JPS6281006A - Lightining porcelain and manufactruing thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Purpose of the Invention (Field of Industrial Application) The present invention relates to a lightning arrester having a built-in lightning arrester element, and more particularly relates to a lightning arrester used in an insulator device for an overhead power transmission line. be.

(Prior art) The applicant of the present application previously developed a lightning arrester insulator with a built-in lightning arrester.
In Japanese Patent Application No. 60-84956, the system shown in FIG. 13 was proposed. In this lightning arrester, a clamping fitting 53 is screwed onto the lower inner circumferential surface of a cylindrical power supply side mounting fitting 52 that is fitted and fixed to the lower end of a voltage-resistant insulating cylinder 51.
It is fitted into a spring holding fitting 55 provided at the lower end of the element assembly 54 housed in the element assembly 1, and is prevented from loosening by a stop ring 56. A spring receiver metal fitting 57 is screwed onto the inner circumferential surface of the tightening metal fitting 53.

Further, a bottomed cylindrical current-side electrode 58 is screwed and fixed to the lower outer peripheral surface of the power-side mounting bracket 52, and the annular protrusion 58a near the center of the bottom of the electrode 58 and the spring receiver are connected to a metal fitting. A plurality of disc springs 5 for preventing loosening of the voltage-applying side electrode 58 are provided between the electrode 57 and the electrode 57.
9 is interposed.

A rubber mold 60 is formed between the voltage-resistant insulation tube 51 and the element assembly 54 and on the outside of the voltage-resistant insulation M51.

(Problems to be Solved by the Invention) However, the above-mentioned lightning arrester has a large number of parts, has a complicated structure, and requires time and effort to manufacture, resulting in high manufacturing costs.

An object of the present invention is to provide a lightning arrester that solves the above problems.

Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the first invention provides a voltage-resistant insulating tube 2.
A cylindrical ground side electrode 22 and a bottomed cylindrical energized side electrode 23 are fitted and fixed to the upper and lower ends of 1, respectively, and a plurality of lightning arrester elements 29 are stacked in series between the two electrodes. The element assembly 2 is housed in the energizing side electrode 23.
A concave portion or a convex portion is provided on the inner periphery of the ground side electrode 22 to restrict the position of the element presser metal fitting 31 provided at the lower end of the ground side electrode 22, and to restrict the position of the element presser metal fitting 31 in a concavity-convex relationship with the element presser metal fitting 31 provided at the lower end of the ground electrode 22.
e is provided and the clamping fitting 25 is screwed together. A spring 39 for crimping the element assembly 28 is interposed between the element assembly 28 and the voltage-resistant insulation cylinder 21 and between the element assembly 28 and the voltage-resistant insulation cylinder 2.
A configuration in which a rubber mold 42 is provided on the outer periphery of the rubber mold 42 is adopted.

Further, in the second invention, after a cylindrical grounding side electrode 22 and a bottomed cylindrical energizing side electrode 23 are fitted and fixed to the upper and lower ends of the voltage-resistant insulating cylinder 21, a plurality of lightning arresters 29 are stacked in series. The element assembly 28 configured as above is housed in the voltage-resistant insulating cylinder 21 from the ground side electrode 22 using an operating rod, and the element holding fitting 31 provided at the bottom of the open assembly 28 is connected to the voltage-side electrode 23 due to the unevenness. The spring 39 and the terminal fitting 37 for receiving the spring 39 are inserted into the upper part of the element holding fitting 30 on the upper part of the element assembly 28 by engaging with the provided recess or protrusion, and the tightening fitting 25 is connected to the ground side electrode 22. The terminal fitting 37 is screwed into the provided female screw 22e and pushed in against the biasing force of the spring 39, and the element assembly 28 is fixed between the energizing side electrode 23 and the terminal fitting 37. The element assembly 28 and the voltage-resistant insulation cylinder 21 are housed in the mold.
A configuration in which a rubber mold 42 is provided between the two and around the outer periphery of the voltage-resistant insulating cylinder 21 is adopted.

(Function) Since the above-mentioned means is adopted, in the first invention, even if external forces such as bending or tension due to loading during construction, earthquakes, or electric wire vibrations are applied, these are all borne by the voltage-resistant insulating tube and the rubber mold. Therefore, the coating and the element are not affected, the coating and the element are prevented from being cracked, and the lightning arrester is prevented from being damaged. Furthermore, even if an arc occurs in the element part, the voltage-resistant insulating tube bears the burden, so no scattering damage occurs.

