JPH0243084Y2 - - Google Patents

Description

[Detailed description of the invention] Purpose of the invention (industrial application field) This invention relates to an improvement of a current-limiting fuse used for high-voltage cut-outs, and relates to a current-limiting fuse that has multiple lightning protection measures.

(Prior art) Current-limiting fuses used for high-voltage cut-outs have extremely high dielectric strength inside the fuse after the current-limiting fuse has cut off, so if abnormal high voltage enters due to multiple lightning strikes, etc. in such a state, the fuse will break. A flash short occurs between the upper and lower electrodes outside the outer cylinder, and the commercial frequency from the power supply is superimposed on this, causing a follow-on current to flow, and the arc jet at this time causes damage to the current limiting fuse, high voltage cutout, etc. There was a risk that it would cause destruction.

Therefore, the present applicant has already proposed in Utility Model Application Publication No. 57-89248 that a flash-flash electrode is installed inside a current-limiting fuse, with one end connected to one fixed electrode and the other end facing the other fixed electrode with a gap. However, in this case, residual arc extinguishing agent was used to block the following flow, so there was a problem in that it was difficult to control the amount of arc extinguisher filled, etc. during manufacturing.

(Problems to be Solved by the Invention) This invention was devised to solve the above-mentioned problems, and its purpose is to eliminate external flash faults after the current-limiting fuse is cut off by multiple lightning strikes.

Structure of the invention (means for solving problems) The current limiting fuse of this invention has a fuse element connected between the upper electrode and the intermediate electrode fixed to both upper and lower ends of the insulating outer cylinder, and an insulating core arranged. Furthermore, in the current limiting fuse provided with a lower electrode connected to the intermediate electrode, a pair of electrode rods electrically connected in parallel to the fuse element are disposed within the insulating core and spaced apart from each other via a discharge gap. In addition, the discharge gap is set so that the distance between the upper and lower electrodes is shorter than that between the upper and lower electrodes, and an arc extinguishing tube is provided in the insulating core to cover the tip of the electrode rods. It is something to do.

(Function) When a second wave of lightning surge enters after the fuse element melts due to the first wave of lightning surge such as multiple lightning and cuts off the follow-on current of the commercial frequency, the electrode with low pressure resistance connected in parallel with the fuse element This voltage is applied between the rods, an arc is generated in the discharge gap, and a commercial frequency is superimposed on this to generate a follow-on current. This follow-on arc is extinguished by the excellent slit arc-extinguishing effect of the arc-extinguishing tube placed between the electrode rods and the arc-extinguishing gas of the arc-extinguishing tube generated by the arc heat, and the follow-on current is blocked. Ru.

(Example) The first example that embodies this idea will be described below.
This will be explained with reference to FIGS.

In Figure 1, the high voltage cut-out PC attached to a cross arm such as a utility pole has its upper fixed electrode (not shown) connected to the high voltage underline L1 on the power supply side, and its lower fixed electrode (not shown) on the load side. It is connected to the primary side of the transformer Tr via a high voltage underline L2. Insulation coordination is achieved so that the charging part of the transformer bushing B and the transformer case C are the weakest point in terms of insulation level.

To explain the current-limiting fuse F, which is attached to the high-voltage cut-out PC and is arranged so as to be able to connect to and separate from its upper and lower fixed electrodes (not shown), the upper end of the insulating outer cylinder 1 of the current-limiting fuse F (the left side in FIG. ) is fitted and fixed with a cylindrical upper electrode fitting 3 having an upper contact blade 2 projecting thereon as an upper electrode.

As shown in FIG. 3, three support protrusions 3 are provided at equal angles on the inner peripheral surface of the opening 3a of the upper electrode fitting 3.
b is integrally provided in a protruding manner. A lower electrode fitting 4 having a lower contact blade 5 as a lower electrode protruding in the same direction as the upper contact blade 2 is fixed to the center of the insulating outer cylinder 1. The lower electrode fitting 4 is provided with a connecting portion 6 that protrudes toward the lower end of the insulating outer cylinder 1;
One end of a conductive plate 7 bent in a stepped manner is connected to the connecting portion 6 with a screw 8 . At the other end of the conductive plate 7, a ring-shaped intermediate electrode 9 is integrally formed, which extends along the longitudinal direction of the outer periphery of the insulating outer cylinder 1 toward its lower end and comes into contact with the lower end surface of the insulating outer cylinder 1. has been done.

Further, a through hole 9a for inserting the insulating core 11 is formed in the intermediate electrode 9, and an element drawer recess 9b is formed in the through hole 9a. An engaging piece 10 that abuts and engages the outer periphery of the insulating outer cylinder 1 is provided on the conductive plate 7 on the side 180 degrees opposite to the conductive plate 7 . Further, the lower end of the insulating outer cylinder 1 is covered with a cap-shaped protective cover 19 made of an insulating material, and a thin wall portion 20 is formed at the inner bottom of the protective cover 19 corresponding to the intermediate electrode 9. . An epoxy resin adhesive is filled between the protective cover 19 and the insulating cylinder 1 in a watertight manner.

