JPH0228561Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to a bushing cap that is attached to a bushing of a distribution pole transformer. [Prior Art] As shown in FIG. 1, a leadless stud-type bushing 1 in a pole-mounted power distribution transformer has a recess 2 at its tip, and a terminal 3 made of a threaded connection fitting is installed in the recess 2. A wire insertion hole 4 is provided in the terminal 3, and a notch 5 is provided in a part of the peripheral wall of the recess 2 facing the wire insertion hole 4. The wire is inserted into the wire insertion hole 4 through the notch 5 and fixed by tightening the presser knob 6. In the above bushing, a gap is created between the peripheral wall of the recess 2 and the knob 6, and a gap is also created between the notch 5 and the electric wire passing therethrough. As a result, insects may enter these gaps, and birds that follow the insects may come into contact with live parts, or snakes or trees may come into contact with live parts, which is one of the causes of ground faults. It's getting old. As one means for solving the above-mentioned problems, there is a method disclosed in Japanese Utility Model Application Publication No. 163720/1983 as "Bird Damage Prevention Cover for Transformer". As shown in FIG. 11, this includes a C-shaped cover 40 that covers the recess 2 of the bushing 1 (see FIG. 1), and a cylindrical cover 41 that is inserted into the notch 5 for inserting the electric wire. and two arms 42 are provided at the inner end of the cylindrical cover 41 to sandwich both sides of the terminal 3. The cylindrical cover 41 has a longitudinal abutting portion 43 formed therein. [Problems to be Solved by the Invention] The bird damage prevention cover shown in the above-mentioned publication has a drawback in that the open portion 44 of the cover 40 cannot function as a cover because the cover 40 is C-shaped. Further, if there are variations in the outer diameter of the knob 45 due to differences in manufacturers, etc., there will be a mismatch with the inner diameter of the cover 40, causing a gap. The arm 42 has a positioning function, but since it directly touches the terminal 3, which is a live part, it has the drawback that leakage current is likely to flow, impairing the performance of the bushing. Furthermore, if there is variation in the size of the recess 6,
A gap is created between the recess 6 and the cylindrical cover 41 inserted therein, resulting in an incomplete cover. Furthermore, when inserting an electric wire into the cylindrical cover 41,
Since the abutting portion 43 is forcibly pushed open and the wire is pushed in, there is a risk of damaging the insulator of the wire. Therefore, this invention aims to solve these problems. [Means for Solving the Problem] In order to achieve the above object, this invention provides a terminal 3 having a wire insertion hole 4 protruding from the center of the tip recess 2, attaches a wire holding knob 6 to the terminal 3, In the bushing cap attached to the bushing 1 for the primary terminal of a pole transformer, which has a notch 5 for inserting electric wires in the peripheral wall of the recess 2, the bushing cap is butted against a part of the annular cover 7 that covers the upper end of the bushing 1. The annular cover 7 is provided with an end 15', and the peripheral wall 15 becomes annular by abutting the abutting ends 15', and a pair of semi-annular covers 7a, 7b.
A bendable hinge portion 9 is formed in a portion of the peripheral wall 15 facing the abutting end 15',
Peripheral wall 15 between abutting end 15' and hinge part 9
The above-mentioned semi-annular covers 7a, 7b are formed on the upper end edge, a plurality of tongue pieces 12 are formed on the inner peripheral edge of each semi-annular cover 7a, 7b, and the abutting end 15' of the peripheral wall 15 is formed.
Front hanging parts 16a, 16b extending downward along the outer peripheral surface of the bushing 1 are formed at the side ends, and half-split cylindrical covers 8a, 8b forming the cylindrical cover 8 are formed on the front hanging parts 16a, 16b. are integrally formed, and one of the half-split cylindrical covers 8a and 8b has engagement pieces 26 and 27, and the other half has engagement holes 20 and 27 opposite thereto.
21, and a plurality of flexible protrusions 30, which are in contact with the electric wires, are formed on the inner surface of the tip end of each half-cylindrical cover 8a, 8b.
