm → 254 mm). To summarize the achievement of downsizing in the length direction of the three-core batch type connection box according to the present embodiment, including shortening of the length A (metal end) shown in FIGS. 7 (a) and 7 (b). The total length (total length) of each length B (OF branching portion), C (OF insulating portion), D (3-core batch insulation connecting unit) and E (CV copper tube portion) is the conventional total length L1 ( 2100 mm) in this embodiment could be shortened to L2 (1580 mm). In other words, a reduction of about 25% could be realized. The outer diameter was the same as before.

[Lightning impulse pressure resistance test]
When designing a three-core batch type connection box having the three-core batch insulation connection unit (epoxy resin unit) 5 and the single shielding cylinder 7 as described above, a conventional three-dimensional model (for 77 kV three-core OF) is used. A lightning impulse withstand voltage test was conducted as a test piece, and by pursuing the problems, improvements were made to find a structure capable of ensuring sufficient dielectric strength. The test will be described below.

(1) Maximum creepage stress (vs. Imp 480 kV)
In the conventional three-dimensional model, for example, five cross sections of the three-core collective insulation connection unit 5 shown in FIG. 8, that is, radial directions at angles of 0 °, 10 ° 20 °, 30 °, 60 ° from the center of the three cores. The straight line drawn on the line connects the intersection point of the outer periphery of the latching step part 8b on which the three bulging parts 9A are erected and the center of the uppermost bulging part 9A (the center of the conductor connection fitting 11). Table 1 shows the maximum value of the creeping stress when Imp 480 kV is applied to five cross sections cut in the same direction along the line. Moreover, the result of the electric field analysis in the cross section of a 0 degree position, a 20 degree position, and a 30 degree position is shown to Fig.9 (a) (b) (c).

  The reason why the creepage stress is high in the cross section of 10 ° to 20 °, while the creepage stress is low in the cross section of 0 °, is considered as follows. That is, at the position of 0 °, as shown in FIG. 9 (a), the center portion of the three centers and the projection root portion (the rising portion of the bulging portion 9A) are smoothly continuous, whereas This is probably because the base of the protrusion has a concave R shape with a small radius at the shifted position. The maximum creepage stress value in the 10 ° and 20 ° cross sections exceeds the allowable (maximum) stress value (12.5 kV / mm) that does not cause dielectric breakdown. Further, the maximum stress along the 30 ° cross section does not exceed the allowable value, but is higher than the 0 ° position. Therefore, at the rising portion of the bulging portion 9A at a portion deviated from 0 °, the projection root portion is not formed as a final shape, as shown by a broken line in FIGS. 9B and 9C, without forming a concave R shape. By forming it on a gently sloping surface, it was possible to fit within the allowable (maximum) stress (see FIGS. 4A and 4B).

(2) Increase in stress due to the shielding cylinder (2-1) Stress concentration (absolute stress) at the tip of the paint (conductive paint) when a gap occurs between the shielding cylinder and the three-core collective insulation connection unit
As a result of confirming the gap generated when the shielding cylinder 7 is fitted on the latching step portion 8b of the flange portion 8 of the three-core collective insulation connection unit 5, the maximum value of the gap due to manufacturing error is 2 mm. It was. At this time, the maximum stress at the front end of the paint at the position of 0 ° increased due to the presence of the gap and became 19.5 kV / mm (vs. Imp 480 kV). However, since the allowable stress of the oil film of 2 mm is 40 kV / mm, it has been confirmed that a safety factor of 2 times or more can be secured even when such a gap is generated. The result of the electric field analysis is shown in FIG. Note that the allowable stress (vs. Imp) of the oil film is τ = 50 × L ^1/3 kV / mm (L: the thickness of the oil film).

(2-2) Stress (absolute stress) just below the sheath cylinder (hanging member 13)
In order to confirm the influence of the sheath cylinder on the electric field, an electric field analysis is performed for each position where the sheath is attached, and the results are compared with the case without the sheath, as shown in FIGS. Shown in

  As a result of the electric field analysis, it was found that the stress directly under the sheath is about 2 to 3.5 times larger than the flat portion. However, the stress immediately below the shear at the 20 ° position (36.7 kV / mm), which is the breaking point, is lower than the allowable stress 50 kV / mm of the 1 mm oil film and is below the allowable value. However, since an increase in stress is not preferable, the sheath is attached at a position where the absolute stress is low (see FIG. 11B).

