JPS633077Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a protection device for electrical equipment, and in particular, when a fault current that has a large difference from the rated current occurs in the electrical equipment, the fault current is suppressed by melting the fusible conductor. This invention relates to a protection device for electrical equipment that is cut off.

In the event of an accident involving electrical equipment, if there is a large difference between the rated current of the equipment and the fault current, the fault current is removed using a fusible conductor as a protective device for the equipment. A well-known method is to use thermal energy to detect accidents. For example, there is a protection device against a short-circuit accident between taps due to a failure to interrupt the main arc contact of a tap changer under load. FIG. 1 shows a schematic structure of a well-known on-load tap changer, in which 1 is a container for a changeover switch 2, 3 is a tap selector, 4 is a transformer tank, 5 is an oil flow relay, 6 is a conservator, and 7 is a tap selector.
8 is a piping, 8 is an outer insulating cylinder which is a main component of the container 1, 9 is a pressure relief device, and 10 is a protection device using a fusible conductor. Figure 2 shows an example of the circuit of this type of on-load tap changer, where 11 is the transformer tap winding, 12 is the odd-numbered current-carrying contact, 13 is the odd-numbered main arc contact, 14 is the resistance contact, and 15 is the even numbered contact. side main arc contact, 16 is even number side energizing contact, 17 is current limiting resistor,
18 is a fusible conductor, 19 is a tap in use, and 20 is a tap to be used next. FIG. 3 shows the switching sequence of each switch in the circuit of FIG. 2, and the symbols in the figure are the same as in FIG.

Now, in the switching process from taps 19 to 20, if the odd-numbered side main arc contact 13 fails to break for some reason and the broken arc continues until the even-numbered side main arc contact 15 is closed (ON),
A closed loop circuit is formed between taps 19 and 20 in which no current limiting element is inserted, and the distance between the taps is determined by the voltage induced between taps 19 and 20 and the slight impedance within the closed loop. A short circuit current will flow.
This short-circuit current has a value of tens to hundreds of times the rated current and instantly melts the two fusible conductors 18 connected in series between the closed loops, and the current continues to flow through the arc. It disappears when the dielectric strength of the fusing gap exceeds the voltage applied between the fusible conductors. On the other hand, during the process from this fusing to the extinction of the arc, the surrounding insulating oil, which is an insulating medium, is decomposed and gasified by the arc energy. As a result, the internal pressure of the container 1 of the switching switch 2 shown in FIG. It flows out. This oil flow causes the oil flow relay 5 to operate, and an abnormality in the switching switch 2 is detected.
When the pressure inside the container 1 further increases, the pressure relief device 9
operates to prevent destruction of the container 1, that is, the outer insulating cylinder 8.

Therefore, the fusible conductor 18 used in this protective device must satisfy the following requirements.

(a) Fault current can be removed quickly without damaging the transformer coil.

(b) Minimize damage to the main components of the switching switch 2 and container 1 as much as possible.

Conventionally, as a structure of a fusible conductor that satisfies the above two requirements at the same time, there has been a structure in which the fusible conductor is surrounded by an insulating tube. This differs from the method in which a fusible conductor is covered with an insulating tube to insulate it from other conductors, and the fused part of the fusible conductor is surrounded by an insulating tube to form an arc confinement space. In other words, it is a well-known phenomenon that when an arc is confined in a confined space, the arc resistance in the space increases and the arc becomes more easily extinguished, and the configuration in which a fusible conductor is surrounded by an insulating tube embodies this phenomenon. This is one method, and with this configuration, short-circuit current between taps, that is, fault current can be removed more quickly. Furthermore, if the insulator near the fusible conductor is made of a material that generates arc-extinguishing gas, the ability of the fusible conductor to interrupt fault currents will further increase.

Further, as can be seen from FIG. 1, not only is the outer insulating tube 8 disposed close to the protective device 10, but also the fusible conductor 18 attached to the protective device 10 is fused due to the fault current and heats the surrounding insulating oil. It is often subjected to the impact pressure generated when it is disassembled, perpendicular to its surface. In the case of the protection device 10 having such an arrangement,
A shield is provided between the fusible conductor 18 and the outer insulating cylinder 8,
It is very significant to prevent the outer insulating cylinder 8 from receiving the impact pressure at right angles to the surface as much as possible when the fusible conductor melts, from the viewpoint of reducing damage to the outer insulating cylinder. The configuration in which the fusible conductor is surrounded by an insulating tube allows the insulating tube to function as the shield, and can be said to be an effective means for reducing damage to the outer insulating tube.

