JP2013229312A - Porcelain tube for bushing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porcelain tube for a bushing capable of improving withstand voltage characteristics without thickening the porcelain tube itself.SOLUTION: This porcelain tube for the bushing includes a double-level shade composed of a large diameter shade 1 and a small diameter shade 2, and a bulged portion 4 is formed at the tip of the large diameter shade 1. When the thickness of the vertical section of the bulged portion 4 is set as T, and the minimum thickness of the tip part of the shade is set as t, t/T=0.6-0.8, and the curvature radius R of the vertical section is within a range of 5.5-11 mm. Thereby, a potential gradient at the tip part of the shade is lowered in comparison with a conventional one, and voltage withstand characteristics against generation of corona and impulse overvoltage can be improved.

Description

  The present invention relates to a bushing soot tube, and more particularly to a bushing soot tube suitable for a high voltage bushing of 550 kV or higher.

  The bushing has a central conductor penetrating through the inner center of the bushing bush, and an electric field is generated around it by a high-voltage current flowing through the central conductor. In particular, the electric field distribution on the surface of the soot tube is an important factor affecting the external insulation performance. If the surface field distribution on the surface of the soot tube is inadequate, a flashing caused by an overvoltage such as a lightning impulse or a switching impulse, or when an operating voltage is applied Problems such as the generation of corona in the air occur.

  Thus, conventionally, for example, as disclosed in Patent Document 1, a device has been devised to control an electric field by forming a capacitor core or arranging an electrode around a central conductor to improve insulation performance. However, the effect of the bushing for high voltage of 550 kV or higher, especially the bushing for ultra-high voltage of 1000 kV or higher has reached its limit. By unavoidably increasing the thickness of the bushing for bushing itself, It is decreasing. However, the thickening of the bushing bushing leads to an increase in the size and weight of the equipment and a problem that the manufacturing cost increases.

JP 2010-192277 A

  Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to provide a bushing bush that can improve the withstand voltage characteristic without increasing the thickness of the rod itself.

  As a result of repeated studies to solve the above problems, the present inventor can relax the electric field distribution on the surface of the soot tube that influences the external insulation performance by devising the shape of the tip of the shade, which increases the size of the device. It has been found that it is possible to improve the withstand voltage characteristics without increasing the diameter of the connecting barrel body and the shade.

  The present invention has been completed on the basis of the above-mentioned knowledge, and is a bushing bushing provided with a stepped shade made of a large diameter shade and a small diameter shade, comprising a bulging portion at the tip of the large diameter shade, When the thickness of the bulging portion in the vertical cross section is T and the minimum thickness of the cap tip is t, t / T is in the range of 0.6 to 0.8, and the radius of curvature R in the vertical cross section is It exists in the range of 5.5-11 mm. In addition, the vertical cross section said here refers to the vertical cross section which passes along the central axis line of a soot pipe. The wall thickness T is in contact with the arc tangent at the point where the cross-sectional line of the upper surface of the cap portion intersects with the arc of the cross-section of the tip bulge, and is parallel to the tangent and below the arc of the cross-section of the bulge. It shall be defined by the distance between the lines.

  In addition, as in claim 2, the vertical cross-sectional shape on the tip side of the bulging portion is a structure formed by an arc having a single radius of curvature with a radius of curvature R of 5.5 to 11 mm. The vertical cross-sectional shape on the distal end side of the protruding portion can be a structure composed of upper and lower arcs having a radius of curvature R of 5.5 to 11 mm and a common tangent line. In any case, when the diameter of the large diameter shade is D and the diameter of the small diameter shade is d, it is preferable that D / d = 1.1 to 1.8.

  In the bushing bush for the bushing according to the present invention, the electric field strength along the surface of the steel pipe can be reduced as compared with the conventional product by forming the above-mentioned bulged portion at the tip of the large-diameter shade where the electric field strength is the largest. For this reason, it is possible to not only suppress the corona discharge in the air when operating voltage is applied, but also improve the insulation performance against overvoltage such as lightning impulse and switching impulse, without increasing the diameter of the pipe tube and shade. Can do.

