JP7517100B2 - How to connect the low-voltage power cable to the additional duct - Google Patents

Description

This invention relates to a method for connecting a low-voltage power cable of an additional duct when replacing an existing switchgear with a new switchgear, in order to connect the end of the low-voltage power cable extending from the new switchgear to a copper strip in the additional duct before a power outage (before current is cut off) in the transformer.

Conventionally, a transformer has a transformer body and a transformer case that houses the transformer body. The three-phase (U-phase, V-phase, W-phase) outlet wires (primary side outlet wires) of the high-voltage side winding drawn out from the transformer body are connected to a three-phase high-voltage side power cable. The three-phase outlet wires (secondary side outlet wires) of the low-voltage side winding drawn out from the transformer body are connected to a three-phase low-voltage side power cable. The low-voltage side power cable is connected to a switch gear installed at a position away from the transformer (see Patent Document 1).

Figure 12 is a simplified diagram showing the relationship between the transformer 1, the low-voltage side duct 2 (hereinafter, abbreviated as the duct), and the switch gear 3. As shown in this Figure 12, the low-voltage side power cable 4 extending from the switch gear 3 is laid underground 5, and the end pulled out from the underground 5 is terminated and then connected to a copper band 6 in the duct 2.

Figure 13 shows the duct 2 attached to the transformer 1. Note that Figure 13(a) is a side view of the duct 2, and Figure 13(b) is a front view of the transformer 1 and the duct 2.

As shown in this figure 13, the duct 2 has a horizontal beam section 10 connected to the upper part of the transformer case 7 that houses the transformer main body 1A and extending horizontally (along the surface 8 on which the transformer 1 is installed), and a vertical beam section 11 that extends vertically downward from the end of the horizontal beam section 10. When viewed from the front side, the duct 2 has a roughly L-shaped shape. The lower end of the vertical beam section 11 of the duct 2 is fixed to the duct installation base (foundation) 12. The internal space of the duct 2 contains copper bands 6 for three phases supported by insulators 13. One end of the copper bands 6 for three phases is connected to each phase of the low-voltage side winding 14, and the other end is connected to each phase of the low-voltage side power cable 4.

Figures 14 and 15 are diagrams explaining the conventional construction method when replacing the existing switch gear 3A with a new switch gear 3B. First, as shown in Figure 14, in the first stage of the conventional construction method, while the transformer 1 and the existing switch gear 3A are in operation (before the power outage), the new switch gear 3B is installed in the vacant space, and an additional duct installation base (foundation) 15 is provided on the side facing the side wall 17 of the existing duct 2A and adjacent to the existing duct 2A (see Figure 14).

Next, in the second stage of the conventional construction method, when the power supply to the transformer 1 and the existing switch gear 3A is cut off (when there is a power outage), the side wall 17 of the existing duct 2A is replaced with the side wall 18 for connecting the extension duct on which the overhang duct 2Aa is formed (see FIG. 13). Next, as shown in FIG. 15, the extension duct 2B is placed on the overhang duct installation stand 15, the opening 22 of the cross beam part 21 of the extension duct 2B is aligned with the opening 20 of the overhang duct 2Aa, the copper band 6 is extended from the existing duct 2A side (overhang duct 2Aa side) into the cross beam part 21 of the extension duct 2B, and the extension side flange 23 located on the opening 22 side of the cross beam part 21 of the extension duct 2B and the existing side flange 24 located on the opening 20 side of the overhang duct 2Aa are fixed with a plurality of bolts and nuts (not shown) with a gasket 25 in between. The copper strip 6 extended from the existing duct 2A into the horizontal beam 21 of the extension duct 2B is connected to the copper strip 6 previously installed in the extension duct 2B by a worker who inserts the copper strip 6 through an opening/closing window 26 formed on the upper surface of the horizontal beam 21 of the extension duct 2B. The low-voltage power cable 4 laid from the new switch gear 3B to the vertical beam 16 of the extension duct 2B has a terminal treatment applied to the tip of the portion drawn out from the ground 5. After that, various tests on the new switch gear 3B are performed, and then the tip of the low-voltage power cable that has been subjected to the terminal treatment is connected to the lower end of the copper strip 6 housed in the vertical beam 16 of the extension duct 2B. As a result, the new switch gear 3B is electrically connected to the transformer 1 via the low-voltage power cable 4 and the copper strip 6. The low-voltage power cable 4 connected to the existing switch gear 3A and transformer 1 will be removed after the current to transformer 1 is cut off (after a power outage).

JP 2016-207690 A

However, in the conventional construction method shown in Figures 14 and 15, if the length of each phase of the low-voltage side power cable 4 connected to the copper band 6 in the vertical beam section 16 of the additional duct 2B is inappropriate, it becomes necessary to replace the low-voltage side power cable 4 (redoing the installation work), adjust the length, redo the terminal processing, etc., which results in the problem that it takes time to replace the existing switch gear 3A with the new switch gear 3B on the day of the power outage, and the power outage lasts longer.