Moreover, the second invention houses the element assembly from the grounding side electrode into the voltage-resistant insulating cylinder in which a cylindrical ground side electrode and a bottomed cylindrical energized side electrode are fitted and fixed at both upper and lower ends, respectively. Then,
Due to the unevenness of the element mounting bracket provided at the bottom of the open assembly, it is easily engaged with the recess or protrusion provided on the power-supplying side electrode, and the tightening fitting is screwed into the female thread provided on the grounding side electrode. By simply fitting them together, the element assembly is fixed between the energizing side electrode and the terminal fitting disposed on the upper part of the element assembly.

(Example) An example embodying the first invention will be described below with reference to FIGS. 1 to 8. As shown in FIG. 1, a hanging metal fitting 2 is tightened and fixed to the steel tower 1 with bolts 3, and a hanging metal fitting 4 is supported on the hanging metal fitting 2 so as to be perpendicular to the hanging metal fitting 2. A connecting yoke 6 is supported on the hanging fitting 4 via a connecting pin 5, and hanging insulators 7, 7 are rotatably supported at both left and right ends of the connecting yoke 6 via connecting pins 8, respectively. .

First connecting links 10 and 10 are supported at the lower ends of the lower insulators 7 and 7 through connecting pins 9, and both links 1
0.10 is connected to the connecting yoke 1 via the connecting pin 11.11.
2 is supported. The connecting yoke 12 has a connecting pin 1.
A second connecting link 14 is supported via the link 1
4 supports a clamp 16 via a connecting pin 15,
An electric wire 17 is suspended and supported by this clamp 16. A discharge electrode 12a is provided at the center of the upper surface of the connection yoke 12.

Further, a bracket 18 No. 3.4 is provided at the center of the connection yoke 6.
As shown in the figure, a voltage-resistant insulating tube 21 made of a material such as reinforced plastic (FRP) that has excellent mechanical strength, heat resistance, and pressure resistance has a cylindrical ground side electrode with a stepped portion 22a at the upper end. 22, bottomed cylindrical power supply side electrodes 23 are respectively fitted to the lower ends and fixed with an adhesive 24.

Note that an annular groove 21a is formed on the outer circumferential surface of both ends of the voltage-resistant insulating tube 21, and annular grooves 22b and 23a are formed on the inner circumferential surfaces of the ground side electrode 22 and the energized side electrode 23 to increase the bonding area. It strengthens the adhesion.

A mounting flange 22C is formed on the upper outer periphery of the ground side electrode 22, and a plurality of mounting flange 22C (in this embodiment) are used to fix the lightning arrester 20 to the bracket with bolts 49 (see FIG. 1). In 8), an insertion hole 22d for a bolt is provided. In addition, in the upper, center and lower part of the voltage-resistant insulating cylinder 21, there are 1 holes in the diameter direction of the insulating cylinder 21
Gas escape holes 21b (see FIG. 5) are formed every 80°. It is efficient to provide the gas escape hole 21b near the ground side electrode 22 and the charged side electrode 23 and near the intermediate part thereof. Note that the gas escape hole 21b has a diameter of 90 mm.
It may be formed for each degree.

A cylindrical engagement tube 23b is provided protruding from the bottom center of the energizing side electrode 23. In addition, around the engaging tube 23b, there are a plurality of through holes 23 to allow gas to escape and to distribute the rubber (during the formation of a rubber mold 42, which will be described later).
c is transparent.

Further, the horn mounting bracket 26 welded to the lower surface of the energizing side electrode 23 is provided with a through hole 26a for a bolt.
, 2, the discharge electrode 27 is attached with 50 bolts,
An air discharge gap G is formed between the connection yoke 12 and the discharge electrode 12a.

An element assembly 28 is accommodated within the voltage-resistant insulation cylinder 21 . This element assembly 28 is connected to a plurality of lightning arrester elements 29 which are stacked in series and whose voltage-current characteristics are non-linear and which is mainly made of zinc oxide, and is connected to the upper part of the lightning arrester element 29.
0a and a screw hole 30 provided in the center of the accommodation recess 30a.
It is composed of an element holding fitting 30 having a shape b, an element holding fitting 31 joined to the lower part of the lightning arrester 29, and a covering 32 made of EPDM rubber provided on the outer periphery of the lightning arresting element 29 and the pixel holding fitting 30.31. has been done.