It is sectional drawing which shows the shade shape of the conventional bushing soot pipe. It is sectional drawing which shows the shade shape of the bush pipe for bushings of the 1st Embodiment of this invention. It is sectional drawing which shows the shade shape of the bush pipe for bushings of the 2nd Embodiment of this invention. It is an equipotential diagram at the time of using the bush for bushing of this invention.

Preferred embodiments of the present invention are shown below.
FIG. 1 is a sectional view showing a shade shape formed on the outer peripheral surface of a conventional bushing soot tube, and shows three types of shades 1, 2 and 3 having different shade diameters. Reference numeral 1 denotes a large-diameter shade and 2 denotes a small-diameter shade smaller than the large-diameter shade 1. These large-diameter shades 1 and the small-diameter shade 2 are combined at a predetermined pitch to form a stepped shade. When the diameter of the large-diameter shade is D and the diameter of the small-diameter shade is d, it is preferable that D / d = 1.1 to 1.8. Reference numeral 3 denotes a maximum diameter shade called a water drainage shade, which is arranged at intervals of about 1 m in order to prevent washing water and rainwater from flowing along the surfaces of the large diameter shade 1 and the small diameter shade 2. Is normal.

  When 1200 kV is applied to the center conductor of such a conventional bushing soot tube, the dielectric constant of air is 1.0 while the dielectric constant of the porcelain constituting the soot tube is 6.8. The electric field on the air side becomes high at the tip of the. In the case of FIG. 1, the potential gradient at the tip of the large-diameter shade 1 is 2.15 kV / mm, and the potential gradient at the tip of the small-diameter shade 2 is 1.75 kV / mm. It has reached .15 kV / mm.

  Therefore, in the present invention, as shown in FIGS. 2 and 3, the bulging portion 4 is formed at the tip of the large-diameter shade 1 among the uneven shades, thereby reducing the potential gradient at the tip of the large-diameter shade 1. In FIG. 4 to be described later, a bulging portion 5 is also formed at the tip of the water drainage shade 3. In the case of installing the water drainage shade, the shape thereof needs to be similar to the tip shape of the large diameter shade 1. Even if the radius of curvature increases, the number of sheets is small, so there is little adverse effect on cost.

  FIG. 2 is a vertical sectional view showing the first embodiment of the bulging portion 4, in which the vertical sectional shape on the distal end side of the bulging portion 4 is an arc having a single curvature radius. When the thickness in the vertical section of the bulging portion 4 is T and the minimum thickness at the tip of the shade is t, the radius of curvature R in the vertical section is t / T = 0.6 to 0.8. It shall be in the range of 5.5-11 mm. In the case of FIG. 2, T is twice the radius of curvature R.

  Here, if the value of t / T exceeds 0.8, it leads to an increase in cost, which is not preferable. Conversely, if the value of t / T is less than 0.6, the bulging portion 4 is relatively large, which increases the difficulty of the manufacturing process such as molding, drying, and firing, leading to an increase in manufacturing cost. Absent.

  Further, if the radius of curvature R in the vertical cross section is less than 5.5 mm, it approaches a conventional shade and the potential gradient relaxation effect is reduced. Conversely, if the radius of curvature R exceeds 11 mm, it will lead to an increase in manufacturing cost, which is not preferable.

  FIG. 3 is a vertical cross-sectional view showing a second embodiment of the bulging portion 4, in which the vertical cross-sectional shape on the tip side of the bulging portion 4 is composed of upper and lower arcs and their common tangent lines. Here, the curvature radii R of the upper and lower arcs may be the same or different, but for the reasons described above, the curvature radius R of the upper and lower arcs is in the range of 5.5 to 11 mm. Moreover, t / T shall be in the range of 0.6-0.8.