Therefore, the present invention provides a method for connecting the low-voltage side power cable of an additional duct that can shorten the power outage time during switchgear replacement work.

The present invention relates to a method for connecting a low-voltage power cable of an extension duct 2B, in which an extension duct 2B is connected to an existing duct 2A attached to a transformer case 7 that houses a transformer 1 when replacing an existing switch gear 3A with a new switch gear 3B, a second copper band 6B connected to a first copper band 6A on the existing duct 2A side is placed inside the extension duct 2B, and the tip of a low-voltage power cable 4 extending from the new switch gear 3B is connected to the lower end of the second copper band 6B. In the present invention, the extension duct 2B has a lower part 2Ba that is installed in advance on a foundation 15 when the transformer 3 and the existing switch gear 3A are in operation, and an upper part 2Bb that is placed on the lower part 2Ba and connected to the existing duct 2A when the transformer 1 is in a power outage. In addition, the lower portion 2Ba is configured so that an upper opening 73 on which the upper portion 2Bb is placed is closed with a lid 70 before the upper portion 2Bb is placed. In addition, if the part of the second copper band 6B placed in the lower portion 2Ba is the second copper band lower end portion 6Ba, this second copper band lower end portion 6Ba is separated from the other part of the second copper band placed in the upper portion 2Bb (the part 6Bb other than the second copper band lower end portion) and this separated second copper band lower end portion 6Ba is fixed to the lower portion 2Ba in a state where it is positioned by the lid 70 and a positioning jig 71 attached to the lid 70. Then, the tip of the low-voltage side power cable 4 is connected to the second copper band lower end portion 6Ba after terminal processing is performed and after the second copper band lower end portion 6Ba is fixed to the lower portion 2Ba.

According to the method for connecting the low-voltage side power cable of the expansion duct of the present invention, the end of the low-voltage side power cable extending from the new switchgear is terminated before the transformer goes out of power, and then the end of the terminated low-voltage side power cable is connected to the lower end portion of the second copper band that is accurately positioned and fixed within the lower part of the expansion duct. This eliminates the need to adjust the length of the low-voltage side power cable or redo the termination process when the transformer goes out of power, and makes it possible to shorten the time required to replace the existing switchgear with the new switchgear on the day of the power outage.

1A and 1B are diagrams showing a duct connection structure of a transformer according to an embodiment of the present invention, in which FIG. 1A is a front view of an additional duct, and FIG. 1B is a side view of an existing duct, an extension duct, and an additional duct. 1B is an enlarged view of part B1 of FIG. 1B, showing a connection between the extension duct and the additional duct with a part cut away. FIG. 3(a) and 3(b) are views of a cover that covers the connecting bolt mechanism, with FIG. 3(a) being a front view of the cover, FIG. 3(b) being a right side view of the cover, FIG. 3(c) being a left side view of the cover, FIG. 3(d) being a bottom view of the cover, FIG. 3(e) being a top view of the cover, and FIG. 3(f) being a cross-sectional view taken along line A1-A1 in FIG. 3(a). 4A is a side view of the additional duct (with the copper band and insulators omitted), FIG. 4B is a front view of the additional duct, and FIG. 4C is a plan view of the additional duct. FIG. 5(a) is a plan view showing a pair of connecting stays in use (viewed along the C1 direction of FIG. 4(a)), FIG. 5(b-1) is a plan view of the first stay, FIG. 5(b-2) is a front view of the first stay, FIG. 5(b-3) is a side view of the first stay, FIG. 5(c-1) is a plan view of the third stay fixed across the first and second stays, FIG. 5(c-2) is a left side view of the third stay, and FIG. 5(c-3) is a rear view of the third stay. 6A and 6B are diagrams showing an existing duct and an extending duct attached to the existing duct (copper bands and insulators are omitted), where FIG. 6A is a front view of the existing duct and the extending duct, FIG. 6B is a side view of the existing duct and the extending duct, and FIG. 6C is a plan view of the existing duct and the extending duct. Figure 7(a) is a front view of the lower part of the vertical beam part to which the lid and positioning jig are attached, Figure 7(b) is a side view of the lower part of the vertical beam part to which the lid and positioning jig are attached, and Figure 7(c) is a plan view of the lower part of the vertical beam part to which the lid and positioning jig are attached. Figure 8(a) is a front view of the lower part of the vertical beam section to which only the positioning jig is attached, Figure 8(b) is a side view of the lower part of the vertical beam section to which only the positioning jig is attached, and Figure 8(c) is a plan view of the lower part of the vertical beam section to which only the positioning jig is attached. 9(a) is a front view of the lid assembly (the lid with a positioning jig attached), FIG. 9(b) is a side view of the lid assembly, FIG. 9(c) is a plan view of the lid assembly, and FIG. 9(d) is a back view of the lid assembly. 10(a) is a front view of the lid with a portion of the lid cut away, FIG. 10(b) is a side view of the lid with a portion of the lid cut away, FIG. 10(c) is a plan view of the lid, and FIG. 10(d) is a back view of the lid. 11(a) is a front view of the positioning jig, FIG. 11(b) is a side view of the positioning jig, FIG. 11(c) is a plan view of the positioning jig, and FIG. 11(d) is a back view of the positioning jig. FIG. 2 is a diagram showing a simplified relationship between a switchgear, a duct, and a transformer. 13A and 13B are diagrams showing a duct attached to a transformer body, in which FIG. 13A is a side view of the duct and FIG. 13B is a front view of the duct. FIG. 1 is a diagram illustrating a conventional construction method (first stage) for replacing an existing switchgear with a new switchgear. FIG. 1 is a diagram illustrating a conventional construction method (second stage) for replacing an existing switchgear with a new switchgear.