In addition, the same wave ff132 is the upper and lower pixel holding metal fittings 30.31
It extends to the end face of.

As shown in FIG. 7, a metallicon 33 is applied to both the upper and lower surfaces of each lightning arrester element 29, and a conductive spacer 34 made of a thin plate of soft metal (lead in this embodiment) is interposed between each element 29. The electrical connection between each lightning arrester element 29 is improved. Further, an insulating layer 35 is formed on the outer peripheral surface of each lightning arrester element 29, and a U-shaped annular groove 36 formed by the insulating layer 35 and the conductive spacer 34 prevents the arc from flying.

The ri 32 prevents deterioration of the lightning arrester element 29 due to moisture absorption, displacement due to vibration, etc., and prevents rubber from entering between the lightning arrester elements 29 during molding of the rubber mold 42 described later, and furthermore, the element assembly 28 is made more compact. Insulator 2
0 miniaturization becomes possible. The coating 32 is formed to have a thickness of 1 to 4 m++ so as to fit within the annular groove 36 shown in FIG. 7 without creating any gaps. By adhering the coating 32 and the lightning arrester element 29, it is possible to more completely prevent the generation of voids, and it is also possible to improve the element holding function.

A conductive spacer 34 is also interposed between the lightning arrester element 29 and the upper element holding fitting 30 and the lower element holding fitting 31.

A female thread 22e is formed on the lower inner peripheral surface of the ground side electrode 22, and as shown in FIG. 3, a fastening fitting 25 having a male thread 25a is screwed onto the outer peripheral surface. Between the terminal fitting 37, which is fixed through the insertion hole 25b at the center of the tightening fitting 25 via a cylindrical insulating spacer 38, and the element holding fitting 3° on the upper part of the element assembly 28, the element assembly 28 to the same terminal fitting 3
A spring 39 is crimped and fixed between the energizing side electrode 23 and the lightning arrester element 29, and its upper end is inserted into the accommodation recess 37a of the terminal fitting 37, and its lower end is inserted into the element holding fitting 30. It is housed and interposed within the housing recess 30a. Note that shunts 40 are interposed at one or more locations (three locations in this embodiment) in the spring 39 to improve electrical connection.

Further, a buffer member 41 is screwed onto the lower surface of the terminal fitting 37 to soften the impact force on the shunt 40 when mold rubber is injected, which will be described later.

The lower element holding fitting 31 has a protrusion 31a whose position is regulated by an uneven relationship with the engagement tube 23b of the energizing side electrode 23.
The protrusion 31a is provided with a tapered surface 31b that becomes narrower toward the lower end to facilitate insertion into the engagement tube 23b and to maintain electrical contact. It has become.

A rubber mold 42 made of heat-shrinkable EPDM rubber is formed between the voltage-resistant insulation tube 21 and the element assembly 28, between the ground side electrode 22 and the terminal fitting 37, and on the outside of the voltage-resistant insulation w121. It extends to the lower outer circumferential surface of the side electrode 22 and the upper outer circumferential surface of the energized side electrode 23, and a pleat 42a is integrally formed on the outer circumference. This rubber mold 4
2 is EPDM rubber in a fluid state at about 150°C.
It is molded by injection at a pressure of about 0 kg/cnl.

Annular grooves 2 on the inner side of the upper part and the outer side of the lower part of the ground side electrode 22
2f, the annular groove 23d on the outside of the power-supplying side electrode 23, the annular groove 37b on the outer periphery of the terminal fitting 37, the inside and outside of the voltage-resistant insulating tube 21, and the outside of the ri 132 of the element assembly 28 are filled with EPDM under the condition of injectability when injecting EPDM rubber. Vulcanized adhesive is applied in advance to bond the rubber and metal and improve airtightness. The rubber mold 42 between the energizing side electrode 23 and the element assembly 28 is formed by letting the gas escape from the through hole 23c so that the rubber is spread throughout the space between the grounding side electrode 22 and the terminal fitting 37. The rubber mold 42 is formed of rubber that flows into the through hole 25c formed in the fastening fitting 25 during molding.

Further, as shown in FIG. 5, the rubber mold 42 is provided with a pressure release port 42b at a position corresponding to the gas release hole 21b of the pressure-resistant insulating cylinder 21.

