JPH0534193Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an improvement of an insulating molded body for a cable connection portion.

<Prior art> When connecting a plastic power cable such as a cross-linked polyethylene power cable, as a prefabricated construction method to simplify the work, as shown in FIG. ′
An insulating cylindrical body 2' made of epoxy resin in which an electrode 1' is embedded is placed in the center of the inner surface of the electrode,
The respective stress cones 4', 4' fixed on the conductor connection fittings 3' of the cables and passed through each cable in advance are pulled back to the stress cone receiving holes 21', 21 inside both ends of the insulating cylinder 2'. ' is compressed by a spring member (not shown), and the insulating cylindrical body 2' is compressed by a spring member (not shown).
It is known to make a connection between each end of the cable and the sheath of each cable by an auxiliary jacket connection tube (not shown).

<Problem to be solved by the invention> In the above-mentioned insulating cylinder with embedded electrodes, when the epoxy resin is heated and cured, due to the difference in thermal expansion coefficient between the epoxy resin and the electrode material, the electrode and the epoxy resin Thermal stress is generated at the contact interface with the resin, and this thermal stress becomes residual stress. During cable operation, this residual stress is superimposed on the thermal stress due to the cable and heat cycle, so interface peeling occurs at locations where residual stress is excessive. is likely to occur.

Of the interface between the electrode and the epoxy resin in the insulating cylinder shown in Figure 2, the epoxy resin part that contacts the tip of the shielding ring is the part where the distribution of thermal stress is the most complex among the interfaces where electrical stress acts. Therefore, it is easy to become the starting point of dielectric breakdown due to the above-mentioned interfacial peeling.

Therefore, it is desirable to alleviate the thermal stress at the tip of the shielding ring.

Therefore, in the insulating cylinder shown in Fig. 2, if the thickness of the shielding ring can be made sufficiently thin, the shielding ring will not be bent by the thermal stress acting on the tip of the shielding ring when the epoxy resin is thermally cured. However, there is a limit to making the shield ring thinner in the insulating cylinder as described above due to the attachment of the shield ring to the metal fittings. Effective absorption of thermal stress at the tip of the shield ring cannot be expected due to thinning of the wall (copper is normally used for the electrode material, and when welding is used to attach the shield ring, the thickness of the shield ring may be reduced by groove processing). In addition, it is necessary to make the shielding ring fairly thick so that the entire thickness of the shielding ring at the welding point does not melt.For example, when soldering, even if the shielding ring can be made thinner, it is difficult to maintain a stable installation condition. (difficult to guarantee gender).

In view of the above points, an object of the present invention is to provide an insulating molded body for a cable connection part that can effectively prevent dielectric breakdown caused by thermal stress at the end of an electrode.

<Means for Solving the Problems> The insulating molded body for a cable connection part of the present invention is an insulator in which a cylindrical electrode is embedded in a cylindrical resin molded body. An annular groove adjacent to each end of the cylindrical electrode is machined, and this annular groove portion is made to resist thermal stress generated due to the difference in thermal expansion between the resin molded product and the cylindrical electrode during molding of the insulator. This structure is characterized by a thin wall that allows it to bend.

<Explanation of Examples> The present invention will be explained below with reference to the drawings.

In FIG. 1, 1 is a cylindrical electrode, each end 11, 11 is processed into a curved surface to relieve electrical stress, and a protrusion 12 is provided at the center of the inner surface. Reference numerals 13 and 13 denote annular grooves formed on the inner circumferential surface of the cylindrical electrode adjacent to each of the ends, and thin portions 131 and 131 exist because of these annular grooves. 2 is an epoxy resin molded product, which surrounds the outer peripheral surface and both ends of the electrode 1, and has annular grooves 13, 13.
The inside is filled. 21, 21 are stress cone receiving holes provided inside both ends of the molded product 2.

The above epoxy resin molded product 2 is molded by casting, and in this case, when the heated molded product and cylindrical electrode are cooled to room temperature, the difference in thermal expansion coefficient between the epoxy resin and the electrode material (copper) (The epoxy resin is larger) Therefore, the thermal stress during the cable heat cycle is superimposed on the residual stress due to this thermal stress, and the areas where interfacial peeling occurs and dielectric breakdown is likely to occur are between the ends of the electrode and the epoxy resin. As described above, it is the interface with the resin.

However, in order to understand the thermal stress distribution state on the curved surface of the electrode end 11, it is necessary to
0 and 20 press the electrode 1 between them from both sides,
The stress generated at the interface between the curved surface of both electrode ends 11 and the epoxy resin in response to this pressing external force F can be assumed.

In the insulating molded article for a cable connection part of the present invention, in the insulator in which a cylindrical electrode is embedded in a cylindrical resin molded article, each end of the cylindrical electrode is attached to the inner peripheral surface of the cylindrical electrode. Adjacent annular grooves are machined to make the bottom of the annular groove thinner, allowing the electrode to be constructed from a single material.
Unlike the conventional example shown in Fig. 2, there is no need to join separate members (metal fittings and shielding ring), and thin-walled parts can be made sufficiently thin without welding restrictions. Since the thin-walled portion can be easily bent by pressing, the thermal stress acting on the interface of each end 11 of the electrode can be alleviated, and dielectric breakdown starting at each end of the electrode due to thermal stress during molding can be prevented. It can be prevented.

In addition, unlike the case where separate components are joined by soldering, such joints can be eliminated and the support state of thin-walled parts can be maintained extremely stably, so that the joint can withstand repeated thermal stress caused by cable heat cycles. It is possible to avoid dielectric breakdown caused by damage to parts.

The thickness of the thin portion is 1/5 or less, preferably 1/7 to 1/10, of the electrode thickness (the electrode thickness at the location before forming the annular groove).

The insulating molded body for cable connection parts according to the present invention is
Usually used for 154KV or 275K, the dimensions for 275KV are: Length of resin molding: 920mm, Outer diameter of the molding: 380mm, Length of electrode: 410mm, Outer diameter of electrode: 248mm, Inner diameter of electrode 140mm, thickness of thin part: 3mm, width of groove: 20mm. When this example product for 275KV was subjected to a submerged heat shock test, no decrease in voltage resistance was observed, but a decrease in voltage resistance was observed for the conventional product that did not form a thin wall portion.

<Effects of the invention> The insulating molded body for cable connection parts of the present invention has the configuration as described above, and prevents dielectric breakdown caused by residual thermal stress in the epoxy resin portion that contacts each end of the cylindrical electrode from the cable of the electrode. It is possible to provide an insulating molded body for a cable connection part that maintains mechanical stability well under heat cycles, can sufficiently prevent heat cycles, and has excellent voltage resistance.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing an insulating molded body for a cable connection part according to the present invention, and FIG. 2 is an explanatory view showing a known prefabricated cable connection part. In the figure, 1 is a cylindrical electrode, 13, 13 are annular grooves, 131, 131 are thin parts, and 2 is a cylindrical resin molded product.

Claims (1)

[Scope of utility model registration request] In an insulator in which a cylindrical electrode is embedded in a cylindrical resin molding, an annular groove is machined on the inner peripheral surface of the cylindrical electrode to be adjacent to each end of the cylindrical electrode, and the annular groove portion is An insulating molded body for a cable connection portion, characterized in that the insulating molded body is made thin so as to be able to bend against thermal stress generated due to a difference in thermal expansion between the resin molded product and the cylindrical electrode during molding of the insulator.