The following describes an embodiment of the present invention in detail with reference to the drawings.

Figure 1 is a diagram for explaining a method for connecting a low-voltage side power cable of an additional duct according to an embodiment of the present invention. Note that Figure 1(a) is a side view of an existing duct 2A and an additional duct 2B that constitute a duct 2, and Figure 1(b) is a front view of the additional duct 2B.

(Outline of duct configuration)
The duct shown in FIG. 1 has a connection structure between an existing duct 2A and an additional duct 2B which is different from the conventional connection structure between an existing duct 2A and an additional duct 2B shown in FIG.

(Existing duct)
In Fig. 1, the side wall 17 facing the additional duct 2B has been removed from the existing duct 2A, and a side wall 18 for connecting the additional duct has been attached in place of the side wall 17 (see Fig. 15). The side wall 18 for connecting the additional duct has a protruding duct 2Aa extending toward the additional duct 2B (extending toward the left in Fig. 1(b)) at the same height as the horizontal beam portion 10 of the existing duct 2A (see Fig. 6). The existing duct 2A also has a vertical beam portion 11 standing up from the duct installation base (foundation) 12, and a horizontal beam portion 10 extending from the upper end portion of the vertical beam portion 11 toward the transformer 1. The first copper band 6 for three phases is accommodated in the space within the horizontal beam portion 10 while being supported by the insulators 13. The first copper belts 6 for the three phases are electrically connected at one end to each phase of the low-voltage side winding 14 of the transformer 1, and at the other end to each of the second copper belts 6 for the three phases in the horizontal beam portion 21 of the additional duct 2B. The first low-voltage side power cables (three-phase cables) extending from the existing switchgear have their ends connected to the lower ends of the first copper belts 6 for the three phases in the vertical beam portion 11 of the existing duct 2A, but are removed from the existing duct 2A during the power outage work or after the switching work to the new switchgear is completed. The first copper belts 6 of the vertical beam portion 11 of the existing duct 2A are disconnected from the transformer 1 (transformer main body 1A) during the power outage work. Therefore, the removal work of the existing switch gear and the first low-voltage side power cable 4 can be performed even after the transformer 1 is energized after the switching work to the new switch gear is completed.

(Extending duct)
As shown in Figures 1, 2, and 6, the overhanging duct 2Aa has a shape in which the cross beam portion 10 of the existing duct 2A is extended toward the additional duct 2B, and has a first open end 28 that opens toward the additional duct 2B, and a first flange portion 30 that overhangs along the outer edge of the first open end 28. The first flange portion 30 is formed in a frame shape along the outer edge of the first open end 28 of the overhanging duct 2Aa, and bolt holes 31 are formed at each of the four corners. The overhanging duct 2Aa also has a rectangular space 32 that communicates with the cross beam portion 10 of the existing duct 2A, and the copper strip 6 extending from the cross beam portion 10 side of the existing duct 2A is accommodated inside.

(Additional duct)
As shown in Figures 1 and 4, the expansion duct 2B has a vertical beam portion 16 that stands up from the expansion duct installation base (foundation) 15 so as to be parallel to the expansion duct connection side wall 18, and a horizontal beam portion 21 that extends from the upper end portion of this vertical beam portion 16 in the opposite direction to the extension direction of the extension duct 2Aa.

(Beam part of additional duct)
The cross beam portion 21 of the additional duct 2B is formed so as to be disposed at the same height as the overhang duct 2Aa, has a second opening end 33 that opens opposite the first opening end 28 of the overhang duct 2Aa, and has a second flange portion 34 that overhangs along the outer edge of the second opening end 33. The second flange portion 34 is formed in a frame shape along the outer edge of the second opening end 33 of the cross beam portion 21 (formed in the same shape as the first flange portion 30), and has bolt holes 31 formed at each of the four corners (formed at positions opposite the bolt holes 31 of the first flange portion 30). The cross beam portion 21 of the additional duct 2B also has a rectangular space 35 that communicates with the overhang duct 2Aa, and the second copper strip 6 that is connected to the first copper strip 6 on the overhang duct 2Aa side is housed inside.