This invention is based on the fact that by surrounding a fusible conductor with an insulating tube, a very effective protective device for electrical equipment can be obtained, as described above. The purpose is to provide a protection device for electrical equipment with a very simple structure.

An embodiment of this invention will be described below with reference to the drawings. 4, 5, and 6, the plate-shaped fusible conductor 21 used in the protection device has a plate thickness t,
It has a rectangular shape with a width w, and holes 23 are formed on both sides of a slit 22 in the center, and the parts where the slit 22 and holes 23, which have a partially reduced cross-sectional area, are provided are sequentially fused due to the fault current. It is structured to do this. The fusible conductor 21 is fixed to a suitable support (not shown) via an insulating mounting plate 24. The fusible conductor 21 is fastened with a drawer lead 25, a double end bolt 26, and a nut 27, and is further attached to an insulating mounting plate 24 with a nut 28. The cylindrical insulating tube 29 has an inner diameter d and a length l, surrounds the fusing part of the fusible conductor 21, and is attached to the insulating mounting plate 2.
4 is fitted. Therefore, the insulating mounting plate 24 is formed with an opening 30 having a length L in the longitudinal direction of the fusible conductor 21 and holding both end faces of the insulating tube 29 between opposite sides thereof. Reference numeral 8 indicates the above-mentioned outer insulating cylinder, which is a main component of the switching switch container.

With the above configuration, the insulating tube 29 has the plate-shaped fusible conductor 21 passing through the inside thereof, so that the plate-shaped fusible conductor 21 itself prevents the plate-shaped fusible conductor 21 from falling off in the thickness and width directions. Furthermore, since the insulating tube 29 is fitted with the insulating mounting plate 24, movement of the plate-shaped fusible conductor 21 in the length direction is restricted, and the fused portion of the fusible conductor is not exposed.

As described above, the plate-shaped fusible conductor 21 and the insulating mounting plate 2
4, the insulating tube 29 can be easily fixed without providing any other fittings. Furthermore, a plate-shaped soluble conductor 2
Since the fusing part 1 is surrounded by the insulating tube 29, the fault current interrupting ability of the fusible conductor is higher than in the case where there is no insulating tube.

In addition, since the insulating tube 29 serves as a shield between the outer insulating tube 8 and the plate-shaped fusible conductor 21, the outer insulating tube 8 does not receive the impact pressure generated when the fusible conductor melts at right angles to the surface. , damage to the outer insulating cylinder 8 can be prevented.

Note that if the insulators near the plate-shaped fusible conductor 21, that is, the insulating tube 29 and the insulating mounting plate 24, are made of a material that generates arc-extinguishing gas, the fault current interrupting ability of the fusible conductor will be increased.

As mentioned above, the following effects can be obtained by this invention.

(a) The fusible conductor and insulating mounting plate allow the insulating tube to be mounted and fixed without the need for any other fittings.

(b) The fault current interruption capability is improved, enabling fault current to be removed more quickly.

(c) Damage to the components, such as the outer insulating tube, in the vicinity of the fused portion is not affected perpendicularly to the impact pressure generated when the fusible conductor is fused, so damage to the components can be prevented.

(d) The protection and detection reliability of the protective device is increased.

[Brief explanation of the drawing]

Fig. 1 is an elevational view showing a schematic configuration of a conventional on-load tap changer, Fig. 2 is a wiring diagram showing an example of the on-load tap changer circuit, and Fig. 3 shows each of the circuits in the circuit system of Fig. 2. 4 is a plan view of an embodiment of the invention, FIG. 5 is a cross-sectional view taken from FIG. 4, and FIG. 6 is a cross-sectional view taken from FIG. 4. 8... Outer insulating tube, 21... Plate-shaped fusible conductor, 22
... slit, 23 ... hole, 24 ... insulation mounting plate, 25 ... drawer lead, 29 ... insulation tube, 30 ... opening. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Utility Model Claims] (1) A protection device for an electric device comprising a plate-shaped fusible conductor provided with a fusing portion that melts when subjected to a fault current, an insulating tube surrounding the fusing portion to form an arc containment space, and an insulating mounting plate supporting the plate-shaped fusible conductor, characterized in that the insulating mounting plate has an opening for receiving and supporting the insulating tube. (2) A protection device for an electric device as set forth in Utility Model Claim 1, in which both end faces of the insulating tube are clamped and supported by opposite sides of the opening. (3) A protection device for an electric device as set forth in Utility Model Claim 1, in which the insulating mounting plate is made of an insulating material that generates an arc-extinguishing gas.