The lightning arrester 20 is attached to the connecting yoke 6 so that the pressure relief port 42b is perpendicular to the electric wire 17, so as to prevent the hanging insulator 7 from being burnt out due to arc discharge during an abnormality.

As shown in FIG. 1, an arcing ring arm 43 is fixed to an example of the bracket 18, and an arcing ring 44 is provided at the tip of the arcing ring arm 43 so as to correspond to the upper pressure release port 42b. ing. On the other hand, an arcing ring arm 43 is also fixed to the horn mounting bracket 26 of the energizing side electrode 23 with a bolt, and an arcing ring is formed at the tip of the arcing ring arm 43 so as to substantially correspond to the lower pressure relief port 42b. A ring 44 is provided.

Next, a method for manufacturing a lightning arrester according to the second invention will be explained.

First, the ground side electrode 22 and the energized side electrode 23 are fitted and fixed to the upper and lower ends of the voltage-resistant insulating cylinder 21, respectively, using a resin adhesive 24. Next, the inside and outside of the voltage-resistant insulating cylinder 21, the grounding side electrode 22, and the voltage-supplying side electrode 23, and the cover 5132 of the element assembly 28 are
A screw hole 30b is formed in the element fitting 30 on the upper part of the element assembly 28 which has been formed in advance by applying a vulcanizing adhesive to the outside.
The element assembly 28 is housed in the voltage-resistant insulating cylinder 21 from the ground side electrode 22 by screwing together an operating rod (the path shown in the figure) having a male thread therein, and an element bracket provided at the bottom of the open assembly 28 The protrusion 31a of 31 is connected to the engaging cylinder 23 of the power-supplying side electrode 23 due to its unevenness.
After engaging in the inside of b to restrict the position of the element assembly 28, the operating rod is removed.

Next, the spring 39 with the shunt 40 interposed therein is accommodated in the accommodation recess 30a of the element fitting 30 on the upper part of the element assembly 28, and the upper end of the spring 39 is accommodated in the accommodation recess 37a of the terminal fitting 37. Insert the insulating spacer 38 into the metal fitting 37,
Further, the fastening fitting 25 is fitted to the insulating spacer 38. After this, the terminal fitting 37 is attached to the spring 3 using a jig (the path shown in the figure).
9, and screw the tightening fitting 25 onto the female thread 22e of the grounding side electrode 22 to tighten the insulating spacer 3.
Press 8. Then, the pressing by the jig is released, and the fixing of the element assembly 28 is completed.

Next, the voltage-resistant insulating cylinder 21 with the grounding side electrode 22 and the voltage-bearing side electrode 23 fitted and fixed is housed in a mold (not shown), and rubber is injected to form a voltage-resistant insulating cylinder 21 between the element assembly 28 and the voltage-resistant insulating cylinder 2I. A rubber mold 42 is formed around the outer periphery of the insulating cylinder 2I, the ground side electrode 22, and the energized side electrode 23, and the manufacturing of the lightning arrester 20 is completed.

Next, the operation of the insulator device constructed as described above will be explained.

Now, when a lightning surge enters the electric wire 17 due to a lightning strike, the current is arc-discharged from the electric wire 17 to the discharge electrode 27 from the discharge electrode 12a of the clamp 16-second connection link 14 connection yoke 12 through the air discharge gap G. , flows from the energizing side electrode 23 to the lightning arrester element 29 via the lower element part fitting 31,
Furthermore, it flows from the steel tower 1 to the ground via the upper element fitting 30, 40, terminal fitting 37, and connecting yoke 6.

The subsequent current caused by this is blocked by the lightning arrester element 29.

Furthermore, if the M snow element 29 is abnormally discharged due to an unexpected large-scale lightning strike and a high-temperature, high-pressure arc is generated, a part of the coating 32 and a part of the rubber mold 42 near the gas escape hole 21b of the voltage-resistant insulating cylinder 21 will be damaged. It is softened or melted and destroyed, and is blown away by high-pressure gas, forcibly forming an arc discharge path leading to the outside. The arc emitted to the outside of the insulator 20 is transferred between both arcing rings 44, and the upper and lower arcs are connected to each other.