(Vertical beam of additional duct)
1 and 4, the vertical beam portion 16 of the additional duct 2B has a lower portion 2Ba fixed onto the additional duct installation base 15, and an upper portion 2Bb fixed onto the lower portion 2Ba (fastened with a plurality of bolts). The above-mentioned horizontal beam portion 21 is integrally formed on the upper end side of the upper portion 2Bb of the vertical beam portion 16.

7 to 11 are diagrams for explaining the configuration of the lower portion 2Ba of the vertical beam portion 16 of the additional duct 2B, and the method of connecting the second copper band lower end portion 6Ba attached to the lower portion 2Ba of the vertical beam portion 16 with the low-voltage power cable 4 extending from the new switch gear 3B. Note that Fig. 7(a) is a front view of the lower portion 2Ba of the vertical beam portion 16 to which the lid 70 and the positioning jig 71 are attached, Fig. 7(b) is a side view of the lower portion 2Ba of the vertical beam portion 16 to which the lid 70 and the positioning jig 71 are attached, and Fig. 7(c) is a plan view of the lower portion 2Ba of the vertical beam portion 16 to which the lid 70 and the positioning jig 71 are attached. 8(a) is a front view of the lower portion 2Ba of the vertical beam portion 16 to which only the positioning jig 71 is attached, FIG. 8(b) is a side view of the lower portion 2Ba of the vertical beam portion 16 to which only the positioning jig 71 is attached, and FIG. 8(c) is a plan view of the lower portion 2Ba of the vertical beam portion 16 to which only the positioning jig 71 is attached. Also, FIG. 9(a) is a front view of the lid assembly 72 (an object in which the positioning jig 71 is attached to the lid 70), FIG. 9(b) is a side view of the lid assembly 72, FIG. 9(c) is a plan view of the lid assembly 72, and FIG. 9(d) is a back view of the lid assembly 72. 10(a) is a front view of the lid 70 with a portion of the lid 70 cut away, FIG. 10(b) is a side view of the lid 70 with a portion of the lid 70 cut away, FIG. 10(c) is a plan view of the lid 70, and FIG. 10(d) is a back view of the lid 70. 11(a) is a front view of the positioning jig 71, FIG. 11(b) is a side view of the positioning jig 71, FIG. 11(c) is a plan view of the positioning jig 71, and FIG. 11(d) is a back view of the positioning jig 71.

The lower portion 2Ba of the vertical beam portion 16 of the additional duct 2B is placed on the additional duct installation base 15 in advance when the transformer 1 and the existing switch gear 3A are in operation (before the power outage and before the upper portion 2Bb of the vertical beam portion 16 of the additional duct 2B is placed on it). At this stage, the lower portion 2Ba of the vertical beam portion 16 can be moved on the additional duct installation base 15, and is not fixed to the additional duct installation base 15 by installation bolts (not shown).

In addition, an upper opening 73 that opens upward (in the normal direction to the installation surface of the additional duct 2B on the additional duct installation stand 15) is formed in the lower portion 2Ba of the vertical beam portion 16 at the upper portion on which the upper portion 2Bb of the vertical beam portion 16 is placed. The second copper band 6B extending from the upper portion 2Bb of the vertical beam portion 16 to the inside of the lower portion 2Ba of the vertical beam portion 16 is separated from the other portion 6Bb of the second copper band 6B by the lower end portion 6Ba of the second copper band 6B (the portion located in the lower portion 2Ba), which is the portion that passes through the upper opening 73 of the lower portion 2Ba of the vertical beam portion 16 and extends to the inside of the lower portion 2Ba of the vertical beam portion 16. The separated lower end portion 6Ba of the second copper band is positioned by the positioning jig 71 attached to the lid 70 (positioned so that the lower end position of the second copper band lower end portion 6Ba coincides with the lower end position of the second copper band 6B), and is fixed to the inside of the lower portion 2Ba of the vertical beam portion 16 by the insulator 13.

