JPH0698449A - Gas-insulated expandable bus - Google Patents

Abstract

PURPOSE:To simplify the structure of a bus by a method wherein a seath current is conducted through bars connected in parallel at the outside of a bellows while a plurality of small holes for catching particles are provided on the lower part of a protecting seath in the bellows. CONSTITUTION:Both ends of a bellows type seath 31 of a gas-insulated expandable bus are connected to seathes 41 for the bus through a seath 32 for connecting bellows and connecting flanges 33. Seath current conducting bars 34, expandable at the bent part thereof, are connected in parallel at the outside of the connecting flanges 33 to bypass seath current. A protecting seath 35, consisting of a conductive material having a resistance to arc, are provided coaxially with a central conductor 9 at the inside of the bellows type seath 31 and one side is fixed to a metal 37 while a plurality of particle catching small holes 35a for catching particles are formed at the lower part of the protecting seath 35. The particles, generated in a gas-insulated expandable bus, are caught by the small holes 35a and reflecting of the same is prevented while arc, generated in the bellows, is conducted from the protecting case 35 to a grounded vessel. According to this method, the insulator withstand voltage of the bellows unit can be increased and a resistance to arc can also be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention requires a stretchable busbar for a gas-insulated switchgear, in particular, a structure for thermally and mechanically protecting a sheath against an arc generated by an electrical accident such as a ground fault. It relates to a telescopic busbar for a gas insulated switchgear.

[0002]

2. Description of the Related Art FIG. 7 shows a side view of a general gas insulated switchgear for one circuit. The main buses 8a and 8b, the circuit breaker 7, and the main equipment of the bushing 1 are connected by a branch bus 4.
Expansion and contraction busbars that can absorb the amount of expansion and contraction corresponding to the design amount are installed in various places in order to absorb the assembly tolerance between main equipment and the axial thermal expansion and contraction of branch busbars. The purpose of installing the gas-insulated expansion and contraction busbar is to absorb the undue vertical displacement of the foundation between the main equipment, and it is generally called a large excursion bellows. Since the structure of the sheath portion is basically the same, the axial expansion / contraction busbar will be described here. FIG. 6 shows a general structure of a gas insulated stretchable busbar. The main element is composed of a connecting flange 33 that is a connecting portion with the busbar sheath 41, a bellows-shaped sheath 31 of the expansion and contraction absorbing portion, and a bellows connecting sheath 32 that connects the connecting flange and the bellows sheath. A conductor 9 for passing a circuit current is arranged inside the gas-insulated expandable busbar container made of these, and the conductor and the container are insulated with an insulating gas (for example, SF ₆ gas) of 3 to 5 MPa under normal gauge pressure. It has been subjected. The conductor is mechanically supported by an insulating spacer or the like, but it is not described here. Depending on the configuration, the conductor 9 may be one (single-phase circuit) or three (three-phase circuit), but the configuration is the same for the gas-insulated stretchable busbar. When the electric current of the circuit is applied to the conductor 9,
The sheath current induced by this flows through the busbar sheath and the bellows-like sheath, but the bellows-like sheath is generally formed in a corrugated shape with a thin steel plate or stainless steel plate in order to improve elasticity. ing. For this reason, when a sheath current is applied, the temperature rises due to local overheating in the bellows-shaped sheath. For bar 34
Set up. Further, as described above, since the bellows-like sheath has low mechanical rigidity, the reinforcing ring 36 may be installed in some cases.

When an accident such as a ground fault occurs in the gas-insulated expandable bus bar having such a structure, the sheath is damaged by the internal arc, and the pressure of the internal insulating gas sharply rises at a high temperature to damage the sheath. A so-called burn-through phenomenon occurs in which an object is struck and blown outside. This phenomenon is extremely dangerous for maintenance personnel, and means for preventing the burn-through phenomenon is needed. As a means to prevent the burn-through phenomenon, it is possible to install an external pressure relief device or widen the gas compartment in order to suppress the rise in gas pressure, but there are difficulties in terms of economic efficiency and accident recovery, Increasing the thickness of the sheath is the simplest and most effective means. In the case of gas-insulated busbars and major equipment such as gas-insulated switchgear, mechanical rigidity is required, so even though the design thickness does not consider burn-through, the thickness is almost enough to withstand burn-through. In the case of the sheath for use, the thickness is inevitably thin for the purpose of its installation as described above, which is the weakest point portion against burn-through.

