JP2017162551A - Earthquake resistant polymer bushing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an earthquake resistant polymer bushing having enhanced vibration attenuation factor.SOLUTION: The earthquake resistant polymer bushing generates earthquake-proof effects by arranging a center tube 4 in a center part of a polymer porcelain tube 1, hanging a plastic conductor 5 inside of the center tube 4 and vibrating the plastic conductor 5 inside of the center tube 4 when earthquake is generated. Space δ between the plastic conductor 5 and an inner wall of the center tube 4 is about 5 to 20 mm. A lower part of the plastic conductor 5 may be fixed to the center tube 4 or hung without fixing.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a polymer bushing excellent in earthquake resistance.

  In the 2011 off the Pacific coast of Tohoku Earthquake, many electrical facilities were damaged. In particular, in the old type air-oil bushing used for the main transformer, which is the key to power distribution, there were some cases in which porcelain destruction and continuous oil leakage occurred due to earthquake motion more than expected, leading to supply failure. .

  Recent porcelain bushings have improved porcelain strength and improved oil-tight packing, and it has been confirmed that similar damage will not occur at the above-mentioned earthquake level. One example thereof is described in Patent Document 1. However, cost reduction of power distribution facilities and further seismic strengthening that can withstand earthquakes with a seismic intensity of 6 or higher that are expected to occur within the next 30 years are required, and many old transformers installed during the high growth period have been renewed. At times, bushings that apply new technologies are required.

  Compared to porcelain bushings, polymer bushings are lightweight and are considered advantageous in terms of earthquake resistance. However, since the polymer is less rigid than the porcelain and the vibration resistance of each component joint is low, there is a drawback that the vibration is difficult to attenuate and the response magnification becomes high, which is disadvantageous in terms of earthquake resistance.

  Here, the response magnification means a multiple of the product center-of-gravity point acceleration with respect to the ground surface acceleration during vibration. The graph of FIG. 1 shows the relationship between the vibration attenuation rate h and the response magnification, and shows that the response magnification increases as the vibration attenuation rate h decreases.

  As described above, the polymer bushing has an advantage that it is lightweight, but on the other hand, since the vibration damping rate is smaller than that of the porcelain bushing, there is a drawback that the response magnification at the time of occurrence of an earthquake is increased.

JP-A-5-47569

  Accordingly, an object of the present invention is to provide an earthquake-resistant polymer bushing having an improved vibration damping rate by solving the above-mentioned conventional problems.

  The earthquake-resistant polymer bushing of the present invention, which has been made to solve the above-mentioned problems, has a central tube disposed in the center of a polymer pipe, and a flexible conductor is suspended inside the central tube. The vibration control effect is produced by swinging the inside of the central tube.

  In addition, it is preferable to set it as the structure which gave the space | gap of 5-20 mm on one side between the said flexible conductor and the inner wall of a center pipe | tube. The lower portion of the flexible conductor can be a structure fixed to the central tube, or a structure suspended without being fixed to the central tube. The central tube can be an aluminum tube, and the flexible conductor can be made of a copper stranded wire having good current-carrying performance.

  The earthquake-resistant polymer bushing according to the present invention has a flexible conductor suspended inside a central tube arranged at the center of the polymer rod, and causes the flexible conductor to swing inside the central tube when an earthquake occurs. Therefore, it is possible to produce a vibration control effect. For this reason, the vibration damping rate of the entire polymer insulation pipe is increased, and the earthquake resistance can be improved.

It is a graph of the acceleration response magnification at the time of sine n-wave quasi-resonance, and h is a vibration damping factor. It is a fragmentary sectional view which shows the earthquake-resistant polymer bushing of embodiment. It is a horizontal sectional view of a center conductor. It is explanatory drawing which shows the periodic motion of the flexible conductor inside a center pipe | tube. It is a graph which shows the relationship between the space | gap (delta) and acceleration. It is a graph of a bushing base moment.

Embodiments of the present invention will be described below.
FIG. 2 is a partial cross-sectional view showing an earthquake-resistant polymer bushing according to an embodiment of the present invention. The polymer pipe 1 is generally formed by molding silicon rubber on the outer periphery of an insulating tube 3 made of FRP, and the inside thereof is filled with an insulating gas such as SF ₆ gas or nitrogen gas.

  The center conductor of the earthquake-resistant polymer bushing of the present invention comprises a center tube 4 disposed at the center of the polymer rod tube 1 and a flexible conductor 5 suspended therein. FIG. 3 shows a horizontal sectional view thereof. Reference numeral 6 denotes a capacitor core for electric field relaxation formed on the outer periphery of the central tube 4. Another embodiment of the present invention is a polymer bushing (gas bushing) that does not have a capacitor core for electrolytic relaxation.

  In the present embodiment, the center tube 4 is made of an aluminum tube. As a general central conductor of the bushing, a copper tube or an aluminum tube having a high conductivity is used. The aluminum tube is light, but the conductivity is about 60% of that of the copper tube. However, since current flows through the flexible conductor 5 in the present invention, there is no problem even if an aluminum tube having a lower conductivity than the copper tube is used as the center tube 4.

  The outer diameter Φa of the central tube 4 is set so that the electric field strength on the surface thereof is equal to or lower than the dielectric breakdown voltage (μ−3δ) of the insulating gas sealed in the bushing. That is, since the electric field strength of the surface increases as the radius of curvature of the central tube 4 decreases, the outer diameter Φa of the central tube 3 is preferably about 60 to 100 mm in the 154 kV or 275 kV voltage class bushings.