(Relationship between the lower part of the vertical beam and the lid and positioning jig)
The lid 70 closes the upper opening 73 of the lower part 2Ba of the vertical beam part 16 until the upper part 2Bb of the vertical beam part 16 is placed on the lower part 2Ba of the vertical beam part 16, and prevents small animals, rain, water droplets, dust, etc. from entering the inside of the lower part 2Ba of the vertical beam part 16 through the upper opening 73 of the lower part 2Ba of the vertical beam part 16. A positioning jig 71 is attached to the inside of the lid 70. The positioning jig 71 has a fixing protrusion 74 formed on the upper surface side fixed to a support protrusion 75 extending from the inner surface of the lid 70 with a bolt and nut 76, and is adapted to fit into the inner peripheral surface of the upper opening 73 of the vertical beam part 16 with a small gap. The positioning jig 71 is formed with three positioning holes 77 through which the second copper strip lower end portions 6Ba of the three phases pass, allowing each second copper strip lower end portion 6Ba to be accurately positioned inside the lower portion 2Ba of the vertical beam portion 16. The positioning jig 71 also has a pair of fixing protrusions 74, 74 formed adjacent to each positioning hole 77, which guide the upper portion of the second copper strip lower end portion 6Ba to move smoothly inside the positioning hole 77, allowing the pair of fixing protrusions 74, 74 and the positioning hole 77 to support the posture of the second copper strip lower end portion 6Ba in the correct position. The second copper band lower end portion 6Ba inserted into the positioning hole 77 of the positioning jig 71 has its upper end abutted against the inner surface 70a of the lid 70, thereby positioning the upper end position and the lower end position, and the attachment position of the tip of the second low-voltage side power cable 4 extending from the new switchgear 3B into the additional duct 2B is accurately positioned. In this way, the second copper band lower end portion 6Ba positioned by the lid 70 and the positioning jig 71 attached to the lid 70 is accurately fixed inside the lower portion 2Ba of the vertical beam portion 16 by the insulator 13.

The second low-voltage side power cable 4 extending from the new switch gear 3B to the additional duct 2B has its length adjusted and its end terminated when the existing switch gear 3A and transformer 1 are in operation (before the power outage), and a predetermined electrical test is performed. As described above, the second copper band lower end portion 6Ba is accurately fixed inside the lower part 2Ba of the additional duct 2B, and then the terminated end is crimped and fixed (crimped) to the connection terminals 78, 78 installed at the lower end of the second copper band lower end portion 6Ba. In this way, the second low-voltage side power cable 4 extending from the new switch gear 3B is connected to the second copper band lower end portion 6Ba in the lower part 2Ba of the additional duct 2B when the existing switch gear 3A and transformer 1 are in operation (before the power outage). The second low-voltage power cable 4 is buried underground from the new switch gear 3B to the vicinity of the additional duct 2B, and the portion (tip) that is pulled out from the ground to the ground near the additional duct 2B is housed in the internal space of the additional duct 2B.

When the transformer 1 is powered out and before the upper part 2Bb is placed on the lower part 2Ba, the cover 70 and the positioning jig 71 are removed from the upper opening 73 of the lower part 2Ba and separated from the lower end part 6Ba of the second copper band. Then, the flange part 81 provided to protrude from the lower end of the upper part 2Bb of the vertical beam part 16 of the additional duct 2B is placed on the flange part 80 provided to protrude from the upper end of the lower part 2Ba of the vertical beam part 16 of the additional duct 2B. At this stage, the flange part 80 of the lower part 2Ba of the vertical beam part 16 and the flange part 81 of the upper part 2Bb of the vertical beam part 16 are not fixed with bolts and nuts (not shown), so that the upper part 2Bb of the vertical beam part 16 can be slid relative to the lower part 2Ba of the vertical beam part 16. In addition, the lid assembly belt 72 (lid 70 and positioning jig 71) has a pair of handles 82, 82 on the upper surface of the lid 70, so that it can be easily removed from the upper opening 73 of the lower portion 2Ba of the vertical beam portion 16 by grasping and lifting the handles 82, 82. Note that the lid assembly 72 is not limited to the configuration of this embodiment, and for example, the lid 70 and the positioning jig 71 may be integrally formed by welding or the like.

(Connection between extension duct and additional duct)
1 and 2, a gap 36 is provided between the first flange portion 30 of the overhang duct 2Aa and the second flange portion 34 of the extension duct 2B to absorb variations in the distance between the overhang duct 2Aa and the extension duct 2B (for example, installation errors of the extension duct 2B relative to the existing duct 2A, installation errors of the extension duct 2B relative to the overhang duct 2Aa, etc.). The first flange portion 30 of the overhang duct 2Aa and the second flange portion 34 of the extension duct 2B are fixed by a plurality of connecting bolt mechanisms 37 whose length can be adjusted according to the size of the gap 36. The first flange portion 30, the second flange portion 34, the gap 36, and the plurality of connecting bolt mechanisms 37 are covered by a cover 38.