An insulating core 11 made of alumina porcelain or the like is housed in the inner axial direction of the insulating outer cylinder 1. The outer periphery of the upper end of the insulating core 11 is stably supported and fixed by the support protrusion 3b of the upper electrode fitting 3, and the center position of the insulating core 11 is determined, and the lower end of the insulating core 11 is connected to the intermediate electrode 9.
It is placed in contact with the In addition, in the upper electrode fitting 3, the upper end of the fitting hole 3a is formed with a stepped portion 3c whose diameter is larger than that of the fitting hole 3a, a conductive stopper plate 12 is fitted in the stepped portion 3c, and the insulating core It is arranged so as to close the upper end opening of 11.

A fuse element 13 is wound around the outer periphery of the insulating core 11, and its upper end is connected to the stop plate 12.
It is inserted through an element through hole 12a provided in the center of the element and fixed by soldering. or,
The lower end of the fuse element 13 is connected to the outer surface of the intermediate electrode 9 via the element extension recess 9b of the intermediate electrode 9.

An electrode rod 14 is inserted from the upper end of the insulating core 11, and its base end closes the upper end opening of the insulating core 1 and is electrically connected to the upper electrode fitting 3. An electrode rod 15 is inserted from the lower end of the insulating core 11, and a mounting plate 15a having a plurality of discharge holes 15b is formed at its base end.

The mounting plate 15a is placed in contact with the lower end opening of the insulating core 1 so that the discharge hole 15b corresponds to the opening of the insulating core 11, and is electrically connected to the intermediate electrode 9. Further, the tips of the electrode rods 14 and 15 are arranged opposite to each other with a discharge gap 16 so as to be shorter than the insulation distance between the upper contact blade 2 and the lower contact blade 5.

That is, both electrode rods 14 and 15 are electrically connected in parallel to the fuse element 13 via a discharge gap 16 having a certain distance, and when the current-limiting fuse F is in a non-blown state, the current-limiting fuse F is It does not affect functionality in any way. Further, an arc extinguishing tube 17 made of Teflon or the like is inserted into the insulating core 11 so as to cover the discharge gap 16 and the tips of the electrode rods 14 and 15. Incidentally, arc-extinguishing sand 18 is filled between the insulating outer cylinder 1 and the insulating core 11.

The action of the current limiting fuse F configured as described above will be explained.

Now, under normal conditions, the high voltage cut-out wire L1 on the power supply side is connected to the upper fixed electrode of the PC main body (not shown) → the upper contact blade 2 of the current limiting fuse F → the fuse element 13 → the intermediate electrode 9 → the conductive plate 7 → the lower contact The circuit configuration is from the blade 5 to the lower fixed electrode of the high voltage cutout PC main body (not shown) to the high voltage underline L2 on the load side to the primary side of the transformer Tr.
In this state, since there is a discharge gap 16 between the electrode rods 14 and 15 in the current limiting fuse F, no current flows.

In this state, if the first wave of lightning surge (abnormal voltage) etc. intrudes due to multiple lightning strikes, etc., the weakest point in terms of insulation level, the live part of the transformer bushing B and the case C of the transformer Tr, A flashover occurs, and the commercial frequency is superimposed on this, resulting in a follow-on current. This follow-on current is interrupted by the fuse element 13 of the current-limiting fuse F being blown out, and the dielectric strength within the current-limiting fuse becomes extremely high.

Subsequently, when a second wave of lightning surge (abnormal voltage) enters, voltage is applied between the upper and lower electrode fittings 3 and 4 outside the insulating outer cylinder 1 due to the above condition, but at the same time, the fuse disposed inside the insulating core Electrode rods 14 and 15 with low pressure resistance arranged in parallel with the element 13
A voltage is applied to the discharge gap 1 between the electrode rods 14 and 15 from between the upper and lower electrode fittings.
6 is in a close position, internal flashing takes priority over external flashing outside the outer cylinder, and the commercial frequency is superimposed on this, resulting in a follow-on current.
This follow-on arc continues to be extinguished by the slit arc extinguishing action of the arc extinguishing tube 17 placed between the electrode rods 14 and 15 and the arc extinguishing gas of the arc extinguishing tube generated by the arc heat. cut off the flow.

Furthermore, if the pressure inside the insulating core 11 rises abnormally due to this interruption, the thin part 20 of the protective cover 19 will be broken through the discharge hole 15b provided in the electrode rod 15, and the pressure will be released to the outside, thereby limiting the current. Fuse F will not be destroyed.