31 is formed. [Operation] After inserting the primary side (high voltage side) wire of the pole transformer into the wire insertion hole 4 of the terminal 3 through the notch 5,
Operate presser foot knob 6 to tighten the wire. The bushing cap opens wide left and right around the hinge part 9 and is fitted onto the upper end of the bushing 1, so that the peripheral wall 15 of the bushing cap is aligned with the outer peripheral surface of the upper end of the bushing 1, and each semi-annular cover 7a, 7b covers the upper surface of the recess 2. The tongue pieces 12 of the semi-annular covers 7a, 7b are pressed against the base 6a of the knob 6 and curved. The cylindrical cover 8 covers the electric wire, and its projecting piece 31 allows the electric wire to vibrate freely, and at the same time closes the gap between the electric wire and the inner surface of the cylindrical cover 8. [Embodiment] As shown in the attached drawings, the bushing cap according to this invention can be roughly divided into an annular cover 7.
and a cylindrical cover 8 integral therewith, which is molded from a suitable insulator, preferably a flame-retardant synthetic resin. The annular cover 7 has an abutting end 15', a peripheral wall 15 that becomes annular by abutting the abutting ends 15', and a pair of semi-annular covers 7.
It consists of a and 7b. In addition, a bendable hinge portion 9 is provided at the portion of the peripheral wall 15 facing the abutting end 15'.
is formed (see Figure 3). The abutting end 15' and the peripheral wall 1 of the hinge part 9
5, semi-annular covers 7a and 7 are provided on the upper edge of each
b is formed into an inward brim shape. A stepped portion 10 (see FIG. 4) is formed along the inner peripheral edge of the lower surface of each semi-annular cover 7a, 7b, thereby forming an inner peripheral edge portion 11 that is thinner. Furthermore, tongue pieces 12 are formed at two locations on the inner peripheral edge 11 at appropriate intervals. Furthermore, by providing a radial step 13 (see FIG. 3) on the upper surface of the end of one semi-annular cover 7a, a superimposed part 14a which is made thinner is formed, and the end of the other semi-annular cover 7b is By forming an overlapping portion 14b having the same thickness as the inner peripheral edge portion 11 (see FIG. 5) and overlapping both overlapping portions 14a and 14b,
The upper and lower surfaces are overlapped without any difference in level, forming the abutted end 15' described above. Furthermore, front hanging portions 16a and 16b extending downward from the bushing 1 are formed at the end portion of the abutting end 15' side of the aforementioned peripheral wall 15. Each front hanging part 16
a, 16b have U-shaped sides 17a, 17b facing each other on both sides of the abutting end 15' (see FIG. 4), and a half tube forming the cylindrical cover 8 is formed on the sides 17a, 17b. Shape covers 8a and 8b are provided. Each of the half-cylindrical covers 8a and 8b has a U-shaped cross section (see FIG. 6), and when they are butted together, the electric wire 32 as a whole (see FIG. 10) is formed.
A square cylindrical cover 8 is formed which extends along the cylindrical shape and has a slight taper as a whole. Abutment pieces 18, 19 are formed on the upper and lower surfaces of one half-split cylindrical cover 8a, and each abutment piece 18, 19
Engagement holes 20, 21 (see Fig. 5) are provided in the holder. Further, overlapping pieces 22 and 23 are provided to protrude from each of the abutting pieces 18 and 19 toward the other half-cylindrical cover 8b. The other half-tubular cover 8b also has abutting pieces 24, 25 on the upper and lower surfaces, and each abutting piece 24, 2
5 are provided with engagement holes 26 and 27, and the engagement holes 2
0.21 so that it will fit tightly. Also, a stepped portion 2 for receiving the overlapping pieces 22 and 23 is provided.
