JPH0323789Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a device for protecting a sheath of a power cable, and more particularly to a cable sheath protection device equipped with abnormality detection means.

(Technical background of the invention and its problems) Conventionally, a cable sheath protection device having a structure in which a nonlinear resistance element is used as a gear press arrester is known.

That is, for example, as shown in FIG. 3, a nonlinear resistance element 2 is housed in a ceramic case 1, and this element 2 is
A cable sheath protection device is known in which an electrode plate 4 having a terminal 3 on one side is connected via a spring 5, and another electrode plate 4 having a terminal 3 on the other side is brought into direct contact.

However, in a protective device with such a structure, the terminal 3,
When a high voltage is applied between the electrode plates 4 and 3, a short circuit occurs between the electrode plates 4, 4, and the sheath protection function cannot be reliably achieved. It also has the disadvantage of being unsuitable for locations that may be submerged in water.

Therefore, recently, as shown in Fig. 4, electrode terminals 6, 6 are fixed directly to both sides of the nonlinear resistance element 2 by soldering or with conductive adhesive, and these are integrally molded with epoxy resin or the like. It has also been done to form an insulator 7 by using the insulator 7 to cover part of the element 2 and the electrode terminals 6, 6, but when the insulator 7 is brought into direct contact with the element 2 in this way, Not only does the heat dissipation of the element 2 decrease, but also stress is applied to the element 2 due to expansion and contraction of the insulator 7, which is undesirable.

By the way, as a cable sheath protection device of this kind, as shown in FIG. There is known an abnormality detecting means having a structure in which the rod 10 protrudes and the tip of the rod 10 is fixed to one side of the element 2 by soldering 11. In this protection device, when the nonlinear resistance element 2 is destroyed by an abnormal voltage from the cable sheath, the element 2 generates heat due to the current caused by this abnormal voltage, and when the solder 11 melts, the abnormality indicator bar 10 is activated by the spring. 9 is used to detect the occurrence of abnormal voltage.

However, in a protective device with such a structure, if abnormal voltage is not continuously applied, the solder 1
Since No. 1 does not melt, it has the disadvantage that it is not possible to detect the occurrence of abnormal voltage.

(Purpose of the invention) An object of the invention is to provide a cable sheath protection device that does not apply stress to a nonlinear resistance element and can reliably detect the occurrence of an abnormal voltage.

(Summary of the invention) In this invention, a nonlinear resistance element is airtightly housed in a case covered with an insulator, and a pair of electrode terminals connected to the sheath terminal of an insulated junction box are directly connected to both sides of this element. At the same time, one electrode terminal is extended into the transparent pipe, a communication hole is provided in this electrode terminal to communicate the inside of the case and the transparent pipe, and this communication hole is hermetically closed on the transparent pipe side with a foil member. It is characterized by

(Embodiments of the invention) Hereinafter, embodiments of the invention will be described in detail with reference to the drawings.

FIG. 2 shows an insulated junction box 12, which includes both power cables 13, 13.
The cables 13, 13 are connected while separating and insulating each sheath (not shown) by an insulating tube (not shown). A pair of sheath terminals 15, 15 electrically connected to the sheath of each cable protrude from each anti-corrosion layer 14 of this insulated junction box 12, and a lead wire 15 is connected between these sheath terminals 15, 15.
6 through the cable sheath protection device 17 of the present invention
is connected.

Now, cable sheath protection device 1 according to the present invention
7 includes a case 18, as shown in FIG. This case 18 is made of glass fiber reinforced plastic (FRP), and the nonlinear resistance element 2 is housed inside. Electrode terminals 19 and 19' are directly fixed to both sides of this nonlinear resistance element 2 via a conductive adhesive. These electrode terminals 19 and 19' each protrude from the case 18 and are connected to the lead wire 16. A heat-shrinkable tube 20 is mounted on the case 18 so as to span both electrode terminals 19, 19', and an insulator 21 made of epoxy resin molded is provided on the heat-shrinkable tube. Thereby, the inside of the case 18 is kept airtight.

