JPH0132283Y2 - - Google Patents

Description

[Detailed explanation of the invention] A. Field of industrial application This invention does not melt due to shock currents such as those caused by lightning surges, and reliably fuses when exposed to overcurrents at commercial frequencies. This relates to lightning fuses used in high voltage cutouts.

B. Prior Art and Purpose of the Present Invention A high voltage cutout is connected to the primary side of a pole transformer used in an outdoor high voltage distribution line, and this cutout is equipped with a fuse. The characteristics of this fuse are that it can protect the transformer by blowing when an overload or short-circuit current flows, and that it should not blow out against lightning surges that occur during lightning strikes. A power outage accident is used when a fuse with a small current rating using a thin resistance wire is blown due to a lightning surge.

The fuse of the present invention is intended to solve the above-mentioned problems, and is related to a lightning-resistant fuse that does not blow out in response to shock current caused by lightning that is comparable to induced lightning, and that will surely blow out in case of overload current. It is something.

C. Structure of the invention For this purpose, the present invention is constructed by being installed inside an insulating tube 19, and includes a fuse terminal 2 formed in a cap shape, an approximately cylindrical insulating spacer 6, and an insulating spacer 6 interposed therebetween. A relay conductor 7 with a brim-shaped head 7a housed and locked in the bottom 2b of the hollow part of the fuse terminal 2, an electrode 5 whose lower surface is in close contact with the head 7a, and a lower end surface 3 thereof on the upper surface of the electrode 5.
a gap forming member 3 made of a semiconductor or a semiconductive member in close contact with b, and the gap forming member 3;
The electrode 4 whose lower surface is in close contact with the upper end surface 3a of the fuse terminal 2 and which is pushed into the hollow part of the fuse terminal 2, and the relay conductor 7
The inner wall surface 2 of the hollow part of the head 7a and the fuse terminal 2
The auxiliary resistance wire 8 has one end connected to the lower neck part 7b of the relay conductor 7 projecting downward from the fuse terminal 2, and the tip 9a of the auxiliary resistance wire 8 is connected to the other end of the auxiliary resistance wire 8. It is tightly wound around the outer peripheral surface of the connected heat storage metal 9 having a large heat capacity with an insulator interposed therebetween, and one end 11a of the heat storage metal 9 is connected to the fuse terminal 2.
The rear end of the heat storage metal 9 is connected to the rear end of the heat storage metal 9 via a small diameter heat generating resistance wire 11 whose other end 11b is connected to the vicinity of the rear end of the heat storage metal 9, and a low melting point metal 14 that melts due to the heat generated by the heat generating resistance wire. This invention proposes a lightning-resistant fuse characterized by providing a cap-shaped connecting metal 15 connected to the outer peripheral surface 9d in a fitted state.

Hereinafter, embodiments of the present invention will be explained in detail based on FIGS. 1 to 4.

Reference numeral 1 indicates the lightning fuse of the present invention, and 2 in the figure is a fuse terminal formed in the shape of a cap, and a gap forming member 3 formed in the shape of a disk is accommodated in the hollow portion 2a of the fuse terminal. 4 is an electrode which also serves as a blind plug and is in close contact with the upper end surface 3a of the gap forming member; 5;
are plate-shaped electrodes that are in close contact with the lower end surface 3b, and these are fixed by the above-mentioned electrode 4, which is inserted into the hollow part, and the electrode 4 is connected to the fuse terminal 2.
Furthermore, the electrodes 5 are electrically connected via insulating spacers 6 to the heads 7a of relay conductors 7 housed in the bottom 2b of the hollow portion.

In addition, the electrode 5 and the relay conductor, including the gap forming member housed as described above, are exposed to the head 7a of the relay conductor and the inner wall surface 2 of the hollow part when a lightning surge enters.
A space g is formed and insulated to prevent discharge (flash) from directly occurring between the gap forming member and the gap forming member. I have to.

The gap forming member 3 mentioned above may be made of semiconductors made of oxides, chlorides, carbides, sulfides, etc.
Semi-conductive materials such as those coated with semi-conductive paint or semi-conductive rubber on the outer circumferential surface of the insulating material can be used, and these materials exhibit high resistance to commercial frequency current and are highly resistant to lightning surges, etc. For such impact currents, it is suitable to have electrical characteristics such that an external circuit (discharge) can reliably occur on the outer circumferential surface 3c even at a relatively low voltage.