8, 29 are provided, and both half-split cylindrical covers 8a, 8
When b are butted against each other, the overlapping pieces 22, 23 and the stepped portions 28, 29 overlap without any difference in level. Furthermore, three sideways projecting pieces 30, 31 are formed at the ends of each of the half-tubular covers 8a, 8b. Each of the protrusions 30, 31 is formed relatively thin and has the flexibility to be freely bent, and when the two half-tubular covers 8a, 8b are butted against each other, the left and right protrusions 30, 31 are at their tips. The lengths are such that they overlap slightly (see Figure 2). Although the protrusions 30 and 31 described above are formed horizontally, they may also be formed vertically as shown in FIG. Alternatively, as shown in FIGS. 8 and 9, linear protrusions 30 and 31 may be densely planted. However, in any case, these protrusions 3
0 and 31 are formed at positions with a required creepage distance from the live part in the recess 2. Note that the protrusions 30 and 31 only need to be long enough to contact the electric wire 32, so the protrusions 30 and 31 on the left and right do not necessarily have to be long enough to contact the electric wire 32.
It does not require a length such that 0 and 31 overlap. The above cap cover is as shown in Figure 10.
Around the bushing 1 with the electric wire 32 connected, wide open left and right (see Fig. 3),
The peripheral wall 15 is attached to the outer periphery of the upper end of the bushing 1, and the recess 2 between the upper end of the bushing 1 and the knob 6 is covered with each half-annular cover 7a, 7b, and each half-cylindrical cover 8a is placed around the electric wire 32. ,8
b, align the left and right butt pieces 18, 24 and 19, 25, and align the engaging pieces 26, 27.
are tightly fitted into the engagement holes 20 and 21 and integrated. When attached in this manner, each tongue piece 12 of the annular cover 7 is pressed against the base 6a of the knob 6 in a slightly curved manner. Although the direction of bending is shown upward in FIG. 10, it may be bent downward depending on the conditions at the time of installation. There are currently several types of shapes of the knob 6, but since the tongue piece 12 can be freely bent and the peripheral edge 11 can also be deformed in some cases, it can be applied to various types. On the other hand, each of the projecting pieces 30 and 31 of the cylindrical cover 8 is pressed against the electric wire 32. Since each protruding piece 30, 31 is flexible, it allows the electric wire 32 to freely vibrate or swing. Therefore, although stress concentration does not occur in the electric wire 32, a slight supporting force is exerted, which has the effect of alleviating the stress concentration in the portion of the electric wire 32 connected to the terminal 3. The degree of relaxation effect provided by each of the protrusions 30 and 31 was confirmed through experiments, and will be described as Experimental Example 1. Furthermore, it is generally necessary to avoid as much as possible the attachment of a bushing cap from affecting the characteristics of the bushing, particularly the flashover voltage characteristics. Therefore, since the above-mentioned example was confirmed through an experiment of the flashover voltage characteristics, this will be explained as Experimental Example 2. [Experiment Example 1] At the terminal of leadless stud type bushing,
A PDC wire (cross-linked polyethylene wire for high-voltage pull-down) with a length of 500 mm and a diameter of 2.5 mm was connected, and vertical and horizontal vibrations with a maximum amplitude of 26 mm were applied at 3100 times per minute. Measurements were made for the case without the cap and the case with the cap of the above embodiment of this invention. Table 1 shows the average values of the results measured for three samples (PDC lines).

[Experiment example 2]

In the experimental apparatus shown in FIG. 12, a voltage is applied between the transformer outer box 50 and the electric wire 32,
The tip of the cover plate 51 was defined as point A, the tip of the cylindrical cover 8 was defined as point B, and the terminal 3 was defined as point C, and the flashover voltage between these points was measured in the dry state and in the water-filled state. The average values of the results are shown in Table 2.

[Effect of idea]

Since this invention is as described above, it has the following effects. The annular cover 7 can cover the recess 2 present at the upper end of the bushing 1 without any gaps. Since the plurality of tongues 12 formed on the inner circumferential edge of the annular cover 7 contact the base 6a of the knob 6 and curve, the degree of curvature of the tongues 12 will vary even if the diameter and shape of the base 6a differ. This allows the difference to be absorbed and the center of the bushing cap 1 to be maintained at all times. Even if there is a size difference between the outer diameter of the upper end of the bushing 1 and the inner diameter of the peripheral wall 15 and a gap exists between the two, the tongue piece 12
Since it is in pressure contact with the base 6a, it is stably supported by the base 6a while being aligned with the center of the base 6a. A front hanging portion 16a is provided on the peripheral wall 15 of the annular cover 7.