(Connection bolt mechanism)
1, 2, 4, and 6, the connecting bolt mechanism 37 is disposed at each of the four corners of the first flange portion 30 and the second flange portion 34. The connecting bolt mechanism 37 includes a connecting bolt 40 having a shaft portion 40a inserted into the bolt hole 31 of the first flange portion 30 and the bolt hole 31 of the second flange portion 34, a connecting nut 41 screwed onto the shaft portion 40a of the connecting bolt 40 and sandwiching the first flange portion 30 and the second flange portion 34 between the connecting nut 41 and the head portion 40b of the connecting bolt 40, a first locking nut 44 sandwiching the second flange portion 34 between the head portion 40b of the connecting bolt 40 via a first vibration isolating rubber 42 and a second vibration isolating rubber 43, and a second locking nut 45 sandwiching the first flange portion 30 between the connecting nut 41 and the head portion 40b of the connecting bolt 40. In addition, in the connecting bolt mechanism 37, a washer 46 is sandwiched between the head 40b of the connecting bolt 40 and the first vibration isolating rubber 42, and a washer 46 is sandwiched between the first locking nut 44 and the second vibration isolating rubber 43, so that the first vibration isolating rubber 42 can be prevented from being damaged by the head 40b of the connecting bolt 40, and the second vibration isolating rubber 43 can be prevented from being damaged by the first locking nut 44. The first vibration isolating rubber 42 is formed into a cylindrical shape from, for example, synthetic rubber (chloroprene rubber, etc.), and is sandwiched between the head 40b of the connecting bolt 40 and the second flange portion 34 in a state where it is fitted onto the shaft portion 40a of the connecting bolt 40. The second vibration isolating rubber 43 is formed into the same shape as the first vibration isolating rubber 42 from the same material as the first vibration isolating rubber 42, and is sandwiched between the first locking nut 44 and the second flange portion 34. Such a connecting bolt mechanism 37 adjusts its length according to the size of the gap 36 between the first flange portion 30 of the overhang duct 2Aa and the second flange portion 34 of the additional duct 2B, and can reliably fix the first flange portion 30 (overhang duct 2Aa) and the second flange portion 34 (additional duct 2B), while suppressing the transmission of vibrations from the transformer case 7 and the existing duct 2A (overhang duct 2Aa) to the additional duct 2B. Note that the connecting bolt mechanism 37 may be configured such that the orientation of the connecting bolt 40 is reversed from that of the above embodiment, a first vibration-proof rubber 42 is disposed between the head 40b of the connecting bolt 40 and the first flange portion 30, and a second vibration-proof rubber 43 is disposed between the first flange portion 30 and the second lock nut 45. In addition, the bolt holes 31 of the first flange portion 30 and the bolt holes 31 of the second flange portion 34 are formed larger than the shaft portion 40a of the connecting bolt 40 so as to absorb any positional misalignment between the bolt holes 31 of the first flange portion 30 and the bolt holes 31 of the second flange portion 34.

(cover)
1, 2, and 3, the cover 38 is assembled by combining the first frame 47 and the second frame 48, each of which has a U-shaped cross section and an L-shaped front shape, so that the front shape is rectangular, and is attached across the extension duct 2Aa and the extension duct 2B so as to cover the first flange portion 30 of the extension duct 2Aa, the gap 36, the second flange portion 34 of the extension duct 2B, and the multiple connection bolt mechanisms 37. The second frame 48 has a smaller width than the first frame 47, and one and the other ends of the second frame 48 are fitted into the space of the first frame 47, and the one and the other ends of the second frame 48 are screwed and fixed to the first frame 47. The cover 38 is fixed to the outer surfaces of the extension duct 2Aa and the extension duct 2B with multiple screws. Such a cover 38 can prevent small animals, rainwater, dust, etc. from entering the extension duct 2Aa, the existing duct 2A, and the additional duct 2B through the gap 36 between the first flange portion 30 of the extension duct 2Aa and the second flange portion 34 of the additional duct 2B.

(Connecting stay)
1, 4 to 6, the side wall 50 (side wall 50 facing the side wall 18 for connecting the extension duct) of the vertical beam portion 16 of the extension duct 2B and the side wall 18 for connecting the extension duct are fixed by a pair of connection stays 51 arranged back to back along the width direction, assuming that the rising direction of the side wall 50 of the vertical beam portion 16 of the extension duct 2B is the height direction, the direction perpendicular to the height direction and along the side wall 50 is the width direction, and the direction perpendicular to the side wall 50 (direction along the protruding direction of the protruding duct 2Aa) is the connection direction. The connection stays 51 have a first stay 52 fixed to the side wall 50 of the vertical beam portion 16 of the extension duct 2B, a second stay 53 fixed to the side wall 18 for connecting the extension duct, and a third stay 54 connecting the first stay 52 and the second stay 53. One end of the third stay 54 is fastened to the first stay 52 by a first bolt 55 and a first nut 56. The other end of the third stay 54 is fastened to the second stay 53 by a second bolt 57 and a second nut 58.