(2-3) Influence of the above two terms of riding and folding Both of the above (2-1) and (2-2) terms can be used when both are folded, even if they are below the allowable stress. There is concern that the safety factor will fall and exceed the acceptable level. Therefore, in the present embodiment, as a countermeasure, the sheath position is set to 60 ° as described in the section (2-2). Specifically, marking was made at the 60 ° position of the three-core collective insulation connection unit 5 and thorough management of the sheath mounting position during construction was decided.

(3) Summary of causes of high stress and countermeasures As for the cause of high stress, first, a specific high stress (layering stress) occurs at the 20 ° position of the three-core collective insulation connection unit 5. More broadly, at the part where the outer periphery of the base part of the bulging part 9A is separated from the outer periphery of the latching step part 8B of the flange part 8, high stress is generated at the rising part of the bulging part 9A. Therefore, as a countermeasure, the rising portion of the bulging portion 9A and the surface of the latching step portion 8b are not formed on the rising portion (protrusion root) of the bulging portion 9A without forming a concave R shape with a large curvature. Therefore, it is configured to be continuous through a gentle inclined surface. If comprised in this way, it will become difficult to generate | occur | produce local electrical stress concentration in the peripheral part of the standup | rising part of 9 A of bulging parts, and it can avoid a dielectric breakdown. Next, the electrical stress concentration (2-1) generated at the coating tip due to the gap between the shielding cylinder 7 and the latching step portion 8b, and the disturbance of stress (2-2) immediately below the sheath of the shielding cylinder 7 It is thought that the superposition of causes high stress. As a countermeasure, at the time of construction, it was decided to carry out markings and manage so that the sheath is attached at a position of 60 °. Based on such test results, a three-core collective junction box as described above was designed. It should be noted that the present invention is not limited to the embodiment, and can be freely improved, changed, etc. as necessary without departing from the gist of the invention. For example, the three-core collective junction box of the present invention may be applied to connection between OF cables. In that case, the configuration of the three-core collective insulation connection unit and the shielding cylinder may be changed as appropriate.

  The three-core batch type junction box of the present invention is particularly compact in the length direction, reduced in the number of parts, and reduced in weight. Therefore, the workability in the manhole is good. Suitable for replacement construction.

It is sectional drawing of the 3 core collective type | mold connection box which concerns on embodiment of this invention. It is a perspective view of the 3 core collective insulation connection unit. (A) is sectional drawing of the 3 core collective insulation connection unit, (b) is an enlarged view of a concave R part. (A) (b) is sectional drawing of the inclined surface formed between the standup | rising part of the bulging part and the surface of a latching step part in the same different angle. (A) is sectional drawing of the shielding cylinder, (b) is the top view. It is explanatory drawing of the attachment structure of the same metal fitting. It is explanatory drawing which compared the dimension of the 3 core collective type connection box which concerns on embodiment of the same invention, and the conventional 3 core collective type connection box. It is explanatory drawing of the cutting | disconnection location of the 3 core collective insulation connection unit applied to the lightning impulse pressure | voltage resistant test. It is explanatory drawing of the same electric field analysis, (a) is 0 degree, (b) is 20 degrees, (c) shows the data of the cutting part of 30 degrees. It is explanatory drawing of the electric field analysis around the base of the shielding cylinder. (A) is an explanatory view of an electric field analysis of the mounting position of the sheath at a position of 60 ° when the sheath of the shielding cylinder is mounted at a position of 20 °. It is sectional drawing of the conventional 3 core collective connection box.