A protruding portion of one electrode terminal 19' from the case 18 extends into the transparent pipe 22. One end of the transparent pipe 22 is fitted into the insulator 21 on the electrode terminal 19', and is fixed by wrapping a waterproof tape 23 around it. One of the electrode terminals 19' is provided with a communication hole 24 that opens inside the case 18 and the transparent pipe 22 and communicates them. It is hermetically closed with foil 25.

Note that waterproof tape 23 is wound between the insulator 21 and the lead wire 16 and between the transparent pipe 22 and the other lead wire 16, respectively.

In this way, when the nonlinear resistance element 2 is housed in the case 18, the insulator 21 does not come into direct contact with the element 2, so even if the insulator 21 repeatedly expands and contracts, no stress is applied to the element 2. There is no.

In addition, a surge enters the conductor of the cable 13,
When an abnormal voltage occurs in the sheath and this abnormal voltage is applied to the nonlinear resistance element 2, the nonlinear resistance element 2 is destroyed by the abnormal current based on this abnormal voltage.
At this time of destruction, the internal pressure of the case 18 increases, so that the metal foil 25 is torn. Therefore, even if no abnormal voltage is generated thereafter, if the fact that the metal foil 25 is broken can be detected from the outside through the transparent pipe 22, it is possible to reliably detect that an abnormal voltage has occurred in the sheath.

In the above embodiment, if a part of the transparent pipe 22 is made thin, if the nonlinear resistance element 2 is destroyed by an abnormal current, this abnormal current will flow through the thin part of the transparent pipe 22 and break it. can be prevented from being destroyed and scattered.

(Effects of the invention) According to the invention, a nonlinear resistance element is hermetically housed in a case covered with an insulator, and electrode terminals directly fixed to both sides of the element are made to protrude from the case in an airtight manner, and The protruding part of one electrode terminal was positioned inside the transparent pipe, a communication hole was provided in the electrode terminal to communicate the inside of the case and the transparent pipe, and the opening of the communication hole on the transparent pipe side was hermetically closed with a foil member. This prevents stress from being applied to the nonlinear resistance element due to the expansion and contraction of the insulator, and also prevents the nonlinear resistance element from being destroyed by abnormal current, which increases the internal pressure inside the case and tears the foil member. The occurrence of an abnormal voltage can be reliably detected simply by observing the tear in the foil member from the outside through the transparent pipe.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the cable sheath protection device according to the present invention, Fig. 2 is a front view showing how the device of Fig. 1 is attached to an insulated junction box, and Figs. 3 to 5 are each a conventional cable sheath protection device. It is a sectional view showing a sheath protection device. 2... Nonlinear resistance element, 19, 19'... Electrode terminal, 7, 21... Insulator, 10... Abnormality indicator bar, 11... Solder, 12... Insulated connection box, 15
... Sheath terminal, 18 ... Case, 20 ... Heat shrink tube, 22 ... Transparent pipe, 23 ... Waterproof tape, 24 ... Communication hole, 25 ... Metal foil.

Claims (1)

[Scope of utility model registration request] Connect cables to each other while insulating the sheaths,
A cable sheath protection device that is connected between the pair of sheath terminals of an insulated junction box from which a pair of sheath terminals that are electrically connected to each of the sheaths protrudes, and that is inside a case covered with an insulator. a nonlinear resistance element hermetically housed in the nonlinear resistance element; a pair of electrode terminals each directly fixed to the nonlinear resistance element, protruding airtightly from the case and electrically connected to the pair of sheath terminals; and one of the electrodes. A protruding portion of the terminal from the case extends, and a transparent pipe provided therein, a communication hole provided in the one electrode terminal and communicating the inside of the case and the transparent pipe, and the communication hole communicates with the transparent pipe. A cable sheath protection device comprising: a foil member that airtightly closes on the transparent pipe side.