The first stay 52 is an angle-shaped member, with one side 52a perpendicular to the side wall 50 of the vertical beam portion 16 of the additional duct 2B and extending along the width direction, and the other side 52b perpendicular to the one side 52a and extending downward in the height direction (downward in FIG. 4(a)). A pair of elongated first bolt insertion holes 60 are formed along the width direction in the other side 52b of the first stay 52. The shaft portion of the first bolt 55 is inserted into the pair of first bolt insertion holes 60, 60.

The second stay 53 is an angle-shaped member, one end of which is fixed to the side wall 18 for connecting to the additional duct, and which extends in a direction (connection direction) perpendicular to the side wall 18 for connecting to the additional duct. The second stay 53 is installed at the same height as the first stay 52, with one side 53a positioned along the width direction and the other side 53b positioned along the height direction. A pair of third bolt insertion holes 61, which are elongated in the height direction, are formed in the other side 53b of the second stay 53 along the connection direction. The shafts of the second bolts 57 are inserted into the pair of third bolt insertion holes 61, 61.

The third stay 54 has an L-shape in plan view, and is shaped like a first angle member 62 extending along the width direction and a second angle member 63 extending along the connection direction integrated together. The third stay 54 is installed at the same height as the first stay 52 and the second stay 53, and one side 62a of the first angle member 62 located on one end side of the third stay 54 abuts against the other side 52b of the first stay 52, and the other end side of one side 63a of the second angle member 63 abuts against the other side 53b of the second stay 53. A pair of elongated second bolt insertion holes 64 are formed along the width direction on one side 62a of the first angle member 62. These pair of second bolt insertion holes 64, 64 are positioned corresponding to the first bolt insertion hole 60 of the first stay 52, and the shaft portion of the first bolt 55 inserted into the first bolt insertion hole 60 is inserted through them. A pair of elongated fourth bolt insertion holes 65 are formed along the connection direction on the other end side of one side 63a of the second angle member 63. The pair of fourth bolt insertion holes 65 are positioned to correspond to the third bolt insertion holes 61 of the second stay 53, and the shaft portion of the second bolt 57 inserted into the third bolt insertion hole 61 is inserted into the fourth bolt insertion holes 65.

The connection stay 51 with the above structure allows misalignment in the connection direction, width direction, and height direction between the extension duct 2Aa fixed to the existing duct 2A and the additional duct 2B, and can reliably fix the extension duct 2Aa fixed to the existing duct 2A and the additional duct 2B.

In this embodiment, the work of connecting the additional duct 2B and the extending duct 2Aa using the connection bolt mechanism 37, fixing the additional duct 2B and the existing duct 2A with the connection stay 51, fixing the lower part 2Ba and the upper part 2Bb of the vertical beam part 16 of the additional duct 2B with multiple bolts and nuts (not shown), and fixing the lower part 2Ba of the vertical beam part 16 of the additional duct 2B to the additional duct installation base 15 with multiple installation bolts (not shown) is carried out in parallel and with adjustments.

Then, after the work of connecting the additional duct 2B and the extending duct 2Aa with the connecting bolt mechanism 37, fixing the additional duct 2B and the existing duct 2A with the connecting stays 51, fixing the lower part 2Ba and the upper part 2Bb of the vertical beam section 16 of the additional duct 2B with a plurality of bolts and nuts (not shown), and fixing the lower part 2Ba of the vertical beam section 16 of the additional duct 2B to the additional duct installation base 15 with a plurality of mounting bolts (not shown) is completed, the first copper band 6A on the existing duct 2A side and the second body band 6B on the additional duct 2B side are connected via a connecting copper band 83 formed of a plurality of copper wires so as to be deformable in three dimensions. In addition, the second copper band lower end portion 6Ba on the lower portion 2Ba side of the additional duct 2B and the second copper band 6B on the upper portion 2Bb side of the additional duct 2B (the portion 6Bb of the second copper band 6B other than the lower end portion of the second copper band) are connected via a connecting copper band 83 formed of multiple copper wires so that they can be deformed three-dimensionally.

(Effects of the embodiment)
As described above, according to the low-voltage side power cable connecting method of the extension duct 2B of this embodiment, before a power outage of the transformer 1, the end of the second low-voltage side power cable 4 extending from the new switch gear 3B is subjected to terminal processing, and then the end of the terminal-processed low-voltage side power cable 4 is connected to the second copper band lower end portion 6Ba accurately positioned and fixed within the lower portion 2Ba of the extension duct 2B. This makes it unnecessary to adjust the length of the low-voltage side power cable 4 and redo the terminal processing when the transformer 1 experiences a power outage, and makes it possible to shorten the time required for the replacement work of the existing switch gear 3A with the new switch gear 3B on the day of the power outage.