Therefore, in the event of multiple lightning strikes, the current limiting fuse F
The discharge gap 1 between the upper and lower electrode rods 14 and 15 precedes the external flash between the upper and lower contact blades 2 and 5 that occurs in
Since an arc is generated in the tube 6 and the arc is reliably extinguished by the arc extinguishing tube 17, subsequent flow can be reliably blocked.

Therefore, unlike in the past, no external flash occurs in the current-limiting fuse F, and uneven heat damage to the high voltage cut-out due to this external flash and scattering due to uneven heat damage are prevented, thereby preventing secondary damage. Prevent disasters from occurring.

Next, a second embodiment will be explained according to FIGS. 7 and 8. Note that the same reference numerals are given to the same or corresponding configurations as those of the first embodiment, and the explanation thereof will be omitted.

In this embodiment, a ring-shaped intermediate electrode 21 attached to both ends of the insulating core 11 is arranged inwardly at the center.
A plurality of engagement pieces 22 bent in a letter shape connect to the insulating core 1.
1, and four projecting pieces 23 are provided on the outer periphery thereof and projecting at equal angles to each other. The bottomed cylindrical electrodes 24 and 25 that are placed on both ends of the insulating outer cylinder 1 have recesses 26 formed on their end faces corresponding to the projections 23 of the intermediate electrode 21.
The projecting piece 23 is exposed to the outside through a through hole provided on the side, and then bent into an L-shape.
Further, solder 27 is embedded in the recess 26.

The base end of the electrode rod 15 is fitted into the opening of the insulating core 11 via the engagement piece 22.
Further, a mounting plate 15a having a discharge hole 15b is attached to the base end of the electrode rod 15 by screwing.
A thin portion 20 is formed on the outer end surface of the electrode 25 corresponding to the discharge hole 15b.

Similarly, the base end of the electrode rod 14 is fitted into the opening of the insulating core 11 via the engaging piece 22, and
A mounting plate 14a with a discharge hole 14b at its base end
are integrated. Similarly, a thin portion 20 is formed on the outer end surface of the electrode 24 corresponding to the discharge hole 14b.

Therefore, in this second embodiment, when the pressure inside the insulating core 11 rises abnormally due to the interruption, the thin portions 20 of the electrodes 24, 25 are discharged through the discharge holes 14b, 15b provided in the electrode rods 14, 15. The current limiting fuse F will not be destroyed because the pressure will be released to the outside.

Other effects are similar to those of the first embodiment.

It should be noted that this invention is not limited to the above-mentioned embodiment; for example, the configuration of the second embodiment may be arbitrarily modified without departing from the spirit of this invention, such as omitting the discharge hole of one of the electrode rods. is also possible.

Effects of the device As detailed above, this device generates an arc in the discharge gap between the upper and lower electrode rods in advance of the external flash between the upper and lower contact blades that occurs in the current limiting fuse F when multiple lightning strikes occur. Furthermore, since this arc is reliably extinguished by the arc extinguishing tube, subsequent current can be reliably blocked.

Therefore, unlike conventional fuses, external flash does not occur in current-limiting fuses, and uneven heat damage to the high voltage cut-out due to external flash and scattering due to uneven heat damage are prevented, thereby preventing secondary disasters. This is an excellent invention for industrial use, as it has the effect of preventing the occurrence of gas and significantly increasing the safety of high-pressure cut-outs.

[Brief explanation of the drawing]

Fig. 1 is a front view of the high voltage cutout and the transformer connected, Fig. 2 is a sectional view of the current limiting fuse of the first embodiment, and Fig. 3 is a sectional view showing how the insulating core is attached to the insulating outer cylinder. 4 is a partial sectional view of the protective cover, FIG. 5 is a perspective view of the conductive plate, FIG. 6 is a partial perspective view of one electrode rod, FIG. 7 is a sectional view of the second embodiment, and FIG. The figure is also a side view. DESCRIPTION OF SYMBOLS 1...Insulating outer cylinder, 2...Upper contact blade, 3...Upper electrode fitting, 4...Lower electrode fitting, 5...Lower contact blade, 9...Intermediate electrode, 11...Insulating core, 13
... Fuse element, 14, 15 ... Electrode rod, 16 ... Discharge gap, 17 ... Arc extinguishing tube.

Claims (1)

[Scope of utility model registration request] In a current limiting fuse, an insulating core is provided between fixed electrodes fixed to both ends of an insulating outer cylinder, and a fuse element is wound around the outer periphery of the insulating core to electrically connect the two electrodes. A pair of electrode rods are electrically connected in parallel to the element, one end of which is connected to a fixed electrode, and the other ends of the electrode rods are arranged facing each other with a discharge gap, and an arc extinguishing tube is connected between the tips of the two electrode rods. A current-limiting fuse characterized by being covered with.