7 is a relay conductor and has a flange-shaped head 7 as described above.
A is locked to the bottom of the terminal, and the lower neck part 7b protruding from the hole 2d is connected to a small diameter auxiliary resistance wire 8, and this resistance wire is crimped to the tip 9a of a pipe-shaped heat storage fitting 9 having a large heat capacity. There is. Reference numeral 6 denotes a heat-resistant insulating spacer made of Teflon resin having a substantially cylindrical shape, and is secured to the terminal so that the flange 6a at the tip is interposed between the head 7a of the relay conductor and the bottom 2b of the terminal. In addition to electrically insulating between the terminal and the relay conductor, the downwardly extending cylindrical portion 6b also covers the lower neck portion 7b of the relay conductor, the auxiliary resistance wire 8, and the vicinity of the center of the heat storage fitting 9. A heating resistance wire 1 is constructed by attaching these relay conductors and auxiliary resistance wires to them using the same spacer.
It is designed to be insulated from 1. Reference numeral 11 is a nichrome wire having one end 11a connected to the bottom outer surface of the fuse terminal by spot welding or half-welding or other suitable means, and the other end 11b similarly connected to the outer peripheral surface 9b near the rear end of the heat storage metal fitting. The resistance wire extends outward and downward along the insulating spacer and is wound particularly tightly around the central portion 9c of the heat storage metal fitting. In addition, a tightly wound coiled heating resistance wire 1
1 is coated with an inorganic adhesive 12, and when this hardens and is fixed to the heat storage metal fitting 9, this adhesive 12 is used to electrically connect the resistance wire 11 from the outer peripheral surface of the heat storage metal fitting 9. It may be insulated.

Reference numeral 13 denotes a resistance wire, and when connecting the resistance wire, the integrally provided cap-shaped connecting fitting 15 is connected to the outer circumferential surface 9b of the end of the heat storage fitting 9 through the low melting point metal 14 in a fitted state. Therefore, when a commercial frequency overcurrent flows, the heat generated by the heating resistance wire is gradually stored in the heat storage metal fitting, and the heat is reliably transferred to the low melting point metal, and the shock current is In the case of instantaneous heat generation, on the other hand, a heat storage metal with a large heat capacity absorbs and radiates the heat, suppressing the temperature rise, and reducing the temperature of low melting point metals.
4. Efforts have been made to prevent heat transfer as much as possible.

16 is a fuse lead wire, which is connected to the resistance wire 13 above.
10 is a pipe-shaped stopper fitting connected to one end, and 18 is an arc-extinguishing tube made of kraft paper, Teflon resin, kraft paper lined with boric acid, etc. arranged so as to surround the outer periphery of the resistance wire 13. , 19 is an insulating tube made of hard vinyl chloride, kraft paper, polycarbonate resin, etc., and 20 is solder.

In addition, as can be seen from the above structure, the fuse of the present invention includes fuse terminal 2 - resistance wire for heat generation, 11 - heat storage fitting 9 - low melting point metal 14 - connection fitting 15 - resistance wire 1.
3-commercial frequency current circuit A of fuse lead wire 16, electrode 4-gap forming member 3-electrode 5-
It consists of an impact current circuit B consisting of a relay conductor 7, an auxiliary resistance wire 8, and a heat storage metal fitting 9. This circuit B is connected in parallel between the fuse terminal 2 of the above circuit A and the heat generating resistance wire 11. The schematic equivalent circuit shown in FIG. 4 is as shown in FIG.

D Effect of the main idea Next, the operation of the fuse according to the present invention will be explained.

As can be seen from the equivalent circuit shown in FIG. 4, the fuse of the present invention, to put it simply, connects the series connection of the gap forming member 3 and the heat storage metal fitting 9 in parallel to the heat generating resistance wire 11, and further connects them with a low melting point metal. The resistance wire 13 is connected in series through the wire 14, and this is further connected between the fuse terminal 2 and the fuse wire 16. If an impact current such as a lightning surge enters, the surge impedance of the heat generating resistance wire 11 will As a result, a voltage drop occurs and this voltage is applied to the electrodes 4 and 5 at both ends of the gap forming member 3 in parallel with the resistance wire, so an external circuit (discharge) occurs on the outer peripheral surface 3c of the gap forming member, which causes an impact. The current flows through the series connection of the gap forming member 3 and the steam heating fitting 9 to the low melting point metal 14 and the resistance wire 13. However, this shock current only flows suddenly, so the temperature of the heat storage metal with a large heat capacity does not rise much.
This does not reach the point where the low melting point metal is melted, and as a result, the fuse is prevented from blowing out. Further, in this case, since almost no impulse current flows through the heat generating resistance wire 11, the resistance wire does not generate heat and naturally does not melt the low melting point metal.

Although the above description was made regarding the passage of the shock current, after the impulse current passes, there is no voltage drop due to the surge impedance of the heating resistance wire, so the gap forming member 3 made of a semiconductor or semiconducting material is insulated on its outer peripheral surface 3c, that is, the electrode The insulation between 4 and 5 is restored, the flashover (discharge) between both electrodes disappears, and current flow to the heat storage metal 9 is blocked, and the commercial frequency load current is transferred to the heat generating resistance wire 11, the low melting point metal 14, and the resistance wire. It only flows on 13.

In addition, if the flowing current is overloaded beyond the rated value, the heating resistance wire generates heat, and this heat is gradually stored in the heat storage metal fitting 9, and its temperature is increased until it reaches a certain temperature (melting point). The melting point metal melts, and the resistance wire 13 to which tension F is constantly applied is pulled out from the low melting point metal, the fuse is blown, and the electrical circuit is opened.

