JPS6241523Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an arc protection device for closed electrical devices such as closed switchboards.

If a short-circuit accident such as a short-circuit between phases occurs inside a closed type switchboard, and an arc is generated, the arc energy causes the inside of the panel to rise in pressure and become filled with high-temperature gas, causing damage to internal equipment. Of course, the ground metal plates that partition the interior, such as bulkheads and outer coverings, may melt and create holes, and if there are people nearby at such times, they may be exposed to water erupting from the holes. This is extremely dangerous as it will melt the high temperature gas. The locations where the ground metal plate is damaged are generally located near the final end of the electrical circuit on the side opposite to the power source, for example, near the protruding part such as the end of the conductor. Three-phase conductors 1 arranged in parallel as shown
This is because the short-circuit point F of 01 instantaneously shifts to the opposite side of the power source and is eliminated by the ground fault caused by the partition wall 102 which is at the ground potential near the terminal end. However, this was not perceivable from the outside or from the other side of the bulkhead, a drawback common to closed electrical devices.

In view of the above, it is an object of this invention to provide an arc protection device for a closed electrical device, which reduces damage to the bulkhead and the outer sheath and improves safety even if an arc occurs due to a short-circuit accident or the like.

According to this invention, the above-mentioned purpose is to connect electrical circuits that are made up of electrical equipment and conductors installed inside a closed box body and expose bare live parts everywhere, and to connect grounded metal plates such as bulkheads and outer sheaths that partition the inside of the box body. In a device for reducing damage to the ground metal plate caused by arcing in the event of a short circuit accident within the box, the ground metal plate is located at least opposite to a bare live part that is the final end of the electrical circuit on the side opposite to the power source. This can be achieved by providing metal fittings at certain locations with a predetermined insulating distance and facing each other at a distance smaller than the insulating distance between any of the bare live parts of the electrical circuit and the ground metal plate.

Examples of this invention will be described below based on the drawings. FIGS. 2 and 4 show a closed power distribution board for a power supply circuit configured according to the single line diagram shown in FIG. It is divided by the partition wall 2 and partition plates 3, 4, and 5 located in the power position into an instrument room 1a and a power disconnection room 1b on the front side, and a busbar room 1c and a cable room 1d on the rear side. There is. Although not shown in the diagram, the instrument room 1a houses monitoring instruments, watt-hour meters, protective relays, etc., and the disconnector chamber 1b houses a drawer-type disconnector 6.
A three-phase bus 7 is housed in c, and an instrument current transformer 8, terminals 9, etc. are housed in cable room 1d. The partition wall 2 is provided with female disconnection contacts 10a and 10b that can be connected to and separated from the male disconnection contacts 6a and 6b provided behind the shield and disconnector 6, and the upper female disconnection contact 10a is connected. Conductors 11a, 11b, 11
The lower female disconnecting contact 10b is connected to the bus bar 7 via a current transformer 8, and to the terminal 9 via a current transformer 8. 3 shown as A, B, and C in Figure 3.
The corresponding part of the partition plate 5 facing the lower end of the connecting conductors 11a, 11b, 11c, which is the final end on the opposite power side of the busbar chamber 1c, and the male terminal, which is the final end on the opposite power side of the disconnector chamber 1b, The relevant part of the partition wall 2 facing the corner of the side disconnection contact 6b and the relevant part of the back cover 13 facing the terminal 12a of the cable 12 connected to the terminal 9 at the final end on the side opposite to the power source of the cable room 1d. Arc hardware 14 is integrated at each location by welding. The hardware 14 is formed into a U-shape by bending a band iron, and is kept at a predetermined insulation distance l1 from the corresponding bare live part, and protrudes from the plate surface with respect to the attached ground metal plate. It is installed as follows. In other words, although a predetermined value is secured for the insulation distance l1 between the three metal fittings 14, there is a distance between bare live parts such as other conductors constituting the electric circuit and the partition wall 2, partition plates 3, 4, 5, and the outer sheath 13. This is smaller than the insulation distance l between the ground metal plate and the ground metal plate. Therefore, as described above, the arc generated by the short circuit runs toward the opposite side of the power source and is extinguished by the ground fault.
Since the metal fittings 14 are provided in each of the compartments d and each is attached to the final opposite side of the power supply in the compartment, most arcs caused by short-circuit accidents are extinguished within the room where the accident occurred. At that time, the metal fittings 14 will be damaged by melting, etc., but damage to the bulkheads, partition plates, outer coverings, and other grounded metal plates will be greatly reduced, and holes will be made and hot gas will be blown out, resulting in personal injury. I can hardly think of anything that would cause this. In addition, although the closed type switchboard was described above as an example, it goes without saying that it is applicable to other switching devices housed in a closed type box.

As described above, according to this invention, a predetermined insulation distance is secured facing the final bare live part on the side opposite to the power source of the electrical circuit that constitutes the device, but it is less than the distance between other bare live parts and the ground potential. Safety can be greatly improved with a simple configuration of just installing a metal object with ground potential over a short distance, so we can expect an increase in demand if it is adopted.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram that led to this idea, Figure 2
Figures 4 to 4 are diagrams showing one embodiment of the arc protection device for a closed type switchboard according to this invention, and the second
The figure is a side sectional view thereof, FIG. 3 is a single line diagram thereof, and FIG. 4 is an enlarged sectional view taken along the - line in FIG. 2. 1... Closed box body, 2... Partition wall, 3, 4, 5...
...Partition plate, 6...Drawer shape and disconnector, 7...Bus bar,
8...Current transformer, 9...Terminal, 11a, 11b, 1
1c... Connection conductor, 13... Outer cover, 14... Hardware.

Claims (1)

[Scope of utility model registration request] An electrical circuit is installed between an electric circuit that is made of electrical equipment or conductors installed in a closed box body and shows bare live parts everywhere, and a grounded metal plate such as a bulkhead or outer cover that partitions the box body. A device for reducing damage to the ground metal plate due to an arc in the event of a short-circuit accident, the device comprising: a predetermined insulation at least at a portion of the ground metal plate facing a bare live part that is the final end on the side opposite to the power source of the electric circuit; 1. An arc protection device for a closed electric device, characterized in that metal objects are provided at a distance and facing each other at a distance smaller than the insulation distance between any of the bare live parts of the electric circuit and the ground metal plate.