JPH0157481B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pull-out arrester that has an improved grounding terminal that connects to and exits electrical equipment.

Arresters are generally installed between electrical equipment and the ground, and when an abnormal voltage occurs from the power supply circuit to the load circuit, it forms a ground circuit between the circuit and the ground, and the electrical discharge that passes through it forms a ground circuit. , the peak value of abnormal voltage is reduced to prevent damage to electrical equipment. One possible method of attaching an arrester to electrical equipment is a retractable arrester, in which the arrester is inserted into and removed from the electrical equipment. A retractable arrester has a main circuit terminal and a ground terminal, like a general arrester.

When the arrester is inserted into the electrical equipment, each of these terminals electrically closes the fixed main circuit contact and the fixed ground contact provided in the electrical equipment. When the arrester is pulled out from the electrical equipment, there is a position where the main circuit terminal is separated from the fixed side main circuit contactor and a position where the ground terminal is separated from the fixed side ground terminal. In the former position, since ground capacitance exists, the potential on the main circuit side applies the arrester via the ground capacitance, and the arrester is in a high potential state.

However, in the latter case, the ground terminal is not grounded, so the high potential of the arrester cannot be released to the ground circuit via the ground terminal. For this reason,
Workers who grasp the high-potential arrester may receive an electric shock. Also, when inserting an arrester, there is a risk of electric shock as described above.

An object of the present invention is to provide a pull-out arrester that is safe when the arrester is inserted into and removed from electrical equipment.

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment of the present invention will be explained using a closed switchboard 1 shown in FIG.

The switchboard 2 forms a busbar chamber 4 and a disconnector chamber 5 via a partition wall 3 provided therein. The busbar chamber 4 has a load busbar 6 and a power supply busbar 7 disposed therein, and the load busbar 6 passes through the inside of the current transformer 8 . One end of the load bus 6 and the power supply bus 7 is connected to a fixed disconnecting section 9 supported by the partition wall 3 . The end of the fixed disconnector 9 on the side of the shield breaker chamber is connected to main contacts 10A and 10B of a shield breaker 10, for example, a vacuum shield breaker. The shield disconnector 10 moves into and out of the shield disconnector chamber 5, thereby coming into contact with and separating from the fixed disconnecting section 9. A pull-out arrester 12 is disposed on the lower partition wall 3 of the lower fixed disconnection section 9A connected to the load bus bar 6.

Details of the pull-out arrester 12 will be explained with reference to FIG. 2A. External insulation tube 1 attached to bulkhead 3
3 is a fixed terminal 14 which is a fixed side main circuit terminal attached to one end, and a connecting conductor 15 is connected by a screw 15A.
Install. The connection conductor 15 is connected to the load bus 6. At the end of the external insulation pipe and on the inner wall surface, there is a
A metal layer 16 is provided. Arranged within the external insulating cylinder is an arrester element 17, such as a non-linear resistance element such as zinc oxide or nickel oxide. The arrester element 17 is housed in an internal insulating cylinder 19 having a metallic internal terminal 18 at one end. (The internal terminal 18 is connected to the fixed terminal 14 via the spring 20.) The other end of the internal insulating cylinder 19 is connected to the pressing spring 21.
A metal cap 22 is removably attached via the cap. Second metal layer 2 formed on the outer periphery of the internal insulating cylinder
3 is in contact with the first metal layer 16 and the metal cap 22. First and second metal layers 16, 23
is connected to a ground terminal 24 which is a fixed side ground terminal provided between the metal cap 22 and the external insulating cylinder 13. Insertion hole 25 formed in metal cap 22
Insert the screw 26 into the ground terminal 24 and the external insulating tube 1 by tightening the screw 26
3. It can be removed and attached freely. The ground terminal 24 is connected to the ground E via a lead wire.

Next, the case where the pull-out arrester 12 is moved in and out of the external insulating cylinder 13 will be explained with reference to FIGS. 3A and 3B.

The internal terminal 18 of the pull-out arrester 12 is the third A
As shown in the figure, the second metal layer 23 is in contact with the fixed terminal 14 and is grounded via the first metal layer 16, in a so-called operating state. In this state, the internal terminal 18 separates from the fixed terminal 14, and the second metal layer 23
Move to the disconnection position of FIG. 3B in contact with metal layer 16.

That is, as can be seen from FIG. 3B, the time that the first metal layer 23 is in contact with the second metal layer 16 is longer than the time that the internal terminal 18 and the fixed terminal 14 are in contact with each other. . In other words, the contact length is longer on the first metal layer side than on the internal terminal side. Therefore, in the disconnection position, the potential on the connecting conductor side is applied to the draw-out arrester 12 via the capacitance C existing between the fixed terminal 14 and the internal terminal 18, but the arrester Since the high potential flows to the ground E via the second metal layer 23 and the first metal layer 16, the pull-out arrester 12 cannot maintain a high potential state. Therefore, it is safe for the worker to avoid receiving an electric shock when pulling out the pull-out arrester 12. Further, when inserting the pull-out type arrester into the external insulating cylinder, the process is exactly the same as described above.

Further, the drawer-type arrester 12 of the present invention has a simple structure and can be applied to existing closed switchboards, since the first metal layer 23 may be provided on the outer periphery of the internal insulating cylinder 19. In this case, instead of the first and second metal layers, a tube made of a metal member may be fitted into the outer insulating tube and the inner insulating tube. Particularly, the tube to be fitted into the internal insulating tube can be easily fitted into the inner insulating tube if its tip is divided into a plurality of pieces with a space between them.

As described above, the pull-out arrester of the present invention is safe and has a simple structure.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a closed switchboard shown as an embodiment of the present invention, Fig. 2A is a side sectional view of the pull-out type arrester used in Fig. 1, and Fig. 2B is a side sectional view of the arrester element shown in Fig. 2A. Figures 3A to 3
Figure B is an equivalent circuit of Figure 1. 12...Pull-out arrester, 13...External insulation cylinder,
14... Fixed terminal, 23... First metal layer, 24... Ground terminal.

Claims (1)

[Claims] 1. An insulating tube having an opening at one end, a fixed terminal and a grounding terminal provided at one end of the insulating tube, and a drawer-type arrester that connects and separates from both terminals into and out of the insulating tube, wherein the drawer-type arrester A draw-out type arrester, characterized in that a metal member is provided on the outer periphery of the metal member that makes contact with and separates from the ground terminal.