Furthermore, according to the method for connecting the low-voltage side power cable of the expansion duct 2B of this embodiment, even if the lower part 2Ba of the vertical beam part 16 of the expansion duct 2B is installed in advance when the transformer 1 and the existing switch gear 3A are activated (before a power outage), by blocking the upper opening 73 of the lower part 2Ba of the expansion duct 2B with the lid assembly 72 (lid 70 and positioning jig 71), it is possible to prevent small animals, rainwater, dust, etc. from entering the lower part 2Ba of the expansion duct 2B, and the lid assembly 72 can position the lower end part 6Ba of the second copper band, making it possible to reliably connect the second low-voltage side power cable 4 to the lower end part 6Ba of the second copper band. In addition, according to the low-voltage power cable connection method for the expansion duct 2B of this embodiment, when the transformer 1 is powered out and before the upper part 2Bb is placed on the lower part 2Ba, the lid assembly 72 (lid 70 and positioning jig 71) is removed from the upper opening 73 of the lower part 2Ba and separated from the lower end part 6Ba of the second copper band, so that the lower part 2Ba of the expansion duct 2B and the upper part 2Bb of the expansion duct 2B can be assembled smoothly.

In addition, according to the low-voltage power cable connection method for the expansion duct 2B of this embodiment, the lower end portion 6Ba of the second copper band arranged in the lower part 2Ba of the expansion duct 2B and the other part of the second copper band 6B arranged in the upper part 2Bb (the part 6Bb other than the lower end portion of the second copper band) are connected via a deformable connecting copper band 83. Therefore, even if there is a positional misalignment between the lower end portion 6Ba of the second copper band and the part 6Bb other than the lower end portion of the second copper band, the lower end portion 6Ba of the second copper band and the part 6Bb other than the lower end portion of the second copper band are reliably connected, and the lower part 2Ba of the expansion duct 2B and the upper part 2Bb of the expansion duct 2B can be smoothly assembled.

(Modification of Duct Connection Structure)
The connection structure of the duct 2 secures the side wall 18 for connecting to the additional duct and the side wall 50 of the additional duct 2B by a pair of connection stays 51, 51 arranged in two locations, but is not limited to this, and the side wall 18 for connecting to the additional duct and the side wall 50 of the additional duct 2B may be secured by a connection stay 51 arranged in only one location.

The connection structure of the duct 2 is not limited to the above embodiment, and may be such that a first bolt insertion hole 60 having an elongated shape along the height direction is formed in one of the ends of the third stay 54 and the first stay 52, a second bolt insertion hole 64 having an elongated shape along the width direction is formed in the other of the ends of the third stay 54 and the first stay 52, a third bolt insertion hole 64 having an elongated shape along the connection direction is formed in the other end of the third stay 54 and the second stay 53, and a fourth bolt insertion hole 65 having an elongated shape along the height direction is formed in the other end of the third stay 54 and the second stay 53.

1... transformer, 1A... transformer body, 2A... existing duct, 2B... additional duct, 2Ba... lower part, 2Bb... upper part, 3A... existing switch gear, 3B... new switch gear, 4... low-voltage power cable, 6A... first copper band, 6B... second copper band, 6Ba... lower end part of second copper band, 6Bb... parts other than the lower end part of second copper band, 15... foundation (additional duct installation stand), 70... lid, 71... positioning jig, 73... upper opening

Claims (3)

A method for connecting a low-voltage side power cable of an additional duct, in which an additional duct is connected to an existing duct attached to a transformer case that houses a transformer when replacing an existing switchgear with a new switchgear, a second copper band that is connected to a first copper band on the existing duct side is disposed on the inside of the additional duct, and a tip of a low-voltage side power cable extending from the new switchgear is connected to a lower end of the second copper band,
The additional duct has a lower portion that is installed in advance on a foundation when the transformer and the existing switchgear are operated, and an upper portion that is placed on the lower portion and connected to the existing duct when the transformer is powered off,
The upper opening of the lower part is covered with a lid until the upper part is placed on the lower part.
When the portion of the second copper strip arranged in the lower portion is defined as a lower end portion of the second copper strip, the lower end portion of the second copper strip is separated from the other portion of the second copper strip arranged in the upper portion, and the separated lower end portion of the second copper strip is fixed to the lower portion while being positioned by the lid and a positioning jig attached to the lid,
the end of the low-voltage power cable is connected to the second copper strip lower end portion after terminal processing is performed and after the second copper strip lower end portion is fixed to the lower portion;
A method for connecting a low-voltage side power cable of an extension duct. The lid and the positioning jig are removed from the upper opening of the lower part and separated from the second copper strip lower end part when the transformer is turned off and before the upper part is placed on the lower part.
2. The method for connecting a low-voltage side power cable of an extension duct according to claim 1. the lower end portion of the second copper strip is connected to another portion of the second copper strip disposed in the upper portion via a deformable connecting copper strip;
3. The method for connecting a low-voltage side power cable of an extension duct according to claim 2.

Images