Explanation of symbols

1 3-core OF cable (OF cable) 2 3-core CV cable (CV cable) 3, 4 Cable core 3a, 4a Conductor 3b, 4b Insulation layer 5 3-core collective insulation connection unit 6 Conductor connection (cable connection)
7 Shielding tube 7a Plate member 7b Reinforcement plate 7c Hooked side 7c, 7c
DESCRIPTION OF SYMBOLS 8 Flange part 8a Connection edge part 8b Engagement step part 9A Expansion part 9B Protrusion part 10 OF side case 10A Base part 10B Tip part 10a Corrosion protection cover 10b Copper pipe 10e Connection ring 11 Conductor connection metal fitting (conductor connection means) 13 Latching member (Saya)
14 Branch point 15 Metal sheath 16 Semi-stop device 16a Branch port 17 Oil passage 18 Communication pipe 19 Semi-stopper valve 20 Core wire holding fitting 21 Connection sleeve 22 Insulating oil-impregnated paper (insulating layer)
23 Metal bell mouth 24 Carbon roll paper 25 Conductor connecting pipe 26 Press fitting 27 Pushing member 28 Pre-mold insulator (Stocon)
29 Spring 30 CV side case (3 or anticorrosion cover)
30a Branch 30e Connection ring
32 CV side main body case 33 spacer 35 terminal member 39 ground terminal 40 main body case r, s concave R portion A length of metal end B length of OF branching portion C length of OF insulating portion D 3-core collective insulation connection Length of unit E Length of CV copper tube portion L1 Overall length of conventional 3-core batch type connection box L2 Overall length of 3-core batch type connection box according to the embodiment of the present invention 51 OF cable 52 CV cable 53, 54 Conductor 55 Oil stop unit 56 Conductor connection fitting 57 Metal sheath 58 Shielding cylinder 59 Main body cover 60 Joint flange 61 Semistop device 62 Oil passage 63 OF side case 64 Semistopper valve

Claims (7)

A three-core batch-type connection box for connecting three-core cables having three cable cores having conductors,
At least one of the three-core cables is an OF cable;
An OF-side case that covers at least the cable connection on the OF cable side in an oil-tight state;
A three-core collective insulation connection unit having an oil stop function with the OF side case, and connecting and holding three opposing conductors in a conductive state under an insulating state ;
The three-core collective insulation connection unit is disposed upright in a direction perpendicular to the conductor connection direction, and a flange portion connected in an oil-tight manner to the OF-side case;
Three bulges that project from the flange toward the conductor connection direction on the OF cable side;
In a three-core collective junction box having a shielding tube that covers an entire conductor connection portion to which three conductors are connected via an insulating layer,
A connection edge to be connected to the ring-shaped connection portion of the OF case is formed on the periphery of the flange portion of the three-core collective insulation connection unit, and the shielding is provided inside the connection edge. A disc-shaped latching step for fitting the base of the tube is formed, and the three bulging portions each formed in a tapered cylindrical shape are erected on the surface of the latching step, The concave R portion formed between the connecting edge portion of the flange portion and the latching step portion is characterized in that a part of the concave R portion is cut inwardly from the peripheral surface of the flange portion and the curvature is set small. 3-core batch connection box. A plurality of outer peripheral surfaces of the tapered cylindrical bulging portion have different curvatures from the rising portion of the bulging portion to the surface of the latching step portion so that dielectric breakdown due to local concentration of electric field stress can be avoided. 3-core-in-one-type connection box according to claim 1, the curved surface of which is characterized in that gentle inclined surface is continuously formed. The gentle inclined surface forms a concave R shape at an angle position where the angle from the center of the flange portion is 10 degrees to 30 degrees with the line connecting the center of the flange and the center of the bulging portion being 0 degrees. The three-core batch type connection box according to claim 2, wherein the three-core connection box is not provided. The three cores collectively insulating connection unit, 3-core-in-one-type connection box according to any one of claims 1 to 3, characterized in that it is formed by integral molding of an epoxy resin. The shielding cylinder, the three cores collectively junction box according to any one of claims 1 to 4, characterized in that it consists of shape-retaining possible half-split shape smooth metal plate member into a cylindrical shape. In order to retain the plate member in a cylindrical shape, the latch member that latches the latched side portions formed on the edge of the plate member is located at an intermediate portion between two adjacent bulging portions. The three-core collective junction box according to claim 5 , wherein the three-core junction box is disposed along the connection box. The three-core batch type connection box according to any one of claims 1 to 6 , wherein the other of the three-core cables is a three-core CV cable.