In addition, when a large current flows as in the case of a short-circuit accident, the temperature rises rapidly and the resistance wire 13 having a small heat capacity is fused and the electrical circuit is cut off.

E. Effects of the present invention As described above, in the fuse of the present invention, when an impact current such as a lightning surge flows, external flash is generated in the gap forming member parallel to the heat generating resistor wire, avoiding the current flow to the heat generating resistance wire. Therefore, as a result of the current-carrying circuit consisting of the gap forming member, heat storage metal fittings, and resistance wire passing this shock current, only a small amount of current flows through the heat-generating resistance wire, and the resistance wire generates almost no heat, and the shock current flows as described above. Even in the current-carrying circuit, this shock current flows rapidly, so heat storage metal fittings with a large heat capacity do not store enough heat, and the temperature does not reach the level that melts the low melting point metal, so a thin heat generating resistance wire with a small diameter is used. Even fuses with low current ratings can be reliably prevented from blowing out.

In the above example, external flashing of the gap forming member is caused by the voltage drop caused by the surge impedance of the heating resistance wire, but in this case, the gap forming member is interposed between the electrodes 4 and 5, so that the gap forming member is interposed between the electrodes 4 and 5. Compared to a discharge gap caused by space, the distance between both electrodes can be set to a constant value, so stable discharge characteristics can be obtained. Further, since a semiconductor or a semi-conductive member is used as the gap forming member, external flash can be reliably generated on the outer circumferential surface of the gap forming member even if the voltage drop due to the above-mentioned surge impedance is relatively small. Moreover, because of the creeping discharge, when a lightning surge enters, the discharge starting voltage is constant compared to a simple space gap or a gap forming member made of an insulator, and a more accurate external flash (discharge) operation can be performed.

In addition, when a commercial frequency overload current flows, there is no voltage drop due to the surge impedance of the heating resistance wire, so the gap forming member maintains a high resistance and blocks current flow to the gap forming member, concentrating the current on the heating resistance wire. The heat is then passed through the resistance wire to ensure that it generates heat, and then the heat is gradually stored in the heat storage metal fitting, thereby melting the low melting point metal and blowing out the fuse. Since the heat generated by the metal is tightly wrapped around the outer circumferential surface of the metal fitting and transferred (storage) directly to the heat storage metal fitting, sufficient heat is obtained for the low melting point metal and the metal is reliably melted, making it suitable for small-diameter heat generation. Even though resistance wire is used, time lag characteristics and accurate fusing characteristics can now be obtained.

[Brief explanation of the drawing]

1 to 4 show embodiments of the present invention. FIG. 1 is a vertical cross-sectional view of the lightning fuse of the present invention, FIG. 2 is an enlarged vertical cross-sectional view of the vicinity of the fuse terminal in FIG. 1, and FIG. The figure is an enlarged vertical cross-sectional view of the vicinity of the heat storage metal fitting shown in FIG. 1, and FIG. 4 is a schematic diagram showing the lightning protection fuse shown in FIG. 1 using an electrical equivalent circuit. 1 ...Lightning fuse, 2...Fuse terminal, 3
...Gap forming member, 4, 5... Electrode, 6...
Insulating separator, 7... Relay conductor, 8... Auxiliary resistor, 9... Heat storage metal, 11... Resistance wire for heat generation,
13...Resistance wire, 14...Low melting point metal, 15...
Connection fittings, 16... Fuse lead wire, 19...
Insulating tube, g...space.

Claims (1)

[Scope of utility model registration request] It is configured to be installed inside an insulating tube 19, and includes a fuse terminal 2 formed in a cap shape, an approximately cylindrical insulating spacer 6, and a hollow portion of the fuse terminal 2 via the insulating spacer 6. A relay conductor 7 with a brim-shaped head 7a housed and locked on the bottom 2b, an electrode 5 whose lower surface is in close contact with the head 7a, and a semiconductor or semiconductive member whose lower end surface 3b is in close contact with the upper surface of the electrode 5. a gap forming member 3, an electrode 4 whose lower surface is in close contact with the upper end surface 3a of the gap forming member 3 and pushed into the hollow part of the fuse terminal 2, a head 7a of the relay conductor 7, and a hollow part of the fuse terminal 2. A space g formed between the inner wall surface 2c of the Its tip 9a
A small-diameter wire is tightly wound around the outer peripheral surface of a heat storage metal 9 having a large heat capacity connected to the heat storage metal 9 through an insulator, and one end 11a thereof is connected to the fuse terminal 2 and the other end 11b is connected to the vicinity of the rear end of the heat storage metal 9. A cap-shaped connecting metal 15 is connected in a fitted state to the rear end outer circumferential surface 9d of the heat storage metal 9 via the heat generating resistance wire 11 and the low melting point metal 14 which melts due to the heat generated by the heat generating resistance wire. A lightning-resistant fuse characterized by being equipped with.