In the embodiment, T is 22 mm. For this reason, when the curvature radii R of the upper and lower arcs are both 5.5 mm, the length of the common tangent (straight portion) is 11 mm, but common when the curvature radii R of the upper and lower arcs are both 11 mm. The length of the tangent (straight part) is zero. Thus, the length of the common tangent changes according to the curvature radius R of the upper and lower arcs.
Next, the basis of the present invention is shown by specific data.

  Table 1 shows the potential gradient of the porcelain surface at the tip of the shade when 1200 kV is applied to an ultrahigh voltage bushing having various shade shapes with different parameters. However, all are data in the case where a bulging portion is also provided at the tip of the water drainage shade 3. Since the conventional products 1 and 2 have a t / T of 1.0, they have a shade shape with no bulge, and the potential gradient exceeds 1.8. Inventive products 1 to 10 have a potential gradient of 1.75 or less.

  The present invention products 1 and 2 and the present invention products 6 and 7 have the single curvature radius (R) shown in FIG. Inventive product 2 having a larger R than invented product 1 has a lower potential gradient. In addition, when the curvature radii are the same, the potential gradient is further reduced in the products 6 and 7 of the present invention having a large overhang of the large diameter cap. In the products 3, 4 and 8, 9 of the present invention, the tip of the shade consists of the upper and lower arcs shown in FIG. 3 and the common tangent line. Since the protrusions of the large-diameter shades are larger in the case of 8 and 9 than the products 3 and 4 of the present invention, the potential gradient is lowered. The product 5 of the present invention has an upper curvature radius of 11 mm and a lower curvature radius of 8 mm. In this embodiment, the common tangent line of the products 3 and 4 of the present invention is substantially parallel to the central axis of the soot tube, but the inclination of the common tangent line is not limited to this, and is inclined with respect to the central axis of the soot tube. There is no problem.

  FIG. 4 is an equipotential diagram when 1200 kV is applied to the ultra high voltage bushing employing the bushing bushing of the present invention. As shown in the figure, the electric field becomes high at the tip of the large-diameter shade 1 and is mitigated at the tip of the small-diameter shade 2 inside. Therefore, if only the tip shape of the large-diameter shade 1 is devised, a practical withstand voltage is obtained. An improvement effect can be obtained.

  The bush for bushing of the present invention can be used for both oil-immersed paper bushing and gas bushing. In particular, in the voltage class of 550 kV or more, the effect is large because the electric field on the surface of the soot tube becomes high.

  In addition to suppressing airborne corona when operating voltage is applied, it is possible to improve insulation characteristics against overvoltage. When an impulse overvoltage is applied, streamers are generated from metal parts such as the charge side, ground side metal fittings, and shields, and there is a tendency for flashing, but during rainfall, corona discharge occurs at a low voltage due to the influence of water droplets along the side of the tub. May start. This phenomenon indicates that the electric field along the side of the soot pipe influences the insulation performance, and it is possible to improve the insulation characteristics by applying the present invention.

1 Large diameter shade 2 Small diameter shade 3 Water drainage shade

Claims (4)

  A bushing for a bushing having a stepped cap made up of a large-diameter cap and a small-diameter cap, having a bulging portion at the tip of the large-diameter cap, and having a wall thickness T in the vertical section of the bulging portion, For the bushing, wherein t / T = 0.6 to 0.8 and the radius of curvature R in the vertical cross section is in the range of 5.5 to 11 mm, where t is the minimum wall thickness.碍 管.   2. The bushing for a bushing according to claim 1, wherein the bulging portion has a vertical cross-sectional shape of a circular arc having a single curvature radius with a curvature radius R of 5.5 to 11 mm.   The bushing scissors according to claim 1, wherein the bulging portion has a vertical cross-sectional shape formed by upper and lower arcs having a curvature radius R of 5.5 to 11 mm and a common tangent line.   2. The bushing bushing according to claim 1, wherein D / d = 1.1 to 1.8, where D is the diameter of the large-diameter shade and D is the diameter of the small-diameter shade.

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