16b, and its front hanging parts 16a, 16b
Since the cylindrical cover 8 is formed at
can be covered, and the notch 5 can be closed within the size range of the front hanging parts 16a and 16b. Since the cylindrical cover 8 is provided, even if there is variation in the exposed length of the conductor of the electric wire, the distance from the conductor to the ground fault part can be kept at least by the length of the cylindrical cover 8. In addition, since there is no part that comes into contact with a live part such as the terminal 3, the flashover voltage characteristics of the bushing are not deteriorated. Since a plurality of flexible protrusions 30 and 31 are formed on the inner surface of the tip of the cylindrical cover 8, it is possible to alleviate stress concentration when the electric wire vibrates, and to extend the life of the electric wire.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the bushing, Figure 2 is a perspective view of the embodiment, Figure 3 is a perspective view of the open state, Figures 4 and 5 are perspective views from a different perspective, and Figure 6 is a perspective view of the bushing. A sectional view taken along the - line in Figure 2, Figures 7 and 8.
The figure is a front view of another embodiment, and FIG. 9 is the − of FIG. 8.
10 is a perspective view of the device in use, FIG. 11 is a cross-sectional plan view of the conventional example, and FIG. 12 is a front view of the experimental device. 1... Bushing, 2... Recess, 3... Terminal,
4... Electric wire insertion hole, 5... Notch, 6... Knob, 6a... Base, 7... Annular cover, 7a, 7
b... Semi-annular cover, 8... Cylindrical cover, 8a,
8b...Half-split cylindrical cover, 9...Hinge part, 10
... Stepped portion, 11 ... Inner peripheral edge, 12 ... Tongue piece, 1
3...Step part, 14a, 14b...Polymerization part, 15...
...Peripheral wall, 15'...Butting end, 16a, 16b
...Front hanging part, 17a, 17b...Side side, 18,
19... Butt piece, 20, 21... Engagement hole, 2
2, 23... Overlapping piece, 24, 25... Butting piece, 26, 27... Engaging piece, 28, 29... Step portion, 30, 31... Projecting piece, 32... Electric wire, 40...
... Cover, 41 ... Cylindrical cover, 42 ... Arm, 43 ... Butt portion, 44 ... Opening portion, 5
0...Transformer outer box, 51...Cover plate.

Claims (1)

[Claims for Utility Model Registration] A terminal 3 having a wire insertion hole 4 is protruded from the center of the tip recess 2, a wire holding knob 6 is attached to the terminal 3, and a cutout 5 for wire insertion is attached to the peripheral wall of the recess 2. In the bushing cap attached to the bushing 1 for the primary terminal of a pole-mounted transformer, the annular cover 7 covers the upper end of the bushing 1.
A butting end 15' is provided in a part of the annular cover 7, and the annular cover 7 is composed of a peripheral wall 15 which becomes annular by abutting the abutting ends 15', and a pair of semi-annular covers 7a and 7b. A bendable hinge portion 9 is formed in a portion of the peripheral wall 15 facing the abutting end 15', and the abutting end 1
The above-mentioned semi-annular covers 7a, 7b are formed on the upper end edge of the peripheral wall 15 between 5' and the hinge part 9, and a plurality of tongue pieces 12 are formed on the inner peripheral edge of each semi-annular cover 7a, 7b. Front hanging parts 16a, 16b extending downward along the outer peripheral surface of the bushing 1 are formed at the ends on the butting end 15' side, and a cylindrical cover 8 is formed on the front hanging parts 16a, 16b.
The half-split cylindrical covers 8a and 8b constituting the cylindrical covers 8a and 8b are integrally formed, and an engaging piece 2 is provided on one side of each half-split cylindrical cover 8a and 8b.
6, 27, and the engagement hole 20, 2 facing this on the other side
1, and a plurality of flexible protrusions 30, 31 are formed on the inner surface of the tip end of each of the half-split cylindrical covers 8a, 8b in contact with electric wires.