Now, in the embodiment of the present invention, an engaging cylinder 23b is formed on the energizing side electrode 23 to restrict the position of the element part fitting 31 at the lower part of the element assembly 28 through a concave and convex relationship.
A tightening fitting 25 is screwed into the internal thread 22e formed in the 22e, and a spring 39 for crimping and fixing the element assembly 28 between the energizing side electrode 23 and the terminal fitting 37 and a terminal fitting 37 for receiving the spring 39 are screwed together. , the tightening fitting 25 and the upper element part fitting 30.
Since it is interposed between them, the number of parts can be reduced compared to conventional lightning arrester insulators, and manufacturing costs can be reduced.

In addition, even if external forces such as bending or tension due to loading during construction, earthquakes, or vibration of electric wires are applied, all these forces can be borne by the voltage-resistant insulating tube 21 and the rubber mold 42.
It does not affect the coating 32 or the element part, and the
2 and the lightning arrester element 29 can be prevented from cracking and breaking, and the lightning arrester 2o
damage can be prevented. In addition, even if an arc occurs in the element part, the pressure-resistant insulating tube 21 will take care of the arc.
It can prevent scattering damage.

In addition, in this embodiment, the lightning arrester element 29 is enclosed in the sheath 32 together with the terminal fitting 37 and the element mounting fittings 30 and 31 at both the upper and lower ends, so that the lightning arrester element 29 can be stacked and fixed in a compact manner, and the storage space for the lightning arrester element 29 can be reduced. The insulator 20 can be made smaller and workability can be improved.

Further, since the lightning arrester element 29 is tightly wrapped with the covering 32 and the rubber mold 42, it is possible to prevent the lightning arrester element 29 from shifting due to vibrations, etc., and to prevent moisture absorption deterioration of the lightning arrester element 29.

Furthermore, since the lightning arrester element 29 is built in by the pressure-resistant insulating tube 21 made of FRP and the rubber mold 42, the mechanical strength is improved and the lightning arrester 20 can be significantly reduced in weight.

Furthermore, in this embodiment, the thickness of the coating 32 is 1 to 4 mm, so it fits inside the annular groove 36 and does not form a gap.
Therefore, deterioration of the lightning arrester element 29 due to corona discharge can be prevented.

In addition, since the pressure-resistant insulating cylinder 21 is made of FRP that can withstand the temperature and pressure during rubber molding, reliability of mechanical strength can be ensured during the manufacturing process, and the ground side electrode 22
This prevents the voltage-applying side electrode 23 from falling off and the voltage-resistant insulating cylinder 21 from deforming.

Note that the present invention is not limited to the above embodiments, and may be implemented as follows.

(1) As shown in FIG. 9, three arcuate protrusions 23e are formed at equal intervals on the same circumference with respect to the voltage-applying side electrode 23.
, and the protrusion 3 of the element fitting 31 is formed between the protrusions 23e.
1a. Also, two or four or more of the same protrusions 23e may be provided.

(2) A recess is formed in the bottom of the energizing side electrode 23 to accommodate the protrusion 31a of the element mounting bracket 31.

(3) A protrusion is formed in the center of the energizing side electrode 23, a recess is formed in the element fitting 31, and the protrusion and the recess are engaged.

(4) As shown in FIG. 10, a self-fusing tape 45 is wound around the outer periphery of the lightning arrester 29, the upper element fitting 30, and the lower element fitting (not shown) to form the element assembly 28. to do.

(5) Rubber adhesive is applied to the outer peripheries of the M lightning element 29 and the element fitting 30 to form the element assembly 28.

(6) As shown in FIG. 11, the element assembly 28 is constructed by connecting the upper element fitting 30 and the lower element fitting (not shown) using a plurality of connecting plates 46 made of FRP. . In this case, the connecting plate 46 is fixed to the upper and lower element fittings by screws 47 or adhesive. Further, seals 48 are applied between each lightning arrester element 29 using a rubber adhesive as shown in FIG.

(7) The conductive spacer 34 interposed between each lightning arrester element 29 in the above embodiment can be omitted.

(8) The rubber mold 42 may be made of silicone rubber or butyl rubber instead of EPDM rubber.

Effects of the Invention As detailed above, according to the present invention, the number of parts can be reduced and the structure can be simplified compared to conventional lightning arrester insulators, and the work process can be simplified and manufacturing costs can be reduced.