Conventionally, the burn-through phenomenon is often unclear in terms of phenomena, and many have not taken measures against the sheath for gas-insulated expandable busbars. For example,
The configurations shown in JP-A-55-155509 and JP-A-56-136442 are those in which the above-mentioned sheath current energizing bar is installed as a cylindrical container inside a bellows-shaped sheath (conductor side) and burn-through. It seems to be effective as a countermeasure, but in these configurations, a connecting flange was required to secure an effective cross-sectional area for energizing the sheath current, and the airtight surface of the insulating gas increased. In addition, there is a problem in that the structure of the current-carrying cylindrical bar also needs to be expandable and contractible, which makes the structure complicated.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas-insulated stretchable busbar having a small airtight surface and having a simple structure and having a burn-through countermeasure.

[0006]

According to the present invention, a sheath current-carrying bar and a protective sheath for burn-through are divided and the protective sheath is installed inside a bellows-shaped sheath.
The protective sheath does not require a connecting flange.

[0007]

[Function] The protective sheath supported by welding or bolt connection on the inside (conductor side) of the bellows-shaped sheath is an arc-resistant conductive material (for example, copper plate or steel plate coated with conductive paint). ), The arc generated in the gas-insulated busbar is circulated from the conductor through the protective sheath to the grounded container and does not damage the thin plate portion of the bellows-shaped sheath.

Further, by providing a small hole for capturing particles in the vertical lower part of the protective sheath, particles existing in the gas insulating bus bar and impairing the insulation performance are captured from the small hole between the protective sheath and the bellows-like sheath, Make sure that it cannot move again within the insulated busbar.

Since the protective sheath is fixed to the bellows-shaped sheath only on one side in the axial direction of the gas-insulated busbar, the bellows can be bellowed rather than the arc regardless of expansion and contraction of the gas-insulated expandable busbar and without requiring its own expansion / contraction device. Protect the sheath. Alternatively, by fixing two pieces of protective sheaths to one end of each bellows-like sheath, a protective sheath having the same function can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a gas-insulated stretchable busbar according to an embodiment of the present invention. The gas-insulated stretchable busbar is connected to a busbar sheath 41 or another equipment container via a connecting flange 33. On the other hand, the connecting flange 33 is integrally formed with the bellows-shaped sheath 31 by a welding structure or the like via a portion of the bellows connecting sheath 32 having a plate thickness generally similar to that of the busbar sheath 41. . The bellows-shaped sheath is formed in a corrugated shape, and a reinforcing ring 36 is arranged to increase rigidity. The sheath current energizing bar 34 is arranged at several places in the circumferential direction by bypassing the outside of the bellows-shaped sheath by bolt connection or the like from the flange portion of the busbar sheath. Therefore, the sheath current induced by the circuit current during normal operation flows between the busbar sheaths without passing through the bellows-shaped sheath. Ground potential sheath 41
Inside the bellows-shaped sheath 31, a high-voltage potential conductor 9 for passing a circuit current is arranged and insulated by an insulating gas 10. The protective sheath 35 is arranged inside (on the side facing the conductor) so as to protect the bellows-shaped sheath 31 by bolt connection to a protective sheath mounting member 37 installed in advance in the bellows connecting sheath 32 portion. FIG. 2 shows a connection example of the protective sheath connection portion. For the mounting portion of the protective sheath, it is better to take a counterbore to prevent the head of the bolt from traveling on the conductor side inner surface of the protective sheath. Is preferred. Protective mounting bracket 3
The number 7 is not limited to the entire circumference, and it is sufficient that the several positions are arranged uniformly in the circumferential direction to ensure a sufficient cross-sectional area for processing the arc current.