  The flexible conductor 5 is preferably made of a copper stranded wire having excellent conductivity. Since the flexible conductor 5 has fine irregularities on the surface, it cannot be used in a place with a high electric field. However, in the present invention, since the flexible conductor 5 is arranged inside the metal central tube 4, it is shielded and discharge due to the irregularities on the surface is prevented. It is not.

  The cross-sectional area of the flexible conductor 5 is set according to the current carrying capacity, and its outer diameter Φb is determined. That is, the outer diameter Φb of the flexible conductor 5 is determined so that the temperature rise due to the energization heat generation is not more than the allowable temperature of the electric wire.

  In the present invention, since it is necessary to swing the flexible conductor 5 inside the center tube 4, it is necessary to have a gap δ between the flexible conductor 5 and the inner wall of the center tube 4. If the gap δ is too small, the swing of the flexible conductor 4 becomes insufficient. On the other hand, if the gap δ is too large, the diameter of the central tube 3 must be increased, which increases the diameter of the bushing and increases the cost. A preferable range of the gap δ will be described later.

  Note that the lower portion of the flexible conductor 5 may be fixed to the central tube 4 or may be suspended from the central tube 4 without being fixed. However, in order to enhance the vibration control effect described below, it is preferable to fix to the central tube 4. Although the flexible conductor 5 is tensioned by its own weight, it is not preferable to apply a strong external tension. This is because, if a strong external tension is applied, the swinging of the flexible conductor 5 is hindered and the vibration control effect described below cannot be obtained.

  The earthquake-resistant polymer bushing of the present invention configured as described above swings when an earthquake occurs, and particularly vibrates greatly when resonating with an earthquake wave. However, since the flexible conductor 5 is flexible, it swings inside the central tube 4 later than the central tube 4. As a result, as shown in the horizontal sectional view of FIG. 4, the flexible conductors 5 are alternately pressed against the inner surfaces on both sides of the central tube 4. At this time, the product of the mass of the flexible conductor 5 and the reversal acceleration acts on the central tube 4 to exert a vibration control effect. In the 154 kV class bushing, the maximum amplitude is about 20 mm. Therefore, the air gap δ should be set to a realistic value in consideration of this value as described below.

  From the natural frequency of the bushing of the voltage class of 154 kV or 275 kV, assuming that the flexible conductor 5 moves inside the central tube 4 at 10 Hz, the gap δ and the acceleration of the flexible conductor 5 are shown in FIG. There is a relationship to show.

  According to the JEAG standard for a polymer bushing of 154 kV, the acceleration of the center of gravity of the polymer bushing is about 2 G and an oscillation force of about 2000 N · G due to the mass effect when an earthquake occurs. Therefore, a braking force of about 200 N · G is required to improve the seismic performance of the polymer bushing by 10%.

  On the other hand, the weight of the flexible conductor 5 is about 30 N / m, and the air-side dimension of the polymer bushing of 154 kV is about 2 m. Therefore, the weight of the flexible conductor 5 is 60 N, and acceleration of 120 N · G and 5 G at 2 G acceleration. The braking force is 300 N · G. Therefore, in order to obtain a braking force of about 200 N · G, the flexible conductor 5 may be pressed against the inner wall of the central tube 4 with an acceleration of 3.3 G. For this purpose, the gap δ may be about 8 mm from the graph of FIG.

  If the gap δ is enlarged, the acceleration increases and the braking force increases. However, it is necessary to increase the diameter of the half-surface center tube 4, which causes an increase in the size of the bushing. Therefore, in practice, the gap δ is preferably about 5 to 20 mm.

  As a result of such a vibration control effect by the flexible conductor 5, the vibration damping rate increases, the base moment of the bushing decreases as shown in the graph of FIG. 6, and the earthquake resistance is improved.

  As described above, the earthquake-resistant polymer bushing of the present invention is designed so that the central tube 4 and the flexible conductor 5 vibrate without being synchronized when an earthquake occurs. For this reason, there is an advantage that the vibration damping rate is increased by the damping force generated from the mass and acceleration of the flexible conductor 5 and the bending moment of the base of the bushing can be reduced.

DESCRIPTION OF SYMBOLS 1 Polymer soot pipe 2 Lower metal fittings 3 Insulation cylinder 4 Center pipe 5 Flexible conductor 6 Capacitor core

Claims (6)

  A central pipe is placed in the center of the polymer pipe, a flexible conductor is suspended inside the central pipe, and the flexible conductor is oscillated inside the central pipe in the event of an earthquake. An earthquake-resistant polymer bushing characterized by   The earthquake-resistant polymer bushing according to claim 1, wherein a gap of 5 to 20 mm on one side is provided between the flexible conductor and the inner wall of the central tube.   The earthquake-resistant polymer bushing according to claim 1 or 2, wherein a lower portion of the flexible conductor is fixed to a lowermost metal fitting.   The earthquake-resistant polymer bushing according to claim 1 or 2, wherein a lower portion of the flexible conductor is suspended without being fixed to a lowermost metal fitting.   The earthquake-resistant polymer bushing according to any one of claims 1 to 4, wherein the central tube is an aluminum tube.   The earthquake-resistant polymer bushing according to any one of claims 1 to 5, wherein the flexible conductor is a copper stranded wire.