In addition, even if external bending or tensile forces are applied due to loads during construction, earthquakes, or wire vibrations, all of these forces can be borne by the voltage-resistant insulating cylinder and rubber mold, so there is no effect on the covering or element parts. , cracks and damage to the coating and elements can be prevented, and damage to the lightning arrester can be prevented. Furthermore, even if an arc occurs in the element part, the pressure-resistant insulating cylinder takes on the burden and has the excellent effect of preventing scattering destruction.

[Brief explanation of drawings]

Fig. 1 is a front view showing an insulator device equipped with the lightning arrester of the present invention, Fig. 2 is a front view showing the lightning arrester, Figs. A-A in Figure 3
6 is an end view taken along line B-B in FIG. 4, FIG. 7 is a partially enlarged sectional view of the lightning arrester, FIG. 8 is an end view taken along line C-C in FIG. 3, and FIG. 9 is an end view taken along line C-C in FIG. A perspective view showing another example of the energizing side electrode, 1st
Figure 0 is a partial perspective view showing another example of the element assembly, Figure 11 is a partial front view showing another example of the element assembly, Figure 12 is an enlarged sectional view showing the connected state of the lightning arrester element, and Figure 13 is a partial perspective view showing another example of the element assembly. FIG. 2 is a longitudinal cross-sectional view showing a conventional lightning arrester. 21... Voltage-proof insulating tube, 22... Ground side electrode, 22e
...Female thread, 23...Electricity side electrode, 25...Tightening fitting, 29...Lightning arrester element, 30.31...Element holding fitting, 32...Coating, 37...Terminal Metal fittings, 39...
・Spring, 42...Rubber mold. Patent applicant Agent: Nippon Insulator Co., Ltd.
Person Patent Attorney On 1) Hironobu Figure 13

Claims (1)

[Claims] 1. A cylindrical ground side electrode (22) and a bottomed cylindrical power supply side electrode (23) at both upper and lower ends of the voltage-resistant insulating cylinder (21), respectively.
At the same time, multiple lightning protection elements (
29) are stacked in series. A recess or a convex portion is provided to restrict the position of the element holding fitting (31) and connect it, and a tightening fitting (25) is attached to the female screw (22e) provided on the inner periphery of the ground side electrode (22). between the element holding fitting (30) provided at the upper end of the element assembly (28) and the tightening fitting (25).
A spring (39) for crimping the element assembly (28) is interposed between the element assembly (23) and the terminal fitting (37), and a spring (39) is interposed between the element assembly (28) and the voltage-resistant insulation cylinder (21) and the voltage-resistant insulation tube (21). A lightning arrester characterized in that a rubber mold (42) is provided on the outer periphery of an insulating cylinder (21). 2 The voltage-applying side electrode (23) is made of rubber with a pressure-resistant insulating tube (21).
) The lightning arrester according to claim 1, further comprising a through hole (23c) for passing through the lightning arrester. 3. The power supply side electrode (23) is integrally provided with a horn mounting bracket (26) having a bolt insertion hole (26a) for mounting the discharge electrode (27). Lightning arrester described in . 4 The ground side electrode (22) has a bolt insertion hole (22).
d) The lightning arrester according to claim 1, which is integrally provided with a mounting flange (22c) having a mounting flange (22c). 5 After fitting and fixing the cylindrical ground side electrode (22) and the bottomed cylindrical energized side electrode (23) to the upper and lower ends of the voltage-resistant insulating tube (21), respectively, a plurality of lightning arrester elements (29) are connected in series. The element assembly (28), which is constructed by stacking the two layers, is housed in the voltage-resistant insulating cylinder (21) from the ground side electrode (22) using the operating rod, and the element holding fitting (31) provided at the bottom of the open assembly (28) is ) is engaged with the concave or convex portion provided on the voltage-side electrode (23) due to the unevenness, and the element holding fitting (30) on the upper part of the element assembly (28) is engaged.
) Insert the spring (39) and the terminal fitting (37) for receiving the spring (39) into the upper part, and tighten the tightening fitting (25) to the female screw (22e) provided on the ground side electrode (22). Screw together the fitting (25) and attach the terminal fitting (37) to the spring (
39) to fix the element assembly (28) between the energizing side electrode (23) and the terminal fitting (37), and then housed in a mold to remove the element assembly (28). 28) and a voltage-resistant insulating tube (21), and a rubber mold (42) is provided on the outer periphery of the voltage-resistant insulating tube (21).