Assuming now that dielectric breakdown occurs from the conductor 9 and a ground fault current flows to the ground potential side, the busbar sheath 4
No. 1 is composed of a thick member that can withstand this ground fault current as described above, but there is no problem. However, when the protective sheath 35 is not provided, current flows through the thin bellows-shaped sheath 31 and burn-through. Generate. According to the invention,
Since the ground fault current flows through the conductive protective sheath 35 to the thick bellows connecting sheath 32, the bellows-shaped sheath can be protected from the arc and burn-through does not occur. The material of the protective sheath 35 may be a conductive member having a low resistance to a ground fault current, such as a copper material, or a member in which a conductive paint is applied to the surface of a metal material.

In FIG. 3, a small hole 35a for capturing particles is installed on the lower surface of the protective sheath 35 in the vertical direction. Particles (dust) generated at the time of assembly or from the sliding part of the switch are a major cause of impairing the dielectric strength of the insulating gas, but move in the metal sheath vibrating with the AC frequency. By providing a small hole in the protective sheath 35 that is slightly larger (about several mm) than the size of these conceivable particles, the particles that have moved can be captured. The captured particles are stored in the corrugated portion of the bellows sheath 31, but this portion has a small levitation electric field due to the influence of the protective sheath 35, and cannot escape again into the sheath through the small hole.

FIG. 4 shows a structure in which the protective sheath is integrally welded in advance in the gas-insulated expansion / contraction busbar, and is functionally the same as the embodiment of FIG. If the gas-insulated expandable busbar is large, the protective sheath becomes a heavy object. Therefore, if there is a difficulty in assembling the protective sheath in the gas-insulated expandable busbar, it is desirable to have such an integral structure. Also, if there is a problem in strength with a cantilever structure where there is only one welding or bolt connection, the protective sheath is divided into two pieces as shown in Fig. 5 and they are connected to each other to leave a gap. It is also possible to configure so that expansion and contraction of the insulating expansion and contraction busbar can be dealt with.

[0015]

According to the present invention, since the sheath current carrying bar and the protective sheath of the gas-insulated stretchable busbar are separated and the protective sheath is arranged inside the bellows-shaped sheath, a structure such as an expandable portion is not required. As a result, the gas-insulated expandable bus bar can be provided with a burn-through countermeasure that does not increase the gas-tight surface and has a simple structure. In addition, it is possible to combine the particle capturing function by simply providing a small hole in the protective sheath.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a gas-insulated stretchable bus bar according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of FIG.

FIG. 3 is a cross-sectional view of a gas-insulated stretchable bus bar according to an embodiment of the present invention.

FIG. 4 is a sectional view of a gas-insulated stretchable bus bar according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view of a gas-insulated stretchable bus bar according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional gas-insulated stretchable bus bar.

FIG. 7 is a side view of one line of a gas-insulated switchgear that uses a gas-insulated stretchable busbar.

[Explanation of symbols]

9 ... Conductor, 10 ... Insulating gas, 31 ... Bellows-like sheath, 32 ... Bellows connecting sheath, 33 ... Connection flange, 34 ... Sheath current energizing bar, 35 ... Protective sheath,
35a ... Small holes for capturing particles, 36 ... Reinforcing ring, 37 ... Protective sheath mounting bracket, 41 ... Busbar sheath.

Claims (4)

[Claims] 1. A gas-insulated busbar comprising an expandable and contractible bellows-like sheath in which an insulating gas is sealed and a conductor arranged in the bellows-like sheath. An arc-resistant conductive material is provided inside the bellows-like sheath. A gas-insulated stretchable busbar, which is provided with a protective sheath made of. 2. The gas-insulated stretchable bus bar according to claim 1, wherein a plurality of holes for capturing particles are provided in a lower portion of the protective sheath. 3. The gas-insulated expandable bus bar according to claim 1, wherein the protective sheath is fixed only on one side in the axial direction of the bellows-shaped sheath so as to be capable of expanding and contracting the bellows-shaped sheath. 4. The bellows-like sheath according to claim 1, wherein two pieces of protective sheaths are fixed to the flanges on both sides of the bellows-like sheath so that expansion and contraction of the bellows-like sheath can be accommodated.
A gas-insulated telescopic busbar with a gap between the